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holley carb tuning ?

Posted By: HotRodDave

holley carb tuning ? - 05/27/14 12:40 AM

We have a 650 holley double pumper 4777 on a 392 SB stroker ported magnum heads 10.2 compresison 222@.050 110 LSA 575 lift ported RPM airgap intake TTI headers, 2.5 dual exhaust 2.94 gears, mallolry ign. 32 degrees total in around 2000 RPM 18* idle around 850 idle, electric fuel pump 904 with low 1st and 2nd gears, stock high stall converter. It runs awesome, pulls like a monster at every RPM from idle to 6500 as long as you don't flat foot it. If you go from idle or even a little off idle to WOT it almost dies for a couple seconds then annihilates the tires almost instantly. It is in a 68 cuda. If you ease into it just a little there is no hesitation, only if you just flat stomp it.

Do I need 50CC acc pump? Mabey two 50cc pumps? Different pump cams? They are adjusted to start squirting instantly with any throttle movement. I have the float level set to just barely dribble out the level hole with the engine off and the pump on.
Posted By: MR_P_BODY

Re: holley carb tuning ? - 05/27/14 12:49 AM

I'd increase the squirters first
Posted By: ademon

Re: holley carb tuning ? - 05/27/14 12:55 AM

Even mild mopars I have had need big squirters, maybe try mid 30's. And a higher vacuum rated power valve.
Don't think the 50cc will help
Posted By: ajcasini

Re: holley carb tuning ? - 05/27/14 01:13 AM

Put a set of 032 squirters in it. Adjust the pump arms so you have around 040-050 play before the pumps squirt. This is about the size of 2 playing cards. This will help to keep fuel available to the pumps. If you are braking up to 12-1500 then flat foot it you have already pushed some fuel out of the pumps.
Posted By: HotRodDave

Re: holley carb tuning ? - 05/27/14 01:27 AM

It has 37 front and rear squirters in it.
Posted By: MR_P_BODY

Re: holley carb tuning ? - 05/27/14 01:37 AM

Quote:

It has 37 front and rear squirters in it.




You could be going dog rich with 37s... drop them to
about 32-34
Posted By: ademon

Re: holley carb tuning ? - 05/27/14 01:40 AM

Is the air horn milled?
Posted By: HotRodDave

Re: holley carb tuning ? - 05/27/14 01:45 AM

air horn still there, I will see if I have some smaller squirters
Posted By: HotRodDave

Re: holley carb tuning ? - 05/27/14 02:49 AM

I put a 31 in the front and that seems to help, the only other smaller one I have is a 28, should I throw that in the secondary?
Posted By: Locomotion

Re: holley carb tuning ? - 05/27/14 02:51 AM

What pump cams do you have in it and what # hole? You appear to not be getting enough initial squirt volume. 50cc pumps will simply prolong the length of the squirt with the same squirter size.

Try pink cam with the screw through the #2 hole in the arm and #3 hole in the nylon(?) cam I the primaries.

Secondaries the same, or green #2.

It takes some tinkering, but I try to get both squirt durations to finish squirting at the same time for drag racing only applications. You might need a slightly smaller cam. There are charts out there and pink & green are 2 of the biggest 30cc cams. #1 holes usually squirt less volume than #2/3.

Adjust for instant squirt with any throttle movement but keep about .015" additional compression at the pump housing lever when throttle is fully open.

I'll suggest going the other way on the squirters. If it still hesitates, consider .040"/.042"/.045".

I would suggest a power valve rated about 1.5 - 2 numbers above idle vacuum IN GEAR.

My theory is that your converter and gear isn't allowing the engine to rev up as fast as needed. The load requires more initial fuel until the rpm's and vacuum are high enough to get the main jets to take over.

(I normally use .037 - .040" squirters with pump cams as described with a low gear 904, 4.86 gears and a converter that flashes to 5100 - 5400 before starting to lock up.)

Can't guarantee it, but it's worth a try.

If, by chance, it goes when you flatfoot it, hesitates, then goes again, you may need bigger pump cams to extend the duration.
Posted By: HotRodDave

Re: holley carb tuning ? - 05/27/14 03:14 AM

Figured I could throw it in faster than I could get a guess. Now he is gonna have to get some tires that can hook, maybe some SS springs and spring clamps and slant 6 t bars cause it's blowing the tires away no matter how fast I stomp it
Posted By: MR_P_BODY

Re: holley carb tuning ? - 05/27/14 03:18 AM

Quote:

I put a 31 in the front and that seems to help, the only other smaller one I have is a 28, should I throw that in the secondary?




Try it for a test but it might be too small but you
should see a change
Posted By: DaveRS23

Re: holley carb tuning ? - 05/27/14 03:32 PM

Try a quicker opening power valve first, like a 9.5. Then start the accelerator pump tuning.
Posted By: Quicktree

Re: holley carb tuning ? - 05/27/14 04:04 PM

https://www.youtube.com/watch?v=gag-Bg-X8cM
Posted By: Thumperdart

Re: holley carb tuning ? - 05/27/14 04:47 PM

Quote:

What pump cams do you have in it and what # hole? You appear to not be getting enough initial squirt volume. 50cc pumps will simply prolong the length of the squirt with the same squirter size.

Try pink cam with the screw through the #2 hole in the arm and #3 hole in the nylon(?) cam I the primaries.

Secondaries the same, or green #2.

It takes some tinkering, but I try to get both squirt durations to finish squirting at the same time for drag racing only applications. You might need a slightly smaller cam. There are charts out there and pink & green are 2 of the biggest 30cc cams. #1 holes usually squirt less volume than #2/3.

Adjust for instant squirt with any throttle movement but keep about .015" additional compression at the pump housing lever when throttle is fully open.

I'll suggest going the other way on the squirters. If it still hesitates, consider .040"/.042"/.045".

I would suggest a power valve rated about 1.5 - 2 numbers above idle vacuum IN GEAR.

My theory is that your converter and gear isn't allowing the engine to rev up as fast as needed. The load requires more initial fuel until the rpm's and vacuum are high enough to get the main jets to take over.

(I normally use .037 - .040" squirters with pump cams as described with a low gear 904, 4.86 gears and a converter that flashes to 5100 - 5400 before starting to lock up.)

Can't guarantee it, but it's worth a try.

If, by chance, it goes when you flatfoot it, hesitates, then goes again, you may need bigger pump cams to extend the duration.




Some good ideas except for the p/v at idle deal. That`s old skool bs and even if it`s open at idle, it doesn`t come into play unless your way in the transfer slot on to the enrichment circuit. The proper way to tune p/v is to cruise the car and get a vacuum reading then go from there. Some guys go further for economy and hit a grade measure the reading and p/v it accordingly. I have bet. 9-10 "`s at a steady state cruise and put a 5.5 in and what a difference compared to the "old" idle theory. It get`s way deeper than this but that`s my position on this fwiw.........
Posted By: Quicktree

Re: holley carb tuning ? - 05/27/14 05:02 PM

Quote:

Quote:

What pump cams do you have in it and what # hole? You appear to not be getting enough initial squirt volume. 50cc pumps will simply prolong the length of the squirt with the same squirter size.

Try pink cam with the screw through the #2 hole in the arm and #3 hole in the nylon(?) cam I the primaries.

Secondaries the same, or green #2.

It takes some tinkering, but I try to get both squirt durations to finish squirting at the same time for drag racing only applications. You might need a slightly smaller cam. There are charts out there and pink & green are 2 of the biggest 30cc cams. #1 holes usually squirt less volume than #2/3.

Adjust for instant squirt with any throttle movement but keep about .015" additional compression at the pump housing lever when throttle is fully open.

I'll suggest going the other way on the squirters. If it still hesitates, consider .040"/.042"/.045".

I would suggest a power valve rated about 1.5 - 2 numbers above idle vacuum IN GEAR.

My theory is that your converter and gear isn't allowing the engine to rev up as fast as needed. The load requires more initial fuel until the rpm's and vacuum are high enough to get the main jets to take over.

(I normally use .037 - .040" squirters with pump cams as described with a low gear 904, 4.86 gears and a converter that flashes to 5100 - 5400 before starting to lock up.)

Can't guarantee it, but it's worth a try.

If, by chance, it goes when you flatfoot it, hesitates, then goes again, you may need bigger pump cams to extend the duration.




Some good ideas except for the p/v at idle deal. That`s old skool bs and even if it`s open at idle, it doesn`t come into play unless your way in the transfer slot on to the enrichment circuit. The proper way to tune p/v is to cruise the car and get a vacuum reading then go from there. Some guys go further for economy and hit a grade measure the reading and p/v it accordingly. I have bet. 9-10 "`s at a steady state cruise and put a 5.5 in and what a difference compared to the "old" idle theory. It get`s way deeper than this but that`s my position on this fwiw.........


thats the way you would do it for a street car but not drag only
Posted By: Thumperdart

Re: holley carb tuning ? - 05/27/14 05:18 PM

What? Not sure I understand your point Quick..........
Posted By: sixpackgut

Re: holley carb tuning ? - 05/27/14 05:41 PM

blue cams and 32 squirters. I also wont run a PV lower than a 6.5. I want it to open as soon as I mash the go pedal
Posted By: HotRodDave

Re: holley carb tuning ? - 05/27/14 06:26 PM

Thanks guys! It is already running 10 times better, I am gonna have to get it to hook up now before I can do any more tuning on pump shots

I also remember why I hate holleys, got to pull the fuel bowls and dump gas all over the engine to check PV and jet sizes
Posted By: FlyFish

Re: holley carb tuning ? - 05/27/14 07:29 PM

Quote:

.....

I also remember why I hate holleys, got to pull the fuel bowls and dump gas all over the engine to check PV and jet sizes




I use an empty play doh cup, pull one of the lower bowl screws...drains in seconds...no mess.
Posted By: Quicktree

Re: holley carb tuning ? - 05/27/14 07:59 PM

Quote:

What? Not sure I understand your point Quick..........


a race car never see's a cruise condition, and has nothing to do when the pv opens from an idle. like sixpackgut just said it need to open as soon as you mash the pedal on a drag car. my opinion is a race car doesn't even need a PV period.
Posted By: Thumperdart

Re: holley carb tuning ? - 05/27/14 08:03 PM

Lots of people think like this but I have other opinions but either way.
Posted By: Quicktree

Re: holley carb tuning ? - 05/27/14 10:20 PM

Quote:

Lots of people think like this but I have other opinions but either way.


thats fine, but remember a PV is nothing more than an on and off switch. if the size is correct it will come on as soon as the desired vac is reached. so actually on a race car that should be instantly. really no difference than a larger jet. and one less problem to have to worry about. my car see's WOT or on the idle circuit. not a lot more. now you being a street raced car is a different story.
Posted By: RobX4406

Re: holley carb tuning ? - 05/27/14 10:36 PM

Is the OP's car a race only piece?

Lots of people tune stuff different ways. Some still use total timing as the method on a car with an advance curve, even though cleaning up the idle characteristics can help the car leave on footbrake. Lots of ways to skin the cat.

My deal with a PV is to NOT have an extremely low numbered PV, 2.5, just in case the engine starts pulling a vacuum at high rpm/WOT conditions. That's where the select at idle using 1/2 vacuum guys can get killed. The time difference between a 5.5 and an 8.5 opening when you drop the hammer is so small it's not anything to worry about, manifold vacuum drops to nothing. Watch a gauge how fast it passes through the range when it's matted.

I've got some holleys that the arm on the throttle shaft has become loose. That actuates the pump cam slightly before the plates actually open. Make sure the gold arm isn't loose on the shaft.

Try disconnecting the secondaries and dial in the primary pump shot. Hook secondary up and see how it goes and tune that side. Trying to do both at the same time can be frustrating.

As far as the OP goes. Put an AF gauge in it to see what's occurring. Great tool to diagnose issues.
Posted By: Thumperdart

Re: holley carb tuning ? - 05/27/14 10:37 PM

Ya, I need a clean cruise AND plugs and now mine look like new after street driving and street racing...........
Posted By: DaveRS23

Re: holley carb tuning ? - 05/28/14 01:06 AM

Here is my experience with the power valve opening point for a street car;

When cruising in the 14.+ range, a late opening power valve (6.5 and lower numbers) can often result in a stumble with light additional throttle. 14+ A/F ratio quickly becomes 15 or 16:1 under even light additional load without additional fuel.

With an earlier opening point (8.5-10.5), the additional fuel comes in at a more appropriate time and prevents the stumble.

I do agree that when you stomp it (whether at the track or on the street) you blow past the opening point fast enough that it is far less relevant. But can still help or hurt in some situations, so it should receive some attention.

Most of the Double Pumpers I have dealt with have been plenty rich about everywhere, so I would be a little surprised if the OP's DP needed anything more than a bit of tweeking, if in fact his stumble is due to a lean condition.

Just my .
Posted By: AndyF

Re: holley carb tuning ? - 05/28/14 04:19 AM

Quote:

Thanks guys! It is already running 10 times better, I am gonna have to get it to hook up now before I can do any more tuning on pump shots

I also remember why I hate holleys, got to pull the fuel bowls and dump gas all over the engine to check PV and jet sizes




Buy the new bowls that have a drain plug. The new bowls are aluminum so they are lighter, use a AN o-ring fitting which works better and they have clear sight glass so you can easily set the fuel level. Ditch the old stuff and move up to the new stuff.

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