carb hesitaition - squirter or?? UPDATE 9/2

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Thanks for all the input, it really helps to have all these experienced racers around here! Turns out I do have the pink cam, so that is one area I can likely impove upon.

Just to be clear on my bog/hesitation...I stomp the gas and the car leaves ok, then it starts to stumble/go in and out of power, then clears up around the 1st to 2nd shift and stays clear the rest of the run.

I'm going to try a 28 with the pink cam and if that doesn't help I will try a 42 (biggest and smallest I have). There is a vacant factory lot near my house with a ton of room to do some hard 1st gear launches. If neither of the squirters help any, I'll get on the horn with Jegs and order me up an accelerator pump tuning kit on Monday. trying to make the slicks night test n tune at DaGrove before my kids start school next week.

Sounds like your dumping too much fuel after the hit...
I'm a firm believer in the 50cc pumps.... its only
fuel in reserve if its not needed... the squirters
sound like they are too much .... JMO

after reading that.

Posted By: willp

Re: carb hesitaition - squirter or?? - 08/28/10 11:57 PM

Just to be clear on my bog/hesitation...I stomp the gas and the then it starts to stumble/go in and out of power, then clears up around the 1st to 2nd shift and stays clear the rest of the run.

This sounds like a problem with transitioning off the idle circuit to main feed from the boosters to me. If all the changes with cams and squirters doesnt help then you might want to have someone look into the carb calibration for your engine setup. Too low a front fuel level will also hinder the transition time also. Good luck with this I know how frustrating it can be.

Posted By: Dartman928

Re: carb hesitaition - squirter or?? - 08/29/10 02:37 AM

Tony

My suggestion would be vent tubes putting out

Posted By: 540DUSTER

Re: carb hesitaition - squirter or?? - 08/29/10 05:21 AM

What kind of fuel pump you running? To me it sounds like it runs good when you first nail it;then craps out until the first shaft.Could it be a pressure problem under high g forces?Just something to think about.

Posted By: TonyS451

Re: carb hesitaition - squirter or?? - 08/29/10 11:09 PM

well i tried putting the pump cam in 2nd hole and seemed to help a bit but still a slight hesitation. Tried 28, 33 and 37 squirters and they all seemed similar. I'm going to pick up a 50cc pump kit and hopefully that will solve the problem once and for all. BTW, why is it important to put the pump cam back to hole one on the street??

FWIW, I also swapped out my 4.5pv for a 3.5 - the 3.5 is better suited to my in gear vacuum reading as per Holleys recommendations. Anyhow, not expecting anything major, but could not notice anything different whatsoever.

Sooo, my neigborhood 1st and 2nd gear blasts were fun and all, but still working out the bugs... I'll keep you posted on the 50cc conversion.

Posted By: Quicktree

Re: carb hesitaition - squirter or?? - 08/29/10 11:58 PM

why don't you try a blue or brown cam before you buy the kit?

Posted By: TonyS451

Re: carb hesitaition - squirter or?? - 08/30/10 01:52 AM

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why don't you try a blue or brown cam before you buy the kit?

I would if I had them. My carb tuning parts are limited, so I figure I'll just buy the whole accelerator pump tuning kit that holley sells. I'm trying to get ready for this thursday and don't want to be missing anything I might need. I don't race very often, but I do enjoy testing and tuning...and I know i'll use this stuff again at some point.

Posted By: fishy340

Re: Carb - 08/30/10 02:04 PM

i agree pink pump cam,my tires came up after switching..it took that dead spot out completly

Posted By: Quicktree

Re: Carb - 08/30/10 02:47 PM

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i agree pink pump cam,my tires came up after switching..it took that dead spot out completly

after talking to him in pm's I don't think it's a pump shot issue at all. sounds more like he's running out of fuel right before the second gear shift. not off idle. the pink has the least aggressive profile but more fuel.

Posted By: Quicktree

Re: Carb - 08/30/10 03:06 PM

heres the chart
https://board.moparts.org/ubbthreads/upload2/5136759-HolleyPumpCams.pdf

Posted By: TonyS451

Re: Carb - 09/03/10 04:48 AM

Ok, so I get the 50cc pump kit and install it with the yellow cam it came with. It actually came with a brown one too, but it is thinner and for some reason the pump lever was only riding along the edge. It looked like eventually it could slip off. Either way, I figure the yellow cam is still a good option since it was only one of two included in the kit.

So I take it out for a spin and still the same sputtering crap. Turns out my linkage was binding due this goofy thick gasket I got from FBO. Thats a story for another post. I pull the carb off to replace the gasket and also try bumping up the fuel pressure to 8.5 lbs to see if that helps. I take it out for another spin and this time the car pulls hard like it has never pulled before! But heres the thing. When I pulled the carb off and on, I forgot to reconnect the hose from the back of the carb to the pcv. This hardest/cleanest pull ever was done with a hose hanging off the back of the carb vacumm port.

After scratching my head for a minute, I realized that the pcv was butted right up against the valve cover baffle and not allowing any room to breathe. We had to do a little "massaging" to the baffles to clear the rockers and never caught that.

So I connected a hose from the back of the carb to another vacuum port on the intake and for now the pvc is going to a seperate intake vacuum port.

After all this, could this have been a vacuum issue all along? I wasnt even sure the carb needed that port to function, I thought it was more for other accessories that require vacuum and otherwise capped. And how about the pcv, can I run without it? I do have a breather in the other valve cover. Now Im cornfused.

BTW, Is there any downside to running the 50cc pump?

Anyone ever heard of such goofiness before?

Posted By: joedust451

Re: Carb - 09/03/10 05:31 AM

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Ok, so I get the 50cc pump kit and install it with the yellow cam it came with. It actually came with a brown one too, but it is thinner and for some reason the pump lever was only riding along the edge. It looked like eventually it could slip off. Either way, I figure the yellow cam is still a good option since it was only one of two included in the kit.

So I take it out for a spin and still the same sputtering crap. Turns out my linkage was binding due this goofy thick gasket I got from FBO. Thats a story for another post. I pull the carb off to replace the gasket and also try bumping up the fuel pressure to 8.5 lbs to see if that helps. I take it out for another spin and this time the car pulls hard like it has never pulled before! But heres the thing. When I pulled the carb off and on, I forgot to reconnect the hose from the back of the carb to the pcv. This hardest/cleanest pull ever was done with a hose hanging off the back of the carb vacumm port.

After scratching my head for a minute, I realized that the pcv was butted right up against the valve cover baffle and not allowing any room to breathe. We had to do a little "massaging" to the baffles to clear the rockers and never caught that.

So I connected a hose from the back of the carb to another vacuum port on the intake and for now the pvc is going to a seperate intake vacuum port.

After all this, could this have been a vacuum issue all along? I wasnt even sure the carb needed that port to function, I thought it was more for other accessories that require vacuum. Now Im cornfused.

BTW, Is there any downside to running the 50cc pump?

Anyone ever heard of such goofiness before?

I said this before, & i'll still say it, if for any reason you need to jack around with pumps/cams to try & cure a stumble or bad bogg is not the cure, its just a bandaid for another problem that needs fixed, whether its in the carbs metering or ign. issues, This is not the cure, most cars (mopars) will run just fine with pink cams & 30cc pumps, look at alot of your Biggs carbs, Quik fuel & so on, they have in most all cases a 31-33 squirter F&R, 30cc pump F&R & pink cams, the only exception being the Dom., if your ign./timing/curve (no vacuum leaks) & metering is set properly for a given combo, all thats needed is fine tuning on the squirters/cams for best excelleration & 60ft., normally there relatively close OOTB.

Now that you "found" a potential problem, get that fixed, then i'd drop the 30cc pump back on with the pink cam & 31 squirter & try it again, you might be very surprized how it runs.

The PCV valve is to release gases from the crankcase, if it was clogged in any way, it will cause issues, most likely relative to what you were having, you can get away with blocking it off & running breathers on both VCs, either way the gases need to get out, emission laws wouldn't allow the gases to escape into the atmosphere, so they got re-burned through the intake, whether the port is on the carbs base or the intake, it gets pulled back in. The 1 way valve on the PCV is there incase theres an ign. backfire, you don't want the flame going back in the engine.

Posted By: Quicktree

Re: Carb - 09/03/10 08:30 AM

you mess with pumps,cams etc for the best 60'. after that it's a different issue. I bet it was fuel pressure causing it run out of fuel. a lot of race carbs come with 50cc pumps. if tuned right they are not a problem. you can run smaller squirters which I like.

Posted By: moper

Re: Carb - 09/03/10 12:22 PM

I'm not a big time racer but I've never had to use more than a 37 squirtor, and most are fine with 30ccs and 31. It's only supposed to pump during trasition in throttle opening. Not after... After is where the PV and booster come in. If I had to guess, your PCV is fine the way it was. The difference was the lean you had from basically a big vacuum leak. You have an annular booster carb. It's very sensitive to pressure cahnges. I'd go leaner on the shot (like a 28 with the 30cc) and see if that helps. Remember the amount of fuel will never change. It's always going to be 30 or 50ccs. But the time it takes to discharge will. Big squirtors mean a lot of fuel for a shorter time. Smaller shooters mean more time spent enriching the mixture. I think you're way over-rich when the rpms clear 2500 due to the annular boosters and larger pump cam with the larger shooter. It cleans out when the rpms drop with the shift and the acc pump is out of volume.

Posted By: TonyS451

Re: Carb - 09/03/10 01:50 PM

thanks for the replys guys. This has been a frustrating situation for sure. Moper - I did try the 30cc, pink cam and 28 squirter and had the same problem. I tried 28 to 47 squirters with the 30cc, and only tried 33's with the 50cc. Whats also very frustrating is that the problem never duplicates itself identically. Some pulls are cleaner than others, with the same hardware.

If the annular carb is more sensitive to pressure, would it help any to route the pcv to a port lower on the intake manifold vs directly to the carb?

Posted By: Quicktree

Re: Carb - 09/03/10 02:12 PM

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thanks for the replys guys. This has been a frustrating situation for sure. Moper - I did try the 30cc, pink cam and 28 squirter and had the same problem. I tried 28 to 47 squirters with the 30cc, and only tried 33's with the 50cc. Whats also very frustrating is that the problem never duplicates itself identically. Some pulls are cleaner than others, with the same hardware.

If the annular carb is more sensitive to pressure, would it help any to route the pcv to a port lower on the intake manifold vs directly to the carb?

why don't you just remove the pcv and add a vented cap? you really don't want to suck that into the mixture

Posted By: BradH

Re: Carb - 09/03/10 04:33 PM

What is the venturi dimension for a QFT "950" annular? Even running my Claw w/ 1.56" venturi and annular boosters, it seemed like that style of booster simply pulls too much fuel too early in the RPM range to run cleanly on the street.

If I ever try it w/ annular boosters again, I'm going to stick in the 1.59" venturi sleeves and see if that helps. Otherwise, I'm going to stay w/ "tried and true" downleg booster combinations.

Posted By: TonyS451

Re: Carb - 09/04/10 12:51 AM

not sure about the venturi size. I'll check into it though.

Posted By: willp

Re: Carb - 09/04/10 11:08 PM

If your 50cc stuff does not correct the problem I still recommend having the calibration of the meter circuit checked. You may have an air velocity problem with the heads that the annular booster cannot over come until the rpm picks up significantly increasing the port velocity. I would be more inclined to be using a down leg booster style carb anyway with more standard size pumps and squirters.

Posted By: TonyS451

Re: Carb - 09/05/10 12:17 AM

My engine guy thinks I should try jetting down a few sizes. His theory is that if the engine ran its best with a big vacuum leak, it must have been extremely rich (since normally a big vacuum leak would create a lean condition, especially on hard acceleration). He also thinks my problem is occuring past the point of the pump/squirter consideration. And, he also thinks the pcv is not part of the problem.

Soo, with that I'm going to pull the carb, put the 30cc and pink cam back on, 33 squirters (stock settings), and pull out 3 jet sizes. If that doesnt help any, I'm going to give another carb a try.

Can I route the pcv to a vacuum port on the manifold or is it best to go right to the back of the carb? Or does it not matter either way?

Posted By: willp

Re: Carb - 09/05/10 06:16 AM

Sometimes a big vacuum leak will cause the power valve to stand open all the time. And this would make it very rich. I think a power valve leak rich condition can be the same as 10 jet sizes big. But it also depends on how much of a vacuum leak there is. I would stick a gauge on it and see what it is doing at idle. I don't think it will matter one way or the other on where you attach the pcv hose. The orifice is usually with the pcv valve. I still believe the metering calibration is off on that carb. If you try another carb try one with down leg boosters. Good luck with this, I know how frustrating it can be.

Posted By: joedust451

Re: Carb - 09/05/10 06:59 AM

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I still believe the metering calibration is off on that carb.

I agree.

Posted By: Quicktree

Re: Carb - 09/05/10 02:07 PM

he added fuel pressure and it picked up. im still leaning towards it running out of fuel right before the shift point.

Posted By: 540DUSTER

Re: Carb - 09/05/10 04:44 PM

Did he add the fuel pressure before or after the regulator?

Posted By: Quicktree

Re: Carb - 09/05/10 05:33 PM

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Did he add the fuel pressure before or after the regulator?

have to guess it was after

Posted By: 540DUSTER

Re: Carb - 09/05/10 10:18 PM

if he increased regulator pressure,it reduces flow.Why does Barry Grant say that you need a pump that can pump,lets say one gallon in 20 seconds,its not because the engine is going to use that much fuel.Its because a pump that can flow fuel at that rate has a higher output pressure before bypass.I'am guessing that Tony's pump is going away.

Posted By: TonyS451

Re: Carb - 09/05/10 11:48 PM

I am running a clay smith mechanical pump and I really doubt the pump is going away. Cant say with 100% certainty especially since I still havn't figured this out yet, but the pressure is always rock steady wherever I lock it in at. I'm going to try jetting down first and see if there is any change. I will try different pressure settings too if need be. I will say this though, at my last test session when it ran its hardest with the pcv detached, I had the pressure up at 8.5. I kept the same pressure with the follow up pass (with the pcv attached) and it returned to the same breaking up symptoms.

Thats why I dont think its the pump or regulator...but im definitely not ruling it out entirely.

So tonight my test run will keep the 50cc pump, 33 squirter, jetting 3-4sizes down (forget what jets are in there now..I think 79 and 87). Going to keep the pressure at 8.5, and run the pcv hose to a port behind the intake.

If it shows signs of improvement or cleans it up all together, I may try going back to the 30cc and pink cam and also try dropping the fuel pressure to a more street friendly rate - 7-7.5.

Thanks everyone for your input. Its been very helpful.

Posted By: 540DUSTER

Re: Carb - 09/06/10 12:26 AM

Tony,can you monitor fuel pressure on a run? Is your fuel pick-up at the rear of the tank?

Posted By: TonyS451

Re: Carb - 09/06/10 01:17 AM

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Tony,can you monitor fuel pressure on a run? Is your fuel pick-up at the rear of the tank?

No, I dont have a a visible pressure gauge, only under the hood. The fuel pick up is a factory style 1/2" in a factory tank. And the fuel line from the tank to the pump is factory bent 1/2" steel. From the pump is -8 hose to regulator, and -6 hose from regulator to the carb.

Posted By: B1Fish540

Re: Carb - 09/06/10 04:26 AM

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I will say this though, at my last test session when it ran its hardest with the pcv detached, I had the pressure up at 8.5. I kept the same pressure with the follow up pass (with the pcv attached) and it returned to the same breaking up symptoms.

This is the part i dont get, Tony. If i understand it, it runs perfectly w/out the PCV hooked up? Plug that port and see how it runs, that will eliminate a bad PCV valve as the culprit. right? Or confirm it.

Posted By: TonyS451

Re: Carb - 09/06/10 04:38 AM

I made a few "runs" around the 'hood tonight. First I tried jetting down 4 sizes front and back with fuel pressure at 8.5, and sputtered like heck. Came back jetted back to 79 and 87 bumped the pressure up to 9 and ran much better, but still with some sputtering. When I set the pressure above 8.5 it appears to be too much for the regulator cause the needle starts bouncing. As soon as I back it off to 8.5 or below it stays steady.

I even popped the pcv hose off just to see if I could duplicate my awesome pull from the other night, but no such luck this time. I must have just been lucky last time.

I'm going to pick up a fuel pressure gauge that I can see from inside the car and really see whats happening. At this point, I think thats the only way to really narrow down the problem.

BTW, The car still idles like a champ and street cruising is nice and crisp, so for now I see no reason to put the 30cc pump and pink cam back in. I'll let you know what happens after I verify the fuel pressure on a "pull".

Posted By: willp

Re: Carb - 09/10/10 09:58 PM

You ever get this fiquired out?

Posted By: TonyS451

Re: Carb - 09/10/10 10:11 PM

I just plumbed a fuel pressure gauge in the other night (one that I can see while Im driving). Got too late to take it out for a "run" and havnt had a chance since. Gonna take it for a spin tomorrow...will let you know what i find. Thanks!

Posted By: Chris'sBarracuda

Re: Carb - 09/10/10 10:15 PM

What type of advance do you have on your Distributor?

Chris..

Posted By: TonyS451

Re: Carb - 09/10/10 10:36 PM

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What type of advance do you have on your Distributor?

Chris..

Got it set at 16 degrees mech advance - 20 initial and 36 total. No vacuum advance

carb hesitaition - squirter or?? UPDATE 9/2