Holley “Base” Power Valve selection procedures. * Automatic transmission: Engine at operating temperature, measure engine vacuum in gear idling with brake applied. PV = observed vacuum reading minus 2hg. Example: 8.5 - 2.0= 6.5 *Manual transmission, engine at operating temperature with stable curb idle. Measure idle vacuum and Divide by 2. Example 13.0/ 2= 6.5 PV As a general tip, if you’re in between sizes try the lower rated PV first. If you have very low engine vacuum in gear, under 4-5hg in gear you can try a 2.5hg PV but may end up needing to use a PV block off requiring increased main jet sizing +6-8. This is the Base method, it may work great as is but using a wideband to verify the AFR’s is the Pro tip and most accurate! 👍
But if you block up the pv for the primaries, and jet it up like 6 numbers, you are not going to get instant fuel (after the pump shot), till the engine goes up in rpms, and starts producing a decent fuel signal, to draw in from the primary jets = leaner. I think that what you probably do, but didn't mention, is maybe go with the bigger 50cc pump instead of the 30cc and mess with nozzles and cams to make up for that lean-ness you induced by blocking up the pv? Correct me if I'm wrong. I want to learn.
It's funny, I've gone back and fourth with guys on holleys half idle vacuum sequence for closing powervalves. The best way I've found is to block the valve off, go for a drive, see at what vacuum reading it start to get a lean spot, throw a valve in a couple numbers before that lean spot. Idle vacuum will definitely not tell you what you need at cruising and acceleration state.
I have a vaccuum gauge and wide band, side by side. And it helps a ton when tuning for power valve size. Holleys method said I needed a 3.5 The vacuum and wide band said I needed 8.5. My engine is definitely happier with 8.5 in it
My wideband just came in the mail and I can’t wait to start tuning. I’ve never had a good understanding of how well you can tune a carburetor. Now that Ive found your channel that’s all going to change.
Thanks for a fantastic tutorial about tuning power valves to your engine. I have used vacuum gauges to tune but my ears have given me better success at tuning. To me, it was very audible that your engine wasn’t happy with the 8.5 valve and was sweeter with the lower numbered valve. And, that little truck is a beast!!
I've got an 83' Ranger 4x4 with a stock 2.3L inline 4 and I just did a Holley 350 2 Barrel swap. I've been fighting a bad bog and hesitation when I use more than half throttle and it always happens at 2-2.5k RPM. Once it passes 3k RPM, she sings and runs pretty good. Switched out the pump cam from orange to black and it helped quite a bit. It seems the less fuel I have, the less it bogs and hesitates. I checked my power valve and I had a 8.5 in and swapped it out for a 5.5. Also switched to a 30cc pump while at it. Haven't tested it yet because I somehow snapped a fuel bowl bolt so I'm waiting on a new set to come in and a .025 anti pullover squirter for the accelerator pump. I do plan on getting an AFR gauge installed at some point. But this video made me understand PVs a lot better. Also proved my intuition correct and going with a lower number without doing much research.
Good information in this video, neat to see actual driving data and what making changes actually do. I have run a few different carburetors on one vehicle, two of them 600 cfm and one 450 cfm. All 3 were tuned to run approx the same AFR at idle, transition and cruise. However, one of them the AFR would go from 14-14.5 down to 10.5-11.5 depending on load when the power valve was open, the other would stay in the 12.5-13 AFR range when power valve was open. The difference not only did the richer PV circuit carb have doggy performance it also got about 1-2 MPG worse doing the same exact runs/commute than the carb that had the leaner PV circuit. Very important to get that circuit tuned right!
I agree with this video. Nice metering blocks like the lowered pvcr locations. Finding a decent average tune that works year round can be a challenge. I find nowadays i get by with just shoving a fbo bushing in the msd dist on my pump gas street motors and running the right heat range plugs
The first step is to set the carb to its original configuration, jet size, power valve, squirter size. Second step is to make the preliminary adjustments, fuel pressure, float, accelerator pump, idle mixture, secondary trottel, timing. Only then, can you start testing.
Great video ! You're a good teacher,this will be a problem solver for many out there.I'm 67 yo ,bracket racer for quite a while and can assure you 90% of the racers had no clue about correct pv selection.Got a couple questions.What pv restriction jet size was in the metering block to begin with and size did you drill it out to ? What size primary jets came in the carb ,what size was in it before you went down 10 sizes ? I've tried several different formulas including the one given by HeadFlowInc in the comments ,but still find myself reverting to the one I was taught over 50 years ago ;operating temp,in gear idling, read vacuum , divide by 2=pv size. Tune from there.
I have no idea what it was before I drilled them out. I just eyeballed a 1/16 drill bit and said that looks about right. 😆 I have a bag of .025s so if it was a bad idea I could adjust. It was a stock 950 brawler carb. Here is my original video when I went through it
You obviously got a race motor under the hood and I wonder if it's slowed you down dropping six sizes of jets I bet it did.. and all you had to do was change the discharge nozzle for your accelerator pump instead of all that work you just did for the power valve and now you just lost a quarter mile time by dropping your jets when you could have just dropped your discharge nozzle
@@rono3045 ha ha. You would know...... This guy has 2 gauges, side by side in the video. They tell the story, not you. Cruising down the highway steady, you should probably be around 14.5 to 15 afr, for economy. At max wide open throttle, the air fuel ratio should Start going towards 12.5 afr pretty quickly I would imagine. Then as you slowly let of the throttle, and reduce the load, it should slowly go back to around 14.5 to 15 afr. And I'm sure that his engine does that, or at least how he thinks the numbers should be. His engine screams! Great video.
It’s mind blowing that the 8.5 didn’t shoot that sucker lean asf ! But did the opposite Very interesting indeed !!! I know for my blow through carb my buddy opened up the power valve holes in the metering plate pretty much is the main thing to do when you want to do a blow through unit Love the tuning tricks brother!!
Hello I can help, you need to measure your manifold vacuum in kpa as it represents engine load better. Idle mixture screws are for idle and very low throttle them main jets are for the Cruze range and the power valve is for wot . The air bleeds will adjust the overlap aka when each circuit comes in . Your secondary throttle plates need to be timed first based on maintaining the highest kpa for a given rpm. You won’t get your mechanical secondary carb to run like a vacuum secondary on the street. Study the relationship of throttle position vs kpa aka throttle mapping no more throttle angle needed past highest kpa reading . Your getting lost in your tune because the secondary plate timings off .
I've got a few questions. What wide band gauge and O2 sensor are you using, where did you find your radiator and engine mounts? Man I love the 400. I'm doing a very mild Dart 427.
Hey thanks for making this video, very helpful. I seem to have the same issue with my PVCR. My carb is a 650 race demon and came factory with .059 sized restriction holes on the power valve channel. Just curious how many steps up you went in drill numbers? I think the next one for me from .059 is .063? FYI its a small displacement big cam big head motor so not much vacuum at idle (around 9hg @950rpm.) I am currently running a 4.5 PV. Thanks!!!!!
This is an amazing video! I’m having the opposite problem that you were when you were running that 8.5 PV. I’m running a 5.5 and at light throttle AFR is in the low 14s. But, when I let off it runs in the high 11s low 12s. I can’t seem to lean out my idle/transition AFR level. Will PV affect this? Thanks!
You need to rid of that POS fuel filter before your carb.Why ot just take a vacuum reading at crusing speeds? then select the the power valve at just below that range?
Let’s say you buy a used 750DP (pick any carb size) used and are going to fit it to a Street Strip SBC. How do you go about selecting a starting point with jetting/squirted nozzles etc for the initial start up?
New to carb tuning and would definitely appreciate any advice. I have a 306 sbf, mild cam with stock crank and rods. The carb runs at 11.5 or so at idle and gets rich at wot, around upper 9 to 10.2/10.5 on the afr gauge. 68 primary jets, 76 secondary with a 6.5 power valve. The idle mixer screws are at 1 1/2 turn out. At running temperature it has 7to8lbs of vacuum. Holley techs have me so confused with all this and would really appreciate any advice on where to go from here. Also the carb is a 600 cfm with electric choke and mechanical secondaries. Thanks again for any advice
I've been fooling with my truck all summer trying to get it to run right changinh power valves and jets I don't have the patience like you I'm getting ready to switch up to EFI ... I don't know which one I'm going to buy yet
Hi Mate , I have a 408 clevo and alloy heads and similar cam to you . I noticed u run a 4.5 power valve . But what jets are you running in the primary and secondaries? Would be great to point me in the right direction? I’m running 12.5 at cruise at 2500 . Way too rich . Thanks in advance!
given a standard Holley power valve are only set to close under vaccume Conditions Are there any cases where a blow through carb with a standard power valve will close under boost? My thinking is that the standard power valve will remain open under boost under you back off the throttle.. in only running 5 psi so thinking the brpv is not for me..? Thanks for any thoughts
The boost power valve is for positive pressure so it opens differently from the opposite side of the metering block. The conventional power valve is for draw through only boost with close that PV. Also the vacuum port for a draw through carburetors power valve needs to be blocked off in the front and back.
Thanks for your reply. So what you're saying is the additional pressure acting on the bowl side of the conventional power valve presses the standard power valve closed stopping fuel flow under some boosted conditions? I'm thinking about putting in a secondary brpv and having a conventional pv in my primary metering block and seeing if this combination will get me good afrs through the whole power band.@@TPVPRO
i have a problem on my 331 stroker with comp cams 290/290 cam woth 230/230on 50 when light throtlle cruising i get 14to 14.5 afr when i put the pedal slightly more down i get a stumble and i can play the throtlle to 16.5 afr when i do half throtlle i get 13.5 full throtlle is 11.5 (just started with the afr gauge tuning) what do you think is wrong? also if i get under 1700 rpm this light throtlle is more lean then when i'm cruising 2500 rpm on the other hand steady cruising at 1700 and 2500 rpm is around 14.5 afr
Could be a number of things I would check to see if all 4 idle air screws are open the same amount. If the idle is set low and the front and rear blades are almost closed it can do that also.
I'm running a qf 850 q series and I pulled plugs 5 and 8 looked perfect Pulled plugs 1 2 3 4.. they were Shiney wet?.. is that a ignition issue..msd 6aL.. Sbf 408w.. My cam is .300 .300 at 50..614 lift
You should always try to square your jets as much as possible. This video goes over that process extensively. czcams.com/video/SPRQHG-iaVg/video.htmlsi=dVqCIran7DhaA3gK
@@TPVPRO the jets yeah I see that because I bet there probably the same size as other restrictors that are in dominators and other high end billet metering blocks for low speed air bleeds idle circuits ECT....but the channel in question is the emulsion channels 👍
I think I had it an 8 split before and the WOT AFR was good. I then enlarged the power valve restrictions to .062. I had to drop the front by 6 to get the AFR back to where it was before. “So about a 14 split now front to rear.
@@TPVPRO awesome! Good enough! Gonna have to give a shot. Still tryin to dial in idle air fuel. Motor likes to idle a little on the rich side. Hi 11s to low 12's AFR. If i try anf lean it out anymore motor doesnt seem happy. Idle will sometimes slightly hang after blipping the throttle. Slower to return to an idle. Then motor temp will idle alot hotter. Cruise AFR is in the low 12.s i also have same problem. Once i start to tip in the throttle from a stoplight it will go instant rich into the 10s. Any slight acceleration motor just goes way rich. Other then that WOT is on target. Car still hot starts perfect. Even with the richer mixture. Sorry for such long comment! Hahah
@@1969pontiac406 great comment. So your leaner idle mixture has a direct effect on the engine revving back down to idle??? I kinda have that problem I think. I like my 383 to rev up fast and come back down to idle even faster! Lol. I know my 381 stroker isn't going to perform magic like an F1 racer!
You don’t jet the mains for cruise, you are coming at this completely wrong! The first thing you do is find out what timing your motor likes at idle.. Big cams need 20-30 degrees, if u have a small cam maybe 13-17. That’s where u start! Then once u have the correct timing, you start on butterfly and transition slot adjustments , you don’t want to expose too much slot, or it will idle rich. Expose only 1/16 of the slot. Then if your 4 corner idle adjustments don’t change idle quality, change either idle feed restrictors or idle air bleeds,, once the needles adjust the idle feed u set for highest vac on port vacuum. Then check with a AFR gauge to see where your AFR is at at idle.. If it’s 13-14 your good, if not,, adjust according with air bleeds for min change or idle feed for a lot. Next adjustment will be Transition adjustment, from idle to cruise, this is checked with AFR gauge, at cruise u want 14-16.. adjust restrictors in meter block for transition feed. Next you adjust main jets for full throttle and high speed bleeds, 12 to 12.5 AFR is usually good,, Now if you have a power valve in the primary, block it, and only run in the secondary,, Find out what vac u have at cruise and go up 1-2 points on vac and Bam.. that’s how u approach adjusting a carb! If you have a hesitation, then either your timing curve is wrong, or your AFR is out of wack…
This video was only on how the power valve works and how it affects AFR not a complete tuning video. I have other videos in my Holley 4150 playlist for that. I run a locked out distributor you don't need a timing curve with a stall that flashes at 5000rpm. Plus you never talked about the accelerator pumps and they are extremely important.
Holley “Base” Power Valve selection procedures.
* Automatic transmission:
Engine at operating temperature, measure engine vacuum in gear idling with brake applied. PV = observed vacuum reading minus 2hg.
Example: 8.5 - 2.0= 6.5
*Manual transmission, engine at operating temperature with stable curb idle. Measure idle vacuum and Divide by 2.
Example 13.0/ 2= 6.5 PV
As a general tip, if you’re in between sizes try the lower rated PV first.
If you have very low engine vacuum in gear, under 4-5hg in gear you can try a 2.5hg PV but may end up needing to use a PV block off requiring increased main jet sizing +6-8.
This is the Base method, it may work great as is but using a wideband to verify the AFR’s is the Pro tip and most accurate! 👍
My thinking is this might be the method for a baseline start, then adjust from there.
But if you block up the pv for the primaries, and jet it up like 6 numbers, you are not going to get instant fuel (after the pump shot), till the engine goes up in rpms, and starts producing a decent fuel signal, to draw in from the primary jets = leaner.
I think that what you probably do, but didn't mention, is maybe go with the bigger 50cc pump instead of the 30cc and mess with nozzles and cams to make up for that lean-ness you induced by blocking up the pv?
Correct me if I'm wrong. I want to learn.
It's funny, I've gone back and fourth with guys on holleys half idle vacuum sequence for closing powervalves. The best way I've found is to block the valve off, go for a drive, see at what vacuum reading it start to get a lean spot, throw a valve in a couple numbers before that lean spot.
Idle vacuum will definitely not tell you what you need at cruising and acceleration state.
I have a vaccuum gauge and wide band, side by side. And it helps a ton when tuning for power valve size. Holleys method said I needed a 3.5
The vacuum and wide band said I needed 8.5. My engine is definitely happier with 8.5 in it
My wideband just came in the mail and I can’t wait to start tuning. I’ve never had a good understanding of how well you can tune a carburetor. Now that Ive found your channel that’s all going to change.
Power valves make such a difference.
Thanks for a fantastic tutorial about tuning power valves to your engine. I have used vacuum gauges to tune but my ears have given me better success at tuning. To me, it was very audible that your engine wasn’t happy with the 8.5 valve and was sweeter with the lower numbered valve. And, that little truck is a beast!!
I’ve seen a ton of power valve videos and yours is the best so far.
I keep starring at the free standing sparkplug
I've got an 83' Ranger 4x4 with a stock 2.3L inline 4 and I just did a Holley 350 2 Barrel swap. I've been fighting a bad bog and hesitation when I use more than half throttle and it always happens at 2-2.5k RPM. Once it passes 3k RPM, she sings and runs pretty good.
Switched out the pump cam from orange to black and it helped quite a bit. It seems the less fuel I have, the less it bogs and hesitates. I checked my power valve and I had a 8.5 in and swapped it out for a 5.5. Also switched to a 30cc pump while at it. Haven't tested it yet because I somehow snapped a fuel bowl bolt so I'm waiting on a new set to come in and a .025 anti pullover squirter for the accelerator pump. I do plan on getting an AFR gauge installed at some point. But this video made me understand PVs a lot better. Also proved my intuition correct and going with a lower number without doing much research.
Good information in this video, neat to see actual driving data and what making changes actually do. I have run a few different carburetors on one vehicle, two of them 600 cfm and one 450 cfm. All 3 were tuned to run approx the same AFR at idle, transition and cruise. However, one of them the AFR would go from 14-14.5 down to 10.5-11.5 depending on load when the power valve was open, the other would stay in the 12.5-13 AFR range when power valve was open. The difference not only did the richer PV circuit carb have doggy performance it also got about 1-2 MPG worse doing the same exact runs/commute than the carb that had the leaner PV circuit. Very important to get that circuit tuned right!
Tylers tuning tips RULE!!!!!
I just love your videos 👏 U always showing us how to something very interesting!!
The more I learn about holley carburetors the more I appreciate edelbrock carburetors, but I will continue to learn about holleys.
I agree with this video. Nice metering blocks like the lowered pvcr locations. Finding a decent average tune that works year round can be a challenge. I find nowadays i get by with just shoving a fbo bushing in the msd dist on my pump gas street motors and running the right heat range plugs
thank you this is what i have been looking for a driving example of what to expect .
Best explanation and demo ever 👍
Perfect explanation. Drilling out metering block is exactly what you do, how explained it smaller jets for milage. Hardly anyone knows this.
Thanks for sharing your knowledge!
Looks like a blast to drive keep the videos coming
The first step is to set the carb to its original configuration, jet size, power valve, squirter size. Second step is to make the preliminary adjustments, fuel pressure, float, accelerator pump, idle mixture, secondary trottel, timing. Only then, can you start testing.
Dude, she is sounding healthy!!
I loved how he let out for a sec then dented the floor pan the next punch. That mutha was talking to him!
Great video !!!! Now let’s go gap some turbos !!!!!!
They better be some slow turbos 😆
@@TPVPRO Nitrous. Lots of Nitrous !!!!!!!
Great video ! You're a good teacher,this will be a problem solver for many out there.I'm 67 yo ,bracket racer for quite a while and can assure you 90% of the racers had no clue about correct pv selection.Got a couple questions.What pv restriction jet size was in the metering block to begin with and size did you drill it out to ? What size primary jets came in the carb ,what size was in it before you went down 10 sizes ? I've tried several different formulas including the one given by HeadFlowInc in the comments ,but still find myself reverting to the one I was taught over 50 years ago ;operating temp,in gear idling, read vacuum , divide by 2=pv size. Tune from there.
I have no idea what it was before I drilled them out. I just eyeballed a 1/16 drill bit and said that looks about right. 😆 I have a bag of .025s so if it was a bad idea I could adjust. It was a stock 950 brawler carb. Here is my original video when I went through it
czcams.com/video/RFJPhaFqAA8/video.html
@@TPVPRO Thanks
You obviously got a race motor under the hood and I wonder if it's slowed you down dropping six sizes of jets I bet it did.. and all you had to do was change the discharge nozzle for your accelerator pump instead of all that work you just did for the power valve and now you just lost a quarter mile time by dropping your jets when you could have just dropped your discharge nozzle
@@rono3045 ha ha. You would know......
This guy has 2 gauges, side by side in the video.
They tell the story, not you.
Cruising down the highway steady, you should probably be around 14.5 to 15 afr, for economy.
At max wide open throttle, the air fuel ratio should Start going towards 12.5 afr pretty quickly I would imagine.
Then as you slowly let of the throttle, and reduce the load, it should slowly go back to around 14.5 to 15 afr.
And I'm sure that his engine does that, or at least how he thinks the numbers should be.
His engine screams!
Great video.
It’s mind blowing that the 8.5 didn’t shoot that sucker lean asf ! But did the opposite
Very interesting indeed !!!
I know for my blow through carb my buddy opened up the power valve holes in the metering plate pretty much is the main thing to do when you want to do a blow through unit
Love the tuning tricks brother!!
Still so much I want to learn for sure.
With that cam he probably only has 10 in of vac, wouldnt take much for the PV to open at 8.5. why would you think that would make it lean?
@@cuzz63 Yes it would make it FAT supplying enrichment immediately off idle.
@@TPVPRO thats what thought, wasnt sure what boosted cutlass was thinking
@@cuzz63 Boosted my boy, he has been a long time subscriber. His car is pretty sweet too.💪
Hello I can help, you need to measure your manifold vacuum in kpa as it represents engine load better. Idle mixture screws are for idle and very low throttle them main jets are for the Cruze range and the power valve is for wot . The air bleeds will adjust the overlap aka when each circuit comes in . Your secondary throttle plates need to be timed first based on maintaining the highest kpa for a given rpm. You won’t get your mechanical secondary carb to run like a vacuum secondary on the street. Study the relationship of throttle position vs kpa aka throttle mapping no more throttle angle needed past highest kpa reading . Your getting lost in your tune because the secondary plate timings off .
Good video my brother
I've got a few questions. What wide band gauge and O2 sensor are you using, where did you find your radiator and engine mounts? Man I love the 400. I'm doing a very mild Dart 427.
good video my brother
Just finding your channel, I’m building a second gen s10 pretty similar with a 406 sbc.
Hey thanks for making this video, very helpful. I seem to have the same issue with my PVCR. My carb is a 650 race demon and came factory with .059 sized restriction holes on the power valve channel. Just curious how many steps up you went in drill numbers? I think the next one for me from .059 is .063? FYI its a small displacement big cam big head motor so not much vacuum at idle (around 9hg @950rpm.) I am currently running a 4.5 PV. Thanks!!!!!
This is an amazing video! I’m having the opposite problem that you were when you were running that 8.5 PV. I’m running a 5.5 and at light throttle AFR is in the low 14s. But, when I let off it runs in the high 11s low 12s. I can’t seem to lean out my idle/transition AFR level. Will PV affect this? Thanks!
awesome!
This is also a good video. czcams.com/video/2bhVWTqNx8c/video.htmlsi=fdFGagGq7249nmYR
YEAHHHHHHHHHHH!!!
You need to rid of that POS fuel filter before your carb.Why ot just take a vacuum reading at crusing speeds? then select the the power valve at just below that range?
Easy Cathy...🐱
You said the lower power valve comes in later than the higher numbered power valve. I don't get that. Is there not more vacuum at higher RPMs???
Let’s say you buy a used 750DP (pick any carb size) used and are going to fit it to a Street Strip SBC. How do you go about selecting a starting point with jetting/squirted nozzles etc for the initial start up?
New to carb tuning and would definitely appreciate any advice. I have a 306 sbf, mild cam with stock crank and rods. The carb runs at 11.5 or so at idle and gets rich at wot, around upper 9 to 10.2/10.5 on the afr gauge. 68 primary jets, 76 secondary with a 6.5 power valve. The idle mixer screws are at 1 1/2 turn out. At running temperature it has 7to8lbs of vacuum. Holley techs have me so confused with all this and would really appreciate any advice on where to go from here. Also the carb is a 600 cfm with electric choke and mechanical secondaries. Thanks again for any advice
I've been fooling with my truck all summer trying to get it to run right changinh power valves and jets I don't have the patience like you I'm getting ready to switch up to EFI ... I don't know which one I'm going to buy yet
I am going to make another video in a couple of weeks that will prove useful, don't give up yet.
TY
That's what the TPV means tuning power valves. Lol
🤣🤣🤣👍
Hi Mate , I have a 408 clevo and alloy heads and similar cam to you . I noticed u run a 4.5 power valve . But what jets are you running in the primary and secondaries? Would be great to point me in the right direction? I’m running 12.5 at cruise at 2500 . Way too rich . Thanks in advance!
given a standard Holley power valve are only set to close under vaccume Conditions Are there any cases where a blow through carb with a standard power valve will close under boost? My thinking is that the standard power valve will remain open under boost under you back off the throttle.. in only running 5 psi so thinking the brpv is not for me..? Thanks for any thoughts
The boost power valve is for positive pressure so it opens differently from the opposite side of the metering block. The conventional power valve is for draw through only boost with close that PV. Also the vacuum port for a draw through carburetors power valve needs to be blocked off in the front and back.
Thanks for your reply. So what you're saying is the additional pressure acting on the bowl side of the conventional power valve presses the standard power valve closed stopping fuel flow under some boosted conditions?
I'm thinking about putting in a secondary brpv and having a conventional pv in my primary metering block and seeing if this combination will get me good afrs through the whole power band.@@TPVPRO
I don't have enough experience with blow through carbs to say yea or no. I only understand how they work. @@harmankardon478
Sweet nice tips
Great video....what is the make of your air fuel gauge?
i have a problem on my 331 stroker with comp cams 290/290 cam woth 230/230on 50 when light throtlle cruising i get 14to 14.5 afr when i put the pedal slightly more down i get a stumble and i can play the throtlle to 16.5 afr when i do half throtlle i get 13.5 full throtlle is 11.5 (just started with the afr gauge tuning) what do you think is wrong?
also if i get under 1700 rpm this light throtlle is more lean then when i'm cruising 2500 rpm
on the other hand steady cruising at 1700 and 2500 rpm is around 14.5 afr
All the tuning tips are great, we try to tune vacuum through the traps at WOT do you do that too?
I don't even have a port for vacuum on my current setup. I just read plus and AFR after a pass.
Would you recommend, disconnecting the secondaries while you tune the primaries and power valve?
No
My afr goes way lean if i let completely off the throttle and let it coast, what could that be a sign of?
Could be a number of things I would check to see if all 4 idle air screws are open the same amount. If the idle is set low and the front and rear blades are almost closed it can do that also.
I'm running a qf 850 q series and I pulled plugs 5 and 8 looked perfect
Pulled plugs 1 2 3 4.. they were Shiney wet?.. is that a ignition issue..msd 6aL..
Sbf 408w..
My cam is .300 .300 at 50..614 lift
Hard to say without seeing it in person.
when you changing the power valve do you have to change the jets at the same time
You should always try to square your jets as much as possible. This video goes over that process extensively. czcams.com/video/SPRQHG-iaVg/video.htmlsi=dVqCIran7DhaA3gK
Install a vac gauge as well.
What rear end gears do you have in that vehicle?
Emulsification jets
I have seen places give them different names for identification. I got a bag of .025s with a label "screw-in restrictions"
@@TPVPRO the jets yeah I see that because I bet there probably the same size as other restrictors that are in dominators and other high end billet metering blocks for low speed air bleeds idle circuits ECT....but the channel in question is the emulsion channels 👍
What would be the reasoning behind a power valve block off plug? Rebuilding a carb and its in there
It will just run a whole lot fatter during cruise without one in the front because you have to jet it up to compensate.
@@TPVPRO makes sense, the jets were crazy high!
Thanks for the reply
@@josephfriedrich9792 No problem brother
When your testing do you back the accelerator pumps off?
No you kinda need to have everything else set up very close before you tune the PV.
I'm curious, what metering block is he using ?
Stock Holley brawler blocks
Which wide band do you use?
What kinda jet split did you end up with after drilling out power valve circuit?
I think I had it an 8 split before and the WOT AFR was good. I then enlarged the power valve restrictions to .062. I had to drop the front by 6 to get the AFR back to where it was before. “So about a 14 split now front to rear.
@@TPVPRO awesome! Good enough! Gonna have to give a shot. Still tryin to dial in idle air fuel. Motor likes to idle a little on the rich side. Hi 11s to low 12's AFR. If i try anf lean it out anymore motor doesnt seem happy. Idle will sometimes slightly hang after blipping the throttle. Slower to return to an idle. Then motor temp will idle alot hotter. Cruise AFR is in the low 12.s i also have same problem. Once i start to tip in the throttle from a stoplight it will go instant rich into the 10s. Any slight acceleration motor just goes way rich. Other then that WOT is on target. Car still hot starts perfect. Even with the richer mixture. Sorry for such long comment! Hahah
@@1969pontiac406 great comment.
So your leaner idle mixture has a direct effect on the engine revving back down to idle???
I kinda have that problem I think.
I like my 383 to rev up fast and come back down to idle even faster! Lol.
I know my 381 stroker isn't going to perform magic like an F1 racer!
Doe engine temperature change when you run it leaner
Not as long as it's a light load on the motor.
Are you located in Georgia
Can I get my 232 I-6 Jeep to sound like your car?
😁
What kind of afr are you looking for on spray?
Like 11.5-11.8 but plugs will tell you the best story.
I feel like I’ve been watching this video forever and ya still haven’t gotten to the point 6 mins in…
Sorry for providing detailed information. 😥
You don’t jet the mains for cruise, you are coming at this completely wrong! The first thing you do is find out what timing your motor likes at idle.. Big cams need 20-30 degrees, if u have a small cam maybe 13-17. That’s where u start! Then once u have the correct timing, you start on butterfly and transition slot adjustments , you don’t want to expose too much slot, or it will idle rich. Expose only 1/16 of the slot. Then if your 4 corner idle adjustments don’t change idle quality, change either idle feed restrictors or idle air bleeds,, once the needles adjust the idle feed u set for highest vac on port vacuum. Then check with a AFR gauge to see where your AFR is at at idle.. If it’s 13-14 your good, if not,, adjust according with air bleeds for min change or idle feed for a lot. Next adjustment will be Transition adjustment, from idle to cruise, this is checked with AFR gauge, at cruise u want 14-16.. adjust restrictors in meter block for transition feed. Next you adjust main jets for full throttle and high speed bleeds, 12 to 12.5 AFR is usually good,, Now if you have a power valve in the primary, block it, and only run in the secondary,, Find out what vac u have at cruise and go up 1-2 points on vac and Bam.. that’s how u approach adjusting a carb! If you have a hesitation, then either your timing curve is wrong, or your AFR is out of wack…
This video was only on how the power valve works and how it affects AFR not a complete tuning video. I have other videos in my Holley 4150 playlist for that. I run a locked out distributor you don't need a timing curve with a stall that flashes at 5000rpm. Plus you never talked about the accelerator pumps and they are extremely important.
czcams.com/play/PLvY-OTrBnLAvf39HS4aVMdJS9KLLhDAyc.html
the info in this video seems exactly backwards to me.if you're too rich, you need a higher number power valve.
A higher number power valve opens sooner, at a higher vacuum. That makes it rich.