Probably worth noting, adjusting the pump cam arm play is a good cure for the stumble issue, provided the carb has already been tuned to the engine, and has previously run well. But if this is a different (new) carb, being used on an engine for the first time, it may not be the accelerator pump that is causing the bog. It could also be too big of a pump nozzle size for the engine. I had a similar issue when I installed a 450 Holley on a stock 305 GM engine. After tuning the air screws to obtain good vacuum, and having set float height, curb idle, pump cam preload, ect, I still had a stumble. The Holley pump nozzle was a size 31, and it would bog/hesitate right off idle. This was due to to much fuel being pumped in by the accelerator pump. Changing to a size 25 pump nozzle completely took care of the issue. Just thought this was worth mentioning. Great videos!
Been watching summit videos and all sorts of others couldn't get what they were talking about...+++ very informative you thoroughly explain and illustrate everything perfectly.keep making videos you are a good teacher!
Very helpful , Thanks , I'd like to spend a couple hours with you learning more about carb's . Some people are easy to understand and some are too technical . I can understand you . Once again ... Thank's .
One of the easiest ways to determine your accelerator pump setup is to just warm it up and push down on the pump adjustment nut and feed it a shot of fuel. If it bogs shorten the spring, if it likes it expand it
I think its more the shooter size that affects fuel delay, the bigger it is the faster the spring can recover, but the important thing is how well the engine responds. Shooter size is a good place to tune if engine still doesnt respond as it should
Thanks for your comments, my goal is to minimize crankcase pressure during high rpm racing conditions which makes more power that way and is safer for seals and gaskets, during wide open throttle the engine makes almost zero vacuum so a small diameter PVC hose will do very little in that regards so I don't bother with it, I use a large capacity breather instead
yeah the double pumpers are cool and the fact that it has an extra accelerator pump for the back is what make them cool. I'm at the point where im going to start messing with those fancy ones like you have though. at the moment I still run a normal holley 800 double pumper
Thanks for the response from what you said I'm having a rich issue which is what I was leaning towards because I have friends tell me all the time that they can smell the gas when I pass them. I guess the next thing on y list to buy is a jet kit and a accelerator pump cam kit along with the vacuum secondary spring kit because my secondaries aren't opening all the way either.
OH if a Holley was only that easy. Pump cam and nozzle size combo can be the biggest challenge you ever faced. Also, the transfer circuit comes in to play. If the butterfly are too far open, or not open enough. How rich or lean is the transfer. Maybe the bog is a lean transfer and your covering it up with accel. pump shot so then it works good sometimes, but not at other times. In the case of a racing carb the person might need to change bleeders in the metering blocks. Once you have the transfer tuned just right then you can adjust cam and nozzle size. What kind of cam profile do you need, then adjust nozzle once cam curve is right. You actually want to turn that nut you turned with the feeler gauge in place and engage the arm a little more. You want it to be that feeler gauge thickness before bottom out. Just before bottom. Just barely touching the arm is not enough. You're running a yellow cam, you're far from bottom out on that 50cc pump.
Very very nice. It's good to see what people on the other side of the pond use. A double pumper carb by Holley. We Europeans have to do with Webers which are not bad at all, but talk about S.U's and strombergs. Pretty useless. Thanx for the video.
You are right about the size of this pump, its a 50cc unit, there are upgade kits to convert the smaller 30cc to this one, I also just love the easy to use sight glass on these carbs
If you have a hesitation like as if the ignition cut out for a fraction of a second then its not enough fuel, if the engine is slow to respond when you hit the throttle but does rev up then its likely to much fuel
I used to have an old 780 holley on my 427, the acc. pump was much smaller than yours, back in the day they did have larger/higher volume pumps, i think they were called RIO acc. pumps-- I like the sight plugs on your carb, sure beats taking out the plugs and checking with the engine running
Not a bad video. You need to mention however that when you adjust your idle you need to recheck your pump adjustment. Due to how the cam on the throttle shaft works it will warrant the need to readjust.
It makes my day to hear a comment like yours, thank you very much, yep no air filter, keep in mind that the minutes a drag race engine runs in a year is very low
Well adjusted it this morning and took it to the next town. I think it pretty much took care of the issue, other than i had my choke off as well. fixed the choke once i got there and it runs great now. still has a little stumble. Not right when i hit the throttle, but slightly afterword. Thanks for the video though! alot nicer to drive when it runs good.
If it's slightly afterwards, it's probably the power valve. If you have a 6.5 installed, try going to a different number. The bigger the number on the valve, the sooner it will give you the gas.
Thanks for posting this I'm going to try this on my truck but I thing my problem is to much fuel I have a ford inline 6 300 bored 60 over with a older untouched Holley 600cfm carb.
This is why the Nissan Skyline is sooo effective, the analogue type bodges have been taken out by digital fixes. I'm not suggesting that digital is the panacea, but it gives you better averaging, when you set up these things, you will often set then cold or cool, 'cos the don't make fingers out of asbestos....and then when running, the tolerances will change, and good, well thought out digital can make a better fix. Look at OBD2 and think of the possibilities that that tech could make.
Awesome. My 72 Chevy k20 with a 396 is running a Holley street avenger 670. I have to feather the throttle every time I hit the gas. I bet this is the problem.
Watch for a video I have coming up shortly called Epanding foam pressure experiment. In the middle of that vid there is a one or two minute update on the suspension project
I thought power valve numbers do not affect idle at all. If your engine pulls 8", and you put a 10pv in it, it will not be dribbling fuel, because they work off of different /seperate circuits. Now, I think if you have fuel dribbling out of the boosters on idle, you should lower your float level.
I love your videos Groutaone! Im actually having a REALLY bad day today, but your vieos makes me think about something else, thank's alot for awesome videos! I have one question, what do you do for a living? You sounds like a guy who have "enough" money - Or you'r just good with money?
Some guys use fuel injection, the problem is they are very costly if you want to feed lots of power, engines with a few hundrd horsepower can be fed with wrecking yard injection setups, 1000 horsepower not so much
You may have a 50cc pump cam operating a stock 30cc pump, parts get swapped around over the years, never take for granted things are put together correctly when you get them, have you got another carb you can compare the cam and pump arm too?
What would you if after adjusting you found that the accelerator pump arm was bottoming out? Also have you ever delt with the carb being to far into the main circuit at idle? If so have you ever drilled your throttle blades to help get more rpm and close your idle screw.
Great tip and car sounds awesome! I noticed at the end of the vid that the front pumps seemed to be more sensitive / responsive compared to the rear, is that anything to worry to worry about or maybe it was just the rears weren't setup? Or i should just stop typing ;) Cheers!
I just realized that carb knowledge is becoming scarcer by the year with fuel injection so common now. Our younger folks don't really have any experience with these anymore. I like injection , but love carbs for their simplicity and reliability.
I know this is an ancient post now, but your car revs sooo quick. I don't see a MSD multispark 6AL box. Didn't use one? If not, I guess you didn't need one. Also, do you remember the weight of your flywheel? and is that a remote start on right behind the engine on the top of the firewall? Legit man!
I don't have the car anymore but I think I had a 7-AL3 mounted in the car, yes that is a remote start without ignition and the other one beside it if I remember right is for the fuel pump. Flywheel will have been a normal weight competition AT flywheel.
Have no fear its a winter project, if you notice all my videos lately are ones that I can only make outside in summer and now is the time to make those, there will be lots of time in winter for indoor projects
That's what I think it is... the orange pump cam operating the 30cc pump (smaller pump) so I reversed accelerate pumps to front and rear bowls and the 50cc pump was adjustable with the orange cam. I am confused though, does the 50cc pump go in the rear or front bowl? Also which color cam do you recommend for the 30cc pump? Thanks!
I feel bad bringing it up .. but I would love to know what happened to the sand rail .. did you finish it ? Sell it ? Hide it away ? .. it’s been almost over 6 years . And I think about it from time to time .. just wondering.. . I used some of your fabrication ideas and have since built a few fun vehicles for my kiddos .. . Thanks for your time
@@groutaone is their thought of workin on it in the future? Even if you don’t use it for videos.. Maby just give an overview of it finished. That would be awesome to see .. and it would give closure .. thanks for replying
That engine is the sound of heaven... love it!
Probably worth noting, adjusting the pump cam arm play is a good cure for the stumble issue, provided the carb has already been tuned to the engine, and has previously run well.
But if this is a different (new) carb, being used on an engine for the first time, it may not be the accelerator pump that is causing the bog. It could also be too big of a pump nozzle size for the engine.
I had a similar issue when I installed a 450 Holley on a stock 305 GM engine. After tuning the air screws to obtain good vacuum, and having set float height, curb idle, pump cam preload, ect, I still had a stumble.
The Holley pump nozzle was a size 31, and it would bog/hesitate right off idle. This was due to to much fuel being pumped in by the accelerator pump. Changing to a size 25 pump nozzle completely took care of the issue. Just thought this was worth mentioning.
Great videos!
Or too small jet size
How do you know what size nozzle you have ?
@@leeroybodell2403
There are numbers on the squirter nozzle that indicate the orifice size in thousands of an inch.
Been watching summit videos and all sorts of others couldn't get what they were talking about...+++ very informative you thoroughly explain and illustrate everything perfectly.keep making videos you are a good teacher!
Man this thing sounds killer!! Nothing sounds better than a built big block chevy
Great explanation. I especially like how you showed the using the feeler gauge to make sure you don’t bottom out the pump.
Excellent video! I went right out and checked mines and yes sir there's plenty of play so now I know where to start. Thanks
The back one comes on a bit later because of the linkage design, it perfoms the same, just a delay as the front opens sooner
Very helpful , Thanks , I'd like to spend a couple hours with you learning more about carb's . Some people are easy to understand and some are too technical . I can understand you . Once again ... Thank's .
Thank you! This was exactly the problem I had with my new Holly.
Thanks for your help. I changed my carb and got a back fire and stumble. Your video will help I'm sure. Cheers
One of the easiest ways to determine your accelerator pump setup is to just warm it up and push down on the pump adjustment nut and feed it a shot of fuel. If it bogs shorten the spring, if it likes it expand it
I think its more the shooter size that affects fuel delay, the bigger it is the faster the spring can recover, but the important thing is how well the engine responds. Shooter size is a good place to tune if engine still doesnt respond as it should
Thanks for your comments, my goal is to minimize crankcase pressure during high rpm racing conditions which makes more power that way and is safer for seals and gaskets, during wide open throttle the engine makes almost zero vacuum so a small diameter PVC hose will do very little in that regards so I don't bother with it, I use a large capacity breather instead
yeah the double pumpers are cool and the fact that it has an extra accelerator pump for the back is what make them cool. I'm at the point where im going to start messing with those fancy ones like you have though. at the moment I still run a normal holley 800 double pumper
i learn something in your videos every time i watch them ! great car great video :P
i swear every vid is always informative and informational..so glad i subbed your channel some time ago..too cool
Thanks for the response from what you said I'm having a rich issue which is what I was leaning towards because I have friends tell me all the time that they can smell the gas when I pass them. I guess the next thing on y list to buy is a jet kit and a accelerator pump cam kit along with the vacuum secondary spring kit because my secondaries aren't opening all the way either.
Cool vid my friend...very interesting.
OH if a Holley was only that easy.
Pump cam and nozzle size combo can be the biggest challenge you ever faced. Also, the transfer circuit comes in to play. If the butterfly are too far open, or not open enough. How rich or lean is the transfer. Maybe the bog is a lean transfer and your covering it up with accel. pump shot so then it works good sometimes, but not at other times. In the case of a racing carb the person might need to change bleeders in the metering blocks. Once you have the transfer tuned just right then you can adjust cam and nozzle size. What kind of cam profile do you need, then adjust nozzle once cam curve is right. You actually want to turn that nut you turned with the feeler gauge in place and engage the arm a little more. You want it to be that feeler gauge thickness before bottom out. Just before bottom. Just barely touching the arm is not enough. You're running a yellow cam, you're far from bottom out on that 50cc pump.
Very very nice. It's good to see what people on the other side of the pond use. A double pumper carb by Holley. We Europeans have to do with Webers which are not bad at all, but talk about S.U's and strombergs. Pretty useless.
Thanx for the video.
You are right about the size of this pump, its a 50cc unit, there are upgade kits to convert the smaller 30cc to this one, I also just love the easy to use sight glass on these carbs
If you have a hesitation like as if the ignition cut out for a fraction of a second then its not enough fuel, if the engine is slow to respond when you hit the throttle but does rev up then its likely to much fuel
No, it goes down all the way even with slop and play in the arm...
Appreciate your help.
I used to have an old 780 holley on my 427, the acc. pump was much smaller than yours, back in the day they did have larger/higher volume pumps, i think they were called RIO acc. pumps-- I like the sight plugs on your carb, sure beats taking out the plugs and checking with the engine running
The first two seconds made my day
Not a bad video. You need to mention however that when you adjust your idle you need to recheck your pump adjustment. Due to how the cam on the throttle shaft works it will warrant the need to readjust.
I think you nailed it when you said the vacuum secondarys dont open all the way, fix that and you should have it made
Slick trick, glad you solved it
Glad to help, the hose is to prevent fuel slosh out of the vents
Big thanks for being one of them
Great video
I like that we gave a demo on fixing carb hesitation and we didn't hesitate to give the throttle a manly stab not some sissy little rev.
Great video, thanks for the upload!
It makes my day to hear a comment like yours, thank you very much, yep no air filter, keep in mind that the minutes a drag race engine runs in a year is very low
If it bottoms out try a different pump cam position or different cam, the hole trick does work and its good to run the blades up on the slot for idle
Good stuff Buddy!! When that happens on the Bike we just call it a Harley Sneeze!!☺
Well adjusted it this morning and took it to the next town. I think it pretty much took care of the issue, other than i had my choke off as well. fixed the choke once i got there and it runs great now. still has a little stumble. Not right when i hit the throttle, but slightly afterword. Thanks for the video though! alot nicer to drive when it runs good.
If it's slightly afterwards, it's probably the power valve. If you have a 6.5 installed, try going to a different number. The bigger the number on the valve, the sooner it will give you the gas.
Really appreciate the tip, thanks
Had that problem a many of times!!
Those holley's are real "finnicky"(?) and sensitive if ya will and need the right adjustments fuel/air to get the best out of em. good upload/info.
Thanks for posting this I'm going to try this on my truck but I thing my problem is to much fuel I have a ford inline 6 300 bored 60 over with a older untouched Holley 600cfm carb.
Tremendous help. Thanks bro!
great video once again Groutaone
ever had problems with the spring on the arm delaying the proper amount of shot needed. yours appears more beefy than the standard holley.
Thanks for having a look
At wide open can you grab the pump arm and move it further down by hand, even just a little?
Interesting video never knew that about Holy dual pumper. :-)
Power valve then the squirters then the accelerator pump then then the jets pick up a holley book
Nice video.
Good video, thanks for making sense. Now can you do one that shows how to adjust for transfer slots when they’re over exposed in idle?
such an awesome souding engine my friend! but still anticipating a update on the buggy and busa engine! but keep it all coming!
dominating holley!!!
Yep, normally a Dominator is 1050, 1150 or 1250 but they can be made bigger with mods
Usually the arm is adjusted correctly, the problem is most likely too small of a squirter, buy a larger # pair of primary squirters.
They also look cool on the kitchen table, so long as the wifes not home
Love that car.
Yaaa. it was in that other vid.. this video explains it better though and shows more about the carb anyway.
This is why the Nissan Skyline is sooo effective, the analogue type bodges have been taken out by digital fixes. I'm not suggesting that digital is the panacea, but it gives you better averaging, when you set up these things, you will often set then cold or cool, 'cos the don't make fingers out of asbestos....and then when running, the tolerances will change, and good, well thought out digital can make a better fix. Look at OBD2 and think of the possibilities that that tech could make.
Awesome. My 72 Chevy k20 with a 396 is running a Holley street avenger 670. I have to feather the throttle every time I hit the gas. I bet this is the problem.
Watch for a video I have coming up shortly called Epanding foam pressure experiment. In the middle of that vid there is a one or two minute update on the suspension project
Great video thank you!
Great video. That thing sounds mean.
You can do in the middle of my town, like you said, if you're not making a ruckus. I take my quad on the smaller back-streets.
Check if the carb dribbles fuel out the booster at idle, if it does you need a power valve with a lighter spring
I thought power valve numbers do not affect idle at all.
If your engine pulls 8", and you put a 10pv in it, it will not be dribbling fuel, because they work off of different /seperate circuits.
Now, I think if you have fuel dribbling out of the boosters on idle, you should lower your float level.
even start! both paddle tires :P that would be soo awesome to watch :P
wow thanks bro man this work for me.
I love your videos Groutaone! Im actually having a REALLY bad day today, but your vieos makes me think about something else, thank's alot for awesome videos!
I have one question, what do you do for a living? You sounds like a guy who have "enough" money - Or you'r just good with money?
Its his winter project. Thats pretty normal he doesnt do much on it during summer.
Some guys use fuel injection, the problem is they are very costly if you want to feed lots of power, engines with a few hundrd horsepower can be fed with wrecking yard injection setups, 1000 horsepower not so much
Last few days its been warming up, was close to 80F yesterday, I dont mind though in winter sometimes we get -40
good sir, i love that fucking sound.
Say you may be right on that, I dont remember did I show this adjustment in that video?
(Also both pump cams are the orange ones set at #1 if that helps)
The problem I am having on my HP750, is that when I adjust the slack out of the pump, I don’t have any clearance between the pump arm and lever at WOT
Bet you cant wait to have a look, let us know what you find
pretty sweet vid, nice to see a raw fuel guzzling machine,,,, fuel goes in horse power come out :p
You may have a 50cc pump cam operating a stock 30cc pump, parts get swapped around over the years, never take for granted things are put together correctly when you get them, have you got another carb you can compare the cam and pump arm too?
You should make a video of all of your cars, bikes and toys
What would you if after adjusting you found that the accelerator pump arm was bottoming out? Also have you ever delt with the carb being to far into the main circuit at idle? If so have you ever drilled your throttle blades to help get more rpm and close your idle screw.
There's something satisfying about watching that engine eat up fuel.
Great tip and car sounds awesome! I noticed at the end of the vid that the front pumps seemed to be more sensitive / responsive compared to the rear, is that anything to worry to worry about or maybe it was just the rears weren't setup? Or i should just stop typing ;) Cheers!
haha... pretty sure the pontiac would definitely win a roost contest ;)
I just realized that carb knowledge is becoming scarcer by the year with fuel injection so common now. Our younger folks don't really have any experience with these anymore. I like injection , but love carbs for their simplicity and reliability.
Great vid :)
I know this is an ancient post now, but your car revs sooo quick. I don't see a MSD multispark 6AL box. Didn't use one? If not, I guess you didn't need one. Also, do you remember the weight of your flywheel? and is that a remote start on right behind the engine on the top of the firewall? Legit man!
I don't have the car anymore but I think I had a 7-AL3 mounted in the car, yes that is a remote start without ignition and the other one beside it if I remember right is for the fuel pump. Flywheel will have been a normal weight competition AT flywheel.
Does the accelerator pump have any effect on idle?
my Holley runs VERY rich at idle and the guy who installed and adjusted the pump wayy wrong.
The only thing that could damage the engine here would be too much rpm without a load, it has a rev limiter however
cool like i said youre awesome man when we going to see some more of the buggy project? would be nice to hear that thing fired up at somepoint
Who gets a head start ?(Firebird would have paddle tires)
I say this a lot to people but its true, I really appreciate you watching my vids, thank you
I thought the .015 gap is between the nut on the top side rather than between the bolt and lever. Have I been doing it wrong? Thanks for the vids!
Cool
Thank you
Well glad my video helps your day, unfortunately I dont have enough money nor am I real good with it
Have no fear its a winter project, if you notice all my videos lately are ones that I can only make outside in summer and now is the time to make those, there will be lots of time in winter for indoor projects
I thought I remember you doing this video before. Still love the videos though
What purpose does the fuel line on the fuel bowls serve? Is it to keep the fuel in the bowels at launch? Thanks
What’s the purpose of the hose going from vent to vent
That's what I think it is... the orange pump cam operating the 30cc pump (smaller pump) so I reversed accelerate pumps to front and rear bowls and the 50cc pump was adjustable with the orange cam. I am confused though, does the 50cc pump go in the rear or front bowl? Also which color cam do you recommend for the 30cc pump? Thanks!
I feel bad bringing it up .. but I would love to know what happened to the sand rail .. did you finish it ? Sell it ? Hide it away ? .. it’s been almost over 6 years . And I think about it from time to time .. just wondering.. . I used some of your fabrication ideas and have since built a few fun vehicles for my kiddos .. . Thanks for your time
Hello, I still have it and never finished it, it sits in my garage.
@@groutaone is their thought of workin on it in the future? Even if you don’t use it for videos.. Maby just give an overview of it finished. That would be awesome to see .. and it would give closure .. thanks for replying