I've found that out myself. If you have an idea you think will work, and then it turns out this idea "doesn't work," when you finally figure out why this idea "doesn't work," you still learn something in the process.
I had a similar problem with a Pro16 car in 2002, 35 psi boost on a 2 liter Honda motor (ACT sponsored car for the 2002 NOPI nationals). It was making 300 HP at the wheel... and nothing made it better. Hours later they finally asked me to take a shot at tuning it, mostly because I was ready to shut down for the night. Quickly realized that something was wrong with the ignition system (insufficient amps to run it). Added a second battery, pulled, 400 WHP. 1 hour of tuning later, 620 WHP on a 2.0 liter Honda... which took the class at LACR that year (edit: it might have been 2nd place).
@@strydyrhellzrydyr1345 ya, same engine, same parts, same dyno session. Still have the signed photo from the team thanking me. I tell you what, track down Jojo Callos and ask him yourself. We were on the dyno way past midnight on Friday before the qualifiers. A badly functioning ignition system will do exactly that much damage to your power. It was a Crane Hi-7 system which draws an inordinate amount of power and requires very specific wiring to operate correctly. It was also the first MOTEC system that I had tuned. Doubt it all you want. I had failures too, like the time I calculated out (and built) what I thought was the perfect intake and exhaust system (promptly losing 50 HP) over baseline on a 13B rotary. Finally threw away the intake, and was able to pick up power, but I was humbled. There were motors I couldn't find any power, but usually, if I was going to find a bunch of power - it was on the ignition side of the equation.
The 350 mystery....rocker type, and ratio? "Beehive", conical springs? You stated that he ported the heads himself. Assuming you weren't standing there over his shoulder the entire time, maybe he milled them, as well. Enough to bump the compression ratio closer to 11:1. You probably still have the spec sheet for the cam grind he ordered. Do those specs have room that would favor a half point more in compression? What header tube diameter was that engine running? There are some many tiny variables, that it's not surprising that the AD Dominator only ran perfectly on that particular build. Anyway, I have to say that this was one of the most enjoyable videos that you've made here on your channel, Mr. Vizard. I could sit and listen to your stories for hours on end. Please consider making more in depth videos, recounting your past life experiences in racing, and the engines you built for those paricular races. These stories are NOT "boring!" Sorry for the novel. But my Dad was a drag racer in San Antonio, TX., in the 1960s. And a great race engine builder in his own right. He's gone now, and I wish I had the presence of mind to document (video record), his stories behind the boxes of drag racing trophies I found after he passed away. So please, tell us all of yours. With much respect. ❤
A mistake is a chance to learn something new. A success is just a confirmation of what you already knew. I think both have their place, but figuring out how to fix a mistake can be so much more rewarding!
I put new different brand sparkplugs in the 351W engine in my boat and it wouldn't start... put the old worn out sparkplugs back in and it started right up... looking closely at the new plugs, the steel body shell of the plug stuck out much further beyond the threads and was apparently shrouding the spark too much...
Had NHRA Stock Eliminator AMC AMX that wouldn’t respond to ANY tuning changes. Up this this point, tuning changes had always worked. Then as R&D made more HP, it hit a wall. Put significantly colder race plugs in and everything worked again. This was a record holding car.
well David i am going out on a limb here on the why the carb worked on that 350 engine ,,, the ported heads , the total seal rings, and the solid lifter cam ,,, made that carb think it was on a big block because it was moving enough air to work in the lower rpm range ,,, thats my thought in a nut shell ,,, David so glad you take the time to teach us what we dont no THANKS TONY
I have built many street engines in my life so far. Most ran pretty good. I ALWAYS learn something valuable watching your videos. Thank you for sharing so much of your knowledge and experience!
With regard to the Mini engine more fuel vapor in the intake charge results in less airflow. Air flows best without liquid in it. That engine where the Dominator worked well probably had excellent port velocity increasing the signal to the boosters.The chamber shape of that EQ head is very efficient with optimal swirl and power production. And the iron head harnesses more heat energy. Add in optimal quench clearance, your porting tricks and properly spec’d cam and you get more low end torque than those other engines where the Dominator didn’t work well.
On the spark plug dilemma, I have a 2-stroke dirt bike and I keep spare spark plugs handy. All of those plugs are different. There are AC Delco, Autolite, Champion, Motorcraft and NGK. All ARE properly match-spec'd for the bike. These spark plugs do NOT perform identically, and one stands out magnanimously over all others. I will always try different spark plugs in whatever engine because of this.
Being a motorcycle mechanic 'forever' the only theory I can come up with is for the Mini engine conventional vs 'race' plugs. Probably explained by the way the fuel/air was flowing over the plug end, spark kernel and flame propagation. In effect, the mixture wasn't getting into the spark gap properly so burn was delayed.with max cylinder pressure happening too far into piston travel. That would show up on gas analyser as OK burn but wouldn't be producing power(possibly continuing to burn in exhaust manifold or pipe? did you check temperatures?) I remember reading about something similar when surface discharge plugs for a Suzuki RE5 rotary were fitted to a conventional engine as an experiment due to conventional plugs overheating. Shortening side electrode for a shorter heat path seemed to help (NGK made special short side electrode plugs for racing at one time, no idea if they still make them?) Last NGK catalogue I saw them in was around 1979 when 'real' work got in the way of playing with engines
The music at the end for some reason(that I can’t explain) is very powerful emotionally. Excellent information as usual even if I am just a noob when it comes to engine building/performance
I always said "there's dog engines and freak engines"...Built two specifically the same and there's one dog and one freak...Yep seen it done it...Good stuff Dave.
I like how you said the Dyno supports your findings and not proves it. Great video Thank you for sharing some here knowledge I love mystery builds that you just can't explain makes you think.
The over-atomized fuel made less power because the fuel displaced the air in the intake, you want the fuel to vaporize just as the intake valve closes so it doesn't take up space in the intake charge. Liquid fuel is much denser than vaporized fuel, having it be still a liquid in the intake charge increases volumetric efficiency.
Hello Mr. Vizard; I was hoping you could address a question I commented in your recent unequal length header video... 1.) Please assume an engine that produces peak horsepower @ 6500-RPM or less (if responding to Q#'s 2 & 3). 2.) Would you apply the (SAME +/- 4") primary lengths changes if the header were a 4-2-1 design vs. 4-1 design? 3.) Would a 4-2-1 header be superior to a 4-1 header given both had "ideal" / customized header primary lengths? Any feedback you're willing to provide is GREATLY appreciated; keep up the good work!!! 👍
Regarding the Dominator only working down low on the one engine, my wild guess is that reversion pulses weren't striking the carburetor base as strongly on that one. Maybe something in the intake tract reduced reversion (or the pulses got somewhat cancelled by each other) or the carburetor was positioned a little higher (spacer or taller plenum?) Interesting stuff.
Found out in my young years that , sometimes a engine would actually run real well And sometimes you put time and money into one and it just don’t do that well
A conventional spark plug with an "L" shaped electrode can shield a tiny volume of fuel/air mixture tightly around the spark allowing it to ignite better, causing a hotter more rapid flame travel and more complete combustion, leading to more power and better throttle response! PS; as compared to an open electrode type racing spark plug.
@@logan_e you mean an "L" shaped ground strap. The electrode is in the middle and is the "jumping off" point of the spark. Common to get those mixed up.
@@joe-hp4nk I like it- what is your preference? do you index the ground strap towards the intake valve to create an "umbrella" for the incoming charge or index it the opposite way so that the spark is completely exposed and open to the charge coming from the intake valve?
David, also curious if you experimented with intake plenum Helmholtz resonators? I’d seen them on many passenger cars for noise attenuation, also the benefit of engine tuning.
On engine number one, you might have put a set of different dyno headers on that had some internal rust forming on the pipe interior surface. Smoky Unich told a story about how he lost a bunch of power by doing this !
Great episode DV, makes me feel good to know that even with all your dyno time and tuning experience there are some mysteries that we mortals cannot explain. There's sometimes just too much going on in there to explain it.
For the "droplet" problem... this shows up all the time in EFI applications. Some engines and manifold combos seem to favor relatively large droplets and others want relatively fine droplets. Might be that the wave action actually favors a certain droplet size, and it might also be that the smaller droplet sizes need a higher compression ratio to work as well. One is always messing with the actual, effective air density of the intake charge in some way when droplet sizes are messed with, and if the actual effective air density goes down, then the engine will want a higher compression to make the same or more power than the old set-up that had a higher density with a lower compression... this is exactly the reason why D.I. engines make a lot more power than the same engine with only port injection does with dry, light air all the way to the cylinder. They run a much higher compression to compensate for the lower density of the intake charge!
That reminds me of Gail Banks, built a super charged engine, with a good bit of boost, made exactly the same power as without boost! Haha all the heat and loss of efficiency, Yeah sometimes you just don't know what little thing will throw a wrench into the worx! 🔧
#1 was hilarious. It reminded me of a story I read in a book of a particular class of steam locomotive where all members bar 1 performed to spec. The recalcitrant loco was the subject of much investigation and extensive modification none of which made the slightest difference.
There have been reports from firemen of identical steam locomotives that have different firing and operating characteristics even though the same coal was used. Some were easy to fire and others were difficult to fire yet had the same boilers and fire boxes. One of those odd things.🤨
Worked on an engine program for an OEM where the last improvement/optimization caused the engine to lose all previous gains. The engine program was canceled at the cost of millions of dollars lost. Also worked on vibratory feeding systems. Sometimes in the tuning process a "high Q" combination could be achieved, after steady small increments were implemented, that suddenly out produced the previous iteration by a profoundly wide margin. Turn the system off, come back the next day, and the numbers went straight into the toilet.
@@logan_e One source of variation learned late was that the springs on the vibrators were made of fiberglass reinforced plastic which had a 'memory'. They literally changed their spring rate after sitting overnight!
Had a 451” Big Block Mopar Drag car. New engine. No dyno time. First pas went 10.70 @ 125 MPH. Friends were ecstatic. I was not. I just did not pull in high gear (a PG trans). I went up 2 jet sizes in the 4150 Holley. Next pass: 10.02 @ 132 MPH and pulled like a freight train! Most say BS. Just dramatizes being on the wrong side of lean jetting. Never hanged jets again.
Your the best at explaining the process of the work you do on these engines......were going to soulth carolina this weekend i wouldnt mind stopping by to shake your hand and say thank you in person.....any way thank you....im in the process of doing a 350 sbc bulid.......i will use the tips your passing out to us......
In the case of the student designed and built motor, you stated several head porters could not believe the flow numbers. Those 1050s flow what, 1000 CFM of air, or more? A lesser 350 could not handle the amount of air and fuel being thrown at it, so it spits some back out! I believe flow is the answer.
For #2, the only thing that makes any sense at all is that the conventional type plug repositioned the start of the burn in a more favorable spot of the charge. We always assume that the charge at the point of combustion is going to homogenious enough to get all the power that can be had, but this is a simplification and can be wildly off from reality!! especially if this was a carbed forced induction engine... the fuel air ratios for individual cylinders can be all over the place but average out to give a good AFR reading at the tailpipe, and worse than that, the in cylinder AFR's and the point of combustion can be all over the place as well and still average out.
A thought on that mystery did you offset the grind on the rods throws to increase the stroke that could help with the Piston speed to increase your air volume down low on the rpm to make that large carb respond.
I would have never guessed you could loose half the engines power with just spark plugs without the thing exhibiting missfiring. Was it half power across the rev band or mostly at the hp peak? The dynamics of an engine are an insanely complex thing. Even 100 years after their invention accurate modeling of the entire engine is difficult to do. Sometimes things defy convention.
I wonder what the manifold vacuum was under the carb on the mystery 350 vs the ones it didn't like. I'm not a professional engine builder but thinking out loud I wonder if it wasn't a combination of cam timing and the plenum and entry to the ports in the intake being the perfect storm to make it work.
So much detailed attention is paid to the intake manifold, cylinder heads, and headers, seems like the one element of a NA engine that I think should be examined is the carburetor throats. The throats are close together and some models are built with sharp edges. Velocity stacks don't do much to remedy pulse interferences. Maybe some hp could be gained if the right individual stack design were developed.
Larger droplets & more power? I'd be thinking flame propagation slowed down a touch, and a few extra degrees of crank rotation were found close to peak cylinder pressure. Petrol does not burn until it finds air.
Exactly! You said it so much more simply than I did, lol I got a bit lost in the details but I agree! Larger droplets have less surface area but more volume, that takes slightly longer to burn, keeping more pressure longer into the power stroke; more torque = more horsepower!
@@V8Lenny Vapor can be a complex matter to manage: a fluid is somewhere between between being all liquid and all gas. Finding the sweet spot for power or mileage usually don't coincide. Having the correct amount of heat in the engine can make a difference. Tune a carb with a thermostat change? Sometimes the answer is yes..
@@flinch622 yes, longer hotter intake tract maybe needs larger droplets, short and cool, extremely high revving like F1 needs smaller droplets, thats why they have something like 100 bar fuel pressure and injector high outside intake trumpet.
Plug!Tune winter engine,step down few noozles in summer.Gasolin worst case scenario.Always smallest noozle,and screw farest back,untill peak other way.Sound great,but less torqe.Change equal plug heat number,another metal same logic.Burn more chamber,lesser fuel,50-60-70-80%.Any other way engine heats up,engine knocking,stalled.Oil,fire.Slow fuel pipes,small carburator,slow filter
Nice video. But was it a 850 or a 950 carb on the 350 and was it a 496 cu in or a 396 cu in the largest big block you built. Sorry to be confused but I am LOL. Thanks again for all you’ve contributed to the world of racing
Experts say that a spacer does not work as well on a divided intake as on An open one ! Well i had a 20 hp. Gain on the dyno with a 400 sbc. With an air gap intake ! I used a 2 inch 4 hole spacer but on the short plenum Side i ground out the divider compleatly so it looked like a oval race track The engine instantly sounded differently! I equalized the plenums !!
Excellent as always. What about some story about the ports ina pinto cyclinder head. Or swap the 2.0 pinto head for a smaller port 1.6 head. Thanks for ireland 🇮🇪
Spark plugs. 1962 Had Champion race plugs you described in an alcohol circle track engine. Ran really great. Track emergency, needed new plugs and only had a used set of conventional street plugs from a street engine. 😲 Put them in and gained a bunch. All I can figure is that the plug tip gap farther into the chamber was it. Heat color was good. 👍👍😎 Never bought another race plug. BTW. Next few years had tremendous trouble with Champions in ANY type vehicle. Never bought another champion either.
I had to watch this twice. I have two theories and they're probably both wrong. The first theory is was both blocks cylinders prepared the same? I came up with that from your previous video and book. The second theory is could there have been a hairline fracture near the bottom of the cylinder?
David, How about a video debunking flow vanes around intake valve guide stems in a port. Good/bad/right/wrong. Is it worth building vanes from epoxy ? Great video's Dave.
David, I have a theory on header length for a SBC. Left side head spark plugs fire in this order and crankshaft revolutions; #1-4 revs, #3-6 revs, #5-4 revs, #7-2 revs. Given these uneven firing times should the header lengths, using the theoretic scavenge optimum of 31” as the base line for the average of 4 revs; tube #1-31”, #3-23.25”, #5-31”, #7-62” for a 4 into 1 or tri-y collector. Am I on the right track?
I have a question Mr. David, regarding the 1050cfm carburetor on that 350, were the cam opening and closing events different between that engine and the others that caused the carburetor to be happy in one engine and un-happy in others ?
DV, I've learned so much from you and your books over the years! I'm always searching to learn more. Some things are very difficult to get info on, too much monkey see monkey do. Keep up the videos!
David on the Mini test in which you lost power, did you increase fuel pressure to obtain the finer droplet size or did you change the injectors? I've seen situations in which an increase in pressure actually _causes a decrease in fluid flow!_ It's possible you lost the power because the F/A mixture had actually been leaned out! Just a suggestion.
bobby - we had endless dyno time and the guy who designed f1engines and the guy that designed the injection system standing there ready to jump in and help. We did sweeps on everything imaginable!!!!
@@marvingvx1 I understand and don't mean to imply any fault on your part, I realize you have much more experience. The chance my first idea is the solution is slim I know but I can't help my mind dwelling on it and I do have solid knowledge of the physics and engine theory. I have only 1 more thought about it, do you think it's possible that since a larger fuel droplet size has less surface area but larger volume that the small difference in increased burn time was applying force on the pistons longer and thus farther down the stroke as compared to the more vaporized charge burning up earlier and is already past maximum pressure? Could that account for the increased the horsepower?
@@marvingvx1 Yes sir I know you're skills and reputation, I don't claim to have the definitive answer, just offering food for thought about your old power mystery!
David, was curious about what state you lived in,? I thought that you mentioned going to a dyno and you went up to Birmingham to use a dyno like you are in south Alabama. That is where I am from anyway and was just curious which you probably don't want to give out your location and I wouldn't blame ya. I could listen to you all day and just absorb the knowledge . Ive hit every button That would help you out. What website can I go to buy your stuff for sale? Do you have any engine parts that you are selling?
Graham, your name sounds very familiar - did I go to your wedding all those yeas ago? Spoke to Don last a couple of years ago. do you know how Mr. Brilliant is doing??
@@marvingvx1 hi David, hope you are all good. I had my car on Aldons Rollers in about 1997..... Fitment and Mapping Weber Alpha fuel injection. I remember Alan Goodwin and Roger was on the rolling road. I met you at NEC Autosport Show on Mountune's Stand and you told me a fix for poor ring seal. I then attended your Seminar in Swansea.... 2012 I think... And surprised you that I had used the... 'David Vizard' Oil Extreme Break in Lube. Yes.... 200 bhp X-Flow on Northampton Motorsport's Superflow Chassis Dyno.... The best X-Flow they have seen. Also.... Roy Millington's Son was well impressed with my Car.
Papaya enzymes, help us older gentlemen digest our dietary protein well. Keeps us up at our fighting weight. Excellent inspirations your videos Dave. Thank you.
Missing 20 HP is a big deal... When it comes to a small engine.. if I'm understanding him right... It was a small, low cylinder count... Let's say 200 horse.... 20 HP makes a difference Ok.. so 103.. give or take 20 HP.. that's a noticeable difference indeed
We have a friends mustang that runs on 42 degrees total timing (which I think is a bit high) but if you retard the timing back to 36 degrees total timing it detonates like crazy mystery.. WHY?
This might just be my favorite episode of PowerTec10!! The unexplained can be so frustrating..
I've found that out myself. If you have an idea you think will work, and then it turns out this idea "doesn't work," when you finally figure out why this idea "doesn't work," you still learn something in the process.
Thanks David, your knowledge is always appreciated!
I had a similar problem with a Pro16 car in 2002, 35 psi boost on a 2 liter Honda motor (ACT sponsored car for the 2002 NOPI nationals). It was making 300 HP at the wheel... and nothing made it better. Hours later they finally asked me to take a shot at tuning it, mostly because I was ready to shut down for the night. Quickly realized that something was wrong with the ignition system (insufficient amps to run it). Added a second battery, pulled, 400 WHP. 1 hour of tuning later, 620 WHP on a 2.0 liter Honda... which took the class at LACR that year (edit: it might have been 2nd place).
More eyes and brains on a problem never hurts. All too often we focus so closely we're blind to a different view.
Great catch!
Really... 300 to 600 aye... Interesting.
With the same engine.. same parts...
Huh... Sure
@@strydyrhellzrydyr1345 ya, same engine, same parts, same dyno session. Still have the signed photo from the team thanking me. I tell you what, track down Jojo Callos and ask him yourself. We were on the dyno way past midnight on Friday before the qualifiers.
A badly functioning ignition system will do exactly that much damage to your power. It was a Crane Hi-7 system which draws an inordinate amount of power and requires very specific wiring to operate correctly. It was also the first MOTEC system that I had tuned.
Doubt it all you want. I had failures too, like the time I calculated out (and built) what I thought was the perfect intake and exhaust system (promptly losing 50 HP) over baseline on a 13B rotary. Finally threw away the intake, and was able to pick up power, but I was humbled.
There were motors I couldn't find any power, but usually, if I was going to find a bunch of power - it was on the ignition side of the equation.
The 350 mystery....rocker type, and ratio? "Beehive", conical springs?
You stated that he ported the heads himself. Assuming you weren't standing there over his shoulder the entire time, maybe he milled them, as well. Enough to bump the compression ratio closer to 11:1.
You probably still have the spec sheet for the cam grind he ordered. Do those specs have room that would favor a half point more in compression?
What header tube diameter was that engine running?
There are some many tiny variables, that it's not surprising that the AD Dominator only ran perfectly on that particular build.
Anyway, I have to say that this was one of the most enjoyable videos that you've made here on your channel, Mr. Vizard. I could sit and listen to your stories for hours on end. Please consider making more in depth videos, recounting your past life experiences in racing, and the engines you built for those paricular races. These stories are NOT "boring!"
Sorry for the novel. But my Dad was a drag racer in San Antonio, TX., in the 1960s. And a great race engine builder in his own right. He's gone now, and I wish I had the presence of mind to document (video record), his stories behind the boxes of drag racing trophies I found after he passed away. So please, tell us all of yours.
With much respect. ❤
I would love to watch a 45 min break-down and review of this motor. Send a camera thru every port.
A mistake is a chance to learn something new. A success is just a confirmation of what you already knew. I think both have their place, but figuring out how to fix a mistake can be so much more rewarding!
Extremely well said Michael!!
I put new different brand sparkplugs in the 351W engine in my boat and it wouldn't start... put the old worn out sparkplugs back in and it started right up... looking closely at the new plugs, the steel body shell of the plug stuck out much further beyond the threads and was apparently shrouding the spark too much...
Had NHRA Stock Eliminator AMC AMX that wouldn’t respond to ANY tuning changes. Up this this point, tuning changes had always worked. Then as R&D made more HP, it hit a wall. Put significantly colder race plugs in and everything worked again. This was a record holding car.
well David i am going out on a limb here on the why the carb worked on that 350 engine ,,, the ported heads , the total seal rings, and the solid lifter cam ,,, made that carb think it was on a big block because it was moving enough air to work in the lower rpm range ,,, thats my thought in a nut shell ,,, David so glad you take the time to teach us what we dont no THANKS TONY
I have built many street engines in my life so far. Most ran pretty good. I ALWAYS learn something valuable watching your videos. Thank you for sharing so much of your knowledge and experience!
With regard to the Mini engine more fuel vapor in the intake charge results in less airflow. Air flows best without liquid in it. That engine where the Dominator worked well probably had excellent port velocity increasing the signal to the boosters.The chamber shape of that EQ head is very efficient with optimal swirl and power production. And the iron head harnesses more heat energy. Add in optimal quench clearance, your porting tricks and properly spec’d cam and you get more low end torque than those other engines where the Dominator didn’t work well.
On the spark plug dilemma, I have a 2-stroke dirt bike and I keep spare spark plugs handy. All of those plugs are different. There are AC Delco, Autolite, Champion, Motorcraft and NGK. All ARE properly match-spec'd for the bike. These spark plugs do NOT perform identically, and one stands out magnanimously over all others. I will always try different spark plugs in whatever engine because of this.
Being a motorcycle mechanic 'forever' the only theory I can come up with is for the Mini engine conventional vs 'race' plugs.
Probably explained by the way the fuel/air was flowing over the plug end, spark kernel and flame propagation.
In effect, the mixture wasn't getting into the spark gap properly so burn was delayed.with max cylinder pressure happening too far into piston travel.
That would show up on gas analyser as OK burn but wouldn't be producing power(possibly continuing to burn in exhaust manifold or pipe? did you check temperatures?)
I remember reading about something similar when surface discharge plugs for a Suzuki RE5 rotary were fitted to a conventional engine as an experiment due to conventional plugs overheating.
Shortening side electrode for a shorter heat path seemed to help (NGK made special short side electrode plugs for racing at one time, no idea if they still make them?)
Last NGK catalogue I saw them in was around 1979 when 'real' work got in the way of playing with engines
The music at the end for some reason(that I can’t explain) is very powerful emotionally. Excellent information as usual even if I am just a noob when it comes to engine building/performance
I always said "there's dog engines and freak engines"...Built two specifically the same and there's one dog and one freak...Yep seen it done it...Good stuff Dave.
I had that problem once. Once he weather changed, the horsepower went up. All about air density also.
I like how you said the Dyno supports your findings and not proves it. Great video Thank you for sharing some here knowledge I love mystery builds that you just can't explain makes you think.
The over-atomized fuel made less power because the fuel displaced the air in the intake, you want the fuel to vaporize just as the intake valve closes so it doesn't take up space in the intake charge.
Liquid fuel is much denser than vaporized fuel, having it be still a liquid in the intake charge increases volumetric efficiency.
Hello Mr. Vizard; I was hoping you could address a question I commented in your recent unequal length header video...
1.) Please assume an engine that produces peak horsepower @ 6500-RPM or less (if responding to Q#'s 2 & 3).
2.) Would you apply the (SAME +/- 4") primary lengths changes if the header were a 4-2-1 design vs. 4-1 design?
3.) Would a 4-2-1 header be superior to a 4-1 header given both had "ideal" / customized header primary lengths?
Any feedback you're willing to provide is GREATLY appreciated; keep up the good work!!! 👍
Regarding the Dominator only working down low on the one engine, my wild guess is that reversion pulses weren't striking the carburetor base as strongly on that one. Maybe something in the intake tract reduced reversion (or the pulses got somewhat cancelled by each other) or the carburetor was positioned a little higher (spacer or taller plenum?) Interesting stuff.
Definitely sounds like the right direction.
I tend to agree...
It's interesting to see the fuel fog cloud from reversion above the carb.s on a dual quads cross ram intake with too shallow plenums...
Found out in my young years that , sometimes a engine would actually run real well
And sometimes you put time and money into one and it just don’t do that well
The plug with the best flame travel made the best power.
A conventional spark plug with an "L" shaped electrode can shield a tiny volume of fuel/air mixture tightly around the spark allowing it to ignite better, causing a hotter more rapid flame travel and more complete combustion, leading to more power and better throttle response!
PS; as compared to an open electrode type racing spark plug.
@@logan_e Hence indexing shims.
@@logan_e you mean an "L" shaped ground strap. The electrode is in the middle and is the "jumping off" point of the spark. Common to get those mixed up.
@@joe-hp4nk I like it- what is your preference? do you index the ground strap towards the intake valve to create an "umbrella" for the incoming charge or index it the opposite way so that the spark is completely exposed and open to the charge coming from the intake valve?
@@kevinclancy. The latter, to me it's a no brainer.
Had a 440 dodge years ago, that would take as much fuel as you could give it and it wanted more.
What THE FLUKE!!... 😳
It must be aliens, or ghost, maybe both! They are working together!!
This is all mechanic / engineering gold. Thanks for sharing David.
David, also curious if you experimented with intake plenum Helmholtz resonators? I’d seen them on many passenger cars for noise attenuation, also the benefit of engine tuning.
On engine number one, you might have put a set of different dyno headers on that had some internal rust forming on the pipe interior surface. Smoky Unich told a story about how he lost a bunch of power by doing this !
Great episode DV, makes me feel good to know that even with all your dyno time and tuning experience there are some mysteries that we mortals cannot explain. There's sometimes just too much going on in there to explain it.
For the "droplet" problem... this shows up all the time in EFI applications. Some engines and manifold combos seem to favor relatively large droplets and others want relatively fine droplets. Might be that the wave action actually favors a certain droplet size, and it might also be that the smaller droplet sizes need a higher compression ratio to work as well. One is always messing with the actual, effective air density of the intake charge in some way when droplet sizes are messed with, and if the actual effective air density goes down, then the engine will want a higher compression to make the same or more power than the old set-up that had a higher density with a lower compression... this is exactly the reason why D.I. engines make a lot more power than the same engine with only port injection does with dry, light air all the way to the cylinder. They run a much higher compression to compensate for the lower density of the intake charge!
That reminds me of Gail Banks, built a super charged engine, with a good bit of boost, made exactly the same power as without boost! Haha all the heat and loss of efficiency,
Yeah sometimes you just don't know what little thing will throw a wrench into the worx! 🔧
#1 was hilarious. It reminded me of a story I read in a book of a particular class of steam locomotive where all members bar 1 performed to spec. The recalcitrant loco was the subject of much investigation and extensive modification none of which made the slightest difference.
There have been reports from firemen of identical steam locomotives that have different firing and operating characteristics even though the same coal was used. Some were easy to fire and others were difficult to fire yet had the same boilers and fire boxes. One of those odd things.🤨
Amazing information as always can’t wait for the 4 valve head stuff
Always a treat and always appreciated. Yes, I nailed the number 1 like again…
Worked on an engine program for an OEM where the last improvement/optimization caused the engine to lose all previous gains. The engine program was canceled at the cost of millions of dollars lost. Also worked on vibratory feeding systems. Sometimes in the tuning process a "high Q" combination could be achieved, after steady small increments were implemented, that suddenly out produced the previous iteration by a profoundly wide margin. Turn the system off, come back the next day, and the numbers went straight into the toilet.
Ambient atmospheric conditions can cause such effects, is it possible those were affecting your vibratory feeding system and had gone unnoticed?
@@logan_e One source of variation learned late was that the springs on the vibrators were made of fiberglass reinforced plastic which had a 'memory'. They literally changed their spring rate after sitting overnight!
@@donbrutcher4501 Interesting, that's a unique spring material I'm not familiar with, or more accurately have never worked with!
I Enjoy the channel David
Had a 451” Big Block Mopar Drag car. New engine. No dyno time. First pas went 10.70 @ 125 MPH. Friends were ecstatic. I was not. I just did not pull in high gear (a PG trans). I went up 2 jet sizes in the 4150 Holley. Next pass: 10.02 @ 132 MPH and pulled like a freight train! Most say BS. Just dramatizes being on the wrong side of lean jetting. Never hanged jets again.
A couple of entries for _The Journal of Unrepeatable Results._
Love it... you need to get your priorities right. Basically he's saying.
Racing takes precedent over marriage.
Life of experience many thanks
Wow! The hidden idiosyncratic variables!
Great episode David!! Thank you!!
Your the best at explaining the process of the work you do on these engines......were going to soulth carolina this weekend i wouldnt mind stopping by to shake your hand and say thank you in person.....any way thank you....im in the process of doing a 350 sbc bulid.......i will use the tips your passing out to us......
In the case of the student designed and built motor, you stated several head porters could not believe the flow numbers. Those 1050s flow what, 1000 CFM of air, or more? A lesser 350 could not handle the amount of air and fuel being thrown at it, so it spits some back out! I believe flow is the answer.
The cam is probably a factor, too.
Thanks David, that was fun.
For #2, the only thing that makes any sense at all is that the conventional type plug repositioned the start of the burn in a more favorable spot of the charge. We always assume that the charge at the point of combustion is going to homogenious enough to get all the power that can be had, but this is a simplification and can be wildly off from reality!! especially if this was a carbed forced induction engine... the fuel air ratios for individual cylinders can be all over the place but average out to give a good AFR reading at the tailpipe, and worse than that, the in cylinder AFR's and the point of combustion can be all over the place as well and still average out.
It is fun to play with sbc but running over the math there is just no way to beat an ls.
will somebody please buy Dave a lapel mic or something? i only get left channel sound and i have to turn my volume all the way up to hear him..
The right channel is only white noise. Best to copy the left channel to the right and use noise suppression software (
A thought on that mystery did you offset the grind on the rods throws to increase the stroke that could help with the Piston speed to increase your air volume down low on the rpm to make that large carb respond.
Is it possible that the slightly larger droplet size better absorbed heat without affecting the combustion process?
I would have never guessed you could loose half the engines power with just spark plugs without the thing exhibiting missfiring. Was it half power across the rev band or mostly at the hp peak? The dynamics of an engine are an insanely complex thing. Even 100 years after their invention accurate modeling of the entire engine is difficult to do. Sometimes things defy convention.
HI DAVID THIS VIDEO WAS SO GOOD I HAD TO WATCH IT AGAIN, THANK YOU
Thank you for your videos. It's was refreshingly different.
I wonder what the manifold vacuum was under the carb on the mystery 350 vs the ones it didn't like. I'm not a professional engine builder but thinking out loud I wonder if it wasn't a combination of cam timing and the plenum and entry to the ports in the intake being the perfect storm to make it work.
So much detailed attention is paid to the intake manifold, cylinder heads, and headers, seems like the one element of a NA engine that I think should be examined is the carburetor throats. The throats are close together and some models are built with sharp edges. Velocity stacks don't do much to remedy pulse interferences. Maybe some hp could be gained if the right individual stack design were developed.
Put a divider plate inside the velocity stack ?? I'm assuming this would be on a dual-plane set-up.
@@peterdarr383 To put it simplistically, yes. The detail that porting requires would be the same implemented to design a horn fitted over all throats.
Lol... I wonder if that guy is still married ..
If so I'm thinking he did have his priorities quite straight enough without his help... Lol.
Larger droplets & more power? I'd be thinking flame propagation slowed down a touch, and a few extra degrees of crank rotation were found close to peak cylinder pressure. Petrol does not burn until it finds air.
Exactly! You said it so much more simply than I did, lol I got a bit lost in the details but I agree!
Larger droplets have less surface area but more volume, that takes slightly longer to burn, keeping more pressure longer into the power stroke; more torque = more horsepower!
Phase reaction at the throat/seat .
Larger droplets doesnt vaporize before cylinder, you dont want vapor in the ports.
@@V8Lenny Vapor can be a complex matter to manage: a fluid is somewhere between between being all liquid and all gas. Finding the sweet spot for power or mileage usually don't coincide. Having the correct amount of heat in the engine can make a difference. Tune a carb with a thermostat change? Sometimes the answer is yes..
@@flinch622 yes, longer hotter intake tract maybe needs larger droplets, short and cool, extremely high revving like F1 needs smaller droplets, thats why they have something like 100 bar fuel pressure and injector high outside intake trumpet.
Plug!Tune winter engine,step down few noozles in summer.Gasolin worst case scenario.Always smallest noozle,and screw farest back,untill peak other way.Sound great,but less torqe.Change equal plug heat number,another metal same logic.Burn more chamber,lesser fuel,50-60-70-80%.Any other way engine heats up,engine knocking,stalled.Oil,fire.Slow fuel pipes,small carburator,slow filter
I'm guessing the 350 CID/Holley Dominator engine was a combination of headwork and camshaft tuning
Nice video. But was it a 850 or a 950 carb on the 350 and was it a 496 cu in or a 396 cu in the largest big block you built.
Sorry to be confused but I am LOL. Thanks again for all you’ve contributed to the world of racing
I believe the 1050 worked on that 350 was due better air flow. I'm curios to know how high you turned the little 350
to get peak HP ?
Experts say that a spacer does not work as well on a divided intake as on
An open one ! Well i had a 20 hp. Gain on the dyno with a 400 sbc. With an air gap intake ! I used a 2 inch 4 hole spacer but on the short plenum
Side i ground out the divider compleatly so it looked like a oval race track
The engine instantly sounded differently! I equalized the plenums !!
Excellent as always. What about some story about the ports ina pinto cyclinder head. Or swap the 2.0 pinto head for a smaller port 1.6 head. Thanks for ireland 🇮🇪
Spark plugs.
1962 Had Champion race plugs you described in an alcohol circle track engine. Ran really great. Track emergency, needed new plugs and only had a used set of conventional street plugs from a street engine. 😲 Put them in and gained a bunch. All I can figure is that the plug tip gap farther into the chamber was it. Heat color was good. 👍👍😎 Never bought another race plug.
BTW. Next few years had tremendous trouble with Champions in ANY type vehicle. Never bought another champion either.
The Truth is out there !
Thank you David , much appreciated
Racing is more important than marriage
Thanks again david!!
Enjoyed this Thank you !!!
Thanks!
I had to watch this twice. I have two theories and they're probably both wrong. The first theory is was both blocks cylinders prepared the same? I came up with that from your previous video and book. The second theory is could there have been a hairline fracture near the bottom of the cylinder?
David,
How about a video debunking flow vanes around intake valve guide stems in a port. Good/bad/right/wrong. Is it worth building vanes from epoxy ?
Great video's Dave.
All the best have failed their way to success
Profound words right there, -spot on.
That is exactly right!
DV; Thank you, v/r wh
David, I have a theory on header length for a SBC. Left side head spark plugs fire in this order and crankshaft revolutions; #1-4 revs, #3-6 revs, #5-4 revs, #7-2 revs. Given these uneven firing times should the header lengths, using the theoretic scavenge optimum of 31” as the base line for the average of 4 revs; tube #1-31”, #3-23.25”, #5-31”, #7-62” for a 4 into 1 or tri-y collector. Am I on the right track?
Of course I am using the "SWAG" Thierry. But thinking about the what air speeds are on the 350
Had to be his high IQ camshaft choice.
I have a question Mr. David, regarding the 1050cfm carburetor on that 350, were the cam opening and closing events different between that engine and the others that caused the carburetor to be happy in one engine and un-happy in others ?
Sometimes weird stuff happens. I once had a 6 cylinder that unwound number 5 plug every 3 weeks. Different brands or torque made no difference
Safety wire the spark-plug in place ?? JUST THE 1 !
Oversized threads
Thank you Sir!
Berry grant carbs are top notch as well
Would the mini with the webber and different cam timing have been super efficient
So 580 engine dyno is about 480 hp wheel depending on differential and transmission used. accessories can rob as wheel
Maybe 560 to hubs, rollers are difficult, small roller has very high rolling resistance but still never 100 hp loss.
My 500 SL Benz uses NGK plugs with 4 electrodes that come off the side of the positive electrode. $27.00 each.
1050 Dom's... Are what I hear ppl swear by
DV, I've learned so much from you and your books over the years! I'm always searching to learn more. Some things are very difficult to get info on, too much monkey see monkey do. Keep up the videos!
David on the Mini test in which you lost power, did you increase fuel pressure to obtain the finer droplet size or did you change the injectors?
I've seen situations in which an increase in pressure actually _causes a decrease in fluid flow!_ It's possible you lost the power because the F/A mixture had actually been leaned out!
Just a suggestion.
bobby - we had endless dyno time and the guy who designed f1engines and the guy that designed the injection system standing there ready to jump in and help. We did sweeps on everything imaginable!!!!
@@marvingvx1 I understand and don't mean to imply any fault on your part, I realize you have much more experience.
The chance my first idea is the solution is slim I know but I can't help my mind dwelling on it and I do have solid knowledge of the physics and engine theory.
I have only 1 more thought about it, do you think it's possible that since a larger fuel droplet size has less surface area but larger volume that the small difference in increased burn time was applying force on the pistons longer and thus farther down the stroke as compared to the more vaporized charge burning up earlier and is already past maximum pressure?
Could that account for the increased the horsepower?
@@marvingvx1 Yes sir I know you're skills and reputation, I don't claim to have the definitive answer, just offering food for thought about your old power mystery!
So what your saying is every single engine is like a person and reacts as such.
David, was curious about what state you lived in,? I thought that you mentioned going to a dyno and you went up to Birmingham to use a dyno like you are in south Alabama. That is where I am from anyway and was just curious which you probably don't want to give out your location and I wouldn't blame ya. I could listen to you all day and just absorb the knowledge . Ive hit every button That would help you out. What website can I go to buy your stuff for sale? Do you have any engine parts that you are selling?
Charlotte area
I'm guessing you we on Keith Dortons dyno?
Would that have been Aldon Automotive chassis Dyno in Brierley Hill, David?
Graham, your name sounds very familiar - did I go to your wedding all those yeas ago?
Spoke to Don last a couple of years ago. do you know how Mr. Brilliant is doing??
@@marvingvx1 hi David, hope you are all good.
I had my car on Aldons Rollers in about 1997..... Fitment and Mapping Weber Alpha fuel injection.
I remember Alan Goodwin and Roger was on the rolling road.
I met you at NEC Autosport Show on Mountune's Stand and you told me a fix for poor ring seal.
I then attended your Seminar in Swansea.... 2012 I think... And surprised you that I had used the... 'David Vizard' Oil Extreme Break in Lube.
Yes.... 200 bhp X-Flow on Northampton Motorsport's Superflow Chassis Dyno.... The best X-Flow they have seen.
Also.... Roy Millington's Son was well impressed with my Car.
On that mini engine with the one plugs did you index them David.
O.m.e the plugs.dont like spell check
Papaya enzymes, help us older gentlemen digest our dietary protein well. Keeps us up at our fighting weight.
Excellent inspirations your videos Dave. Thank you.
The Cam he used made the 1050 Work Signal to the Carb Had to be Better with his Cam AKA Vacuum!
Patrick, vacuum at an idle with the throttle closed. Non at open throttle.
Halo mnr David vizard.can I use a ad carb on a outonatic .I've got a elcamino with a 350/350 turbo box in it
And how much swirl
I have no sound...
do you know ben alameda
Missing 20 HP is a big deal... When it comes to a small engine.. if I'm understanding him right... It was a small, low cylinder count...
Let's say 200 horse.... 20 HP makes a difference
Ok.. so 103.. give or take 20 HP.. that's a noticeable difference indeed
We have a friends mustang that runs on 42 degrees total timing (which I think is a bit high) but if you retard the timing back to 36 degrees total timing it detonates like crazy mystery.. WHY?
That sounds like those old '66 289 peanut chamber heads like C6OE-m.
David is there a link or email address where i can contact you and or request a topic or discuss some questions i have for you?
Thanks!
Thanks!
Dave - awesome thanks!!!