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New build, Holley problems

June 18 2017 at 12:52 PM
Jason  (Login 60sIron)
Members

This engine has been run on the dyno, but today was the first time in the car.

On the dyno, it ran with a borrowed distributor and carb. Now in the car, it is set up with a Holley 750 vacuum secondary and a stock distributor with Pertronix ignitor ignition module.

The engine is:
4.165 x 4.125
Comp hydraulic roller cam
BBM heads

It runs, but idles rough, and seems to want a lot of spark advance. The vac advance is disconnected.

I've stopped trying to work on it today because I think the carb is defective. I'm getting dripping gas from the rear fuel bowl area. I can't see exactly where it is coming from. This is the first Holley I've worked with, my other FEs ran either the 4100 or an Edelbrock. There were a few backfires through the carb as I was setting the initial timing, I've heard that Holleys don't react well do those, could I have blown something that is causing this fuel leak? Did I destroy this carb, or should I try to return it?

Clearly there is something wrong with this carb with the leak, but could it also be causing the idling problems?

 
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Anonymous
(Login coupe3w)
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Re: New build, Holley problems

June 18 2017, 1:03 PM 

Back fire will ruin the power valve. Did you adjust the floats or just through it on?

 
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Jason
(Login 60sIron)
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I didn't adjust the floats

June 18 2017, 1:49 PM 

I just bolted it on with the expectation I would adjust it after I saw how it ran. Will a float adjustment cause a fuel drip out the back? On a 4100 misadjusted floats causes gas to come out the vent holes on the top. Will a blown power valve cause gas to leak out the back?

Guidance is much appreciated, I'm new to Holleys


 
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Button
(Login cliffrod)
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Does "just bolted it on" mean...

June 18 2017, 2:08 PM 

Putting a old, used carb on and hoping for the best? If so, that's often good for an initial,leak until gaskets swell. This swelling may or may not stop leaking problems.. Other dried up parts may quickly fail, like a power valve in general use whether it suffers through backfires or not...

Rebuilding a Holley isn't hard. Float levels can be easily adjusted. Lean conditions , like too small a squirt from the accelerator pump (bad diaphragm, incorrect arm adjustment, cam on throttle main shaft, are not hard to fix. That leak on the back may only be a loose bowl screw. But you need to start with a carb in good condition, whether fresh off a running engine or properly rebuilt.

If you're comfortable with rebuilding a 4100, a Holley is more similar than something like a quadrajet.

1967 Galaxie 500 Red original Q code 428
1967 Galaxie 500 White with Black stripes 428PI clone- car is dead & long gone, sold near Oak Ridge TN 2000, would love to find it.....
Please visit http://carolinasculpturestudio.com/ for pictures, information and video links to my work.

 
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Jason
(Login 60sIron)
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It is a new carb

June 18 2017, 2:27 PM 

It is technically a reman, unit, but it was supposed to be ready to run.

 
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Button
(Login cliffrod)
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hopefully good news

June 18 2017, 3:03 PM 

For that leak, Check the bowl screws to see if they're tight. That's the easiest thing to check.

To adjust floats, remove the inspection screws on bowls (on sides of bowls) and adjust the float screw and locknut adjuster on top of the bowl until fuel level is even with bottom of inspection hole and fuel just barely leaks out. Then secure the locknut without changing adjustment and replace the inspection screws.

Backfires may have damaged the power valve. If so, the front bowl and metering plate needs to come off to check things. If valve is wet on both sides or will not hold pressure/vacuum it needs r&r. Plan on gaskets needing to be replaced then as well because they will tear if you haven't spent money buying spares. When you have spares, they usually come off just fine....

A lean condition may be due to the adjustment of the accelerator pump actuating arm (screw and spring) the plastic cam on the throttle main shaft (different profiles are available) and/or the position of this plastic cam on the throttle shaft (position can be changed by the attaching screw)

The air adjustment screws (on each side of metering plate) may need adjustment. I usually GENTLY bottom each, then back out one half to one full turn each and proceed to adjust each the same amount until the best idle is achieved- highest vacuum, most consistent rpm, whatever. If an automatic car, I was taught to do this adjustment with the car in gear and someone behind the wheel with their foot on the brakes. Shorty said "you need your car to idle right when it's in gear and being driven, not while it's just a' idling while in park..." and that made sense to me.

Things like jets, filing or milling the metering plate(s) and body flat and more also need address. Some remanufactured carbs are not cleaned adequately, so that defeats other properly operating/adjusted items.

This should get you started. There are a lot more educated Holley people here who have actually read the book. Maybe they'll post some opinions.
1967 Galaxie 500 Red original Q code 428
1967 Galaxie 500 White with Black stripes 428PI clone- car is dead & long gone, sold near Oak Ridge TN 2000, would love to find it.....
Please visit http://carolinasculpturestudio.com/ for pictures, information and video links to my work.

 
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Jason
(Login 60sIron)
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I checked to bowl screw plugs

June 18 2017, 2:50 PM 

They were both tight.

It is a slow leak which seems to be coming from the under side of the secondary fuel bowl. This particular carb doesn't have a metering block back there, so I'm thinking it is the bowl to throttle gasket that is leaking, let me know if there is something else it could be that is easier to fix.

 
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James H
(Login wookie1)
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What's your initial timing set at?

June 18 2017, 4:55 PM 

Are you sure there are no vacuum leaks?

Hold off on the power valve until you check other basic stuff. A blown power valve shouldn't leak at idle anyway. Make sure the floats are set right before doing anything else.

How many turns out are the idle mixture screws? What about the throttle stop screw?
James Hastings
http://www.fastlaneinnovations.com
'69 Cobra, 416FE, MS3-Pro EFI, TKO-600, RamDuct Ram Air System

 
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Bones
(Login boneyard51)
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Power valve

June 19 2017, 7:26 PM 

If you have a blown power valve it will leak into the intake all the time, idle, or wide open. You will only notice it at idle, as the engine can take the extra gas at higher speeds. Bones

 
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Falcon67
(Login Falcon67)
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Leak

June 19 2017, 6:23 AM 

Not sure what you tightened, but there a 4 bowl screws not two. A 750 VS has a metering block in the rear and there is a single gasket that seals the block and the bowl to the main body. You can tighten up the rear bowl screws - 4 and see if that stops it. If you have need to change the gasket, you'll need a clutch head screwdriver of the correct size to remove the metering block. I would also check the base plate screws.

After you get it to run dry, remove the float level site plugs on the side of the bowls, one end at a time - with the engine running - and adjust the flat level so fuel just touches the lower threads of the plug holes. You need a screwdriver and a 5/8" wrench. Turn the nut left to lower the fuel level, right to raise - little bit, like 1/16 turn - goes a long way so go slow and let the fuel level settle at the new setting before changing it again. Note that you have to loosen the lock screw just a bit, which will leak fuel from under the screw head.

Idle - start with the screws out about 1 1/2 turns unless its a 4 corner unit, then maybe 1 turn out on each. Turn in until the idle starts to drop, then back off about 1/8~1/4 turn. You'll go around a few times to get them all about the same, usually in the 3/4~1 out range.

Power Valve - If it's any kind of a newer model, there will be a check valve in the baseplate to protect against a backfire. I have been running Holleys for 45 years and I can say that I have changed power valves for age, rating, gasket replacement, etc but I have never actually seen or handles a "blown" valve. Typically they might have backed off or the gasket leaks. A lot of "blown power valve" issues - IMHO - are actually leaking main body gaskets, letting fuel into the wrong passages.

 
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Cammerfe
(Login ectarecordholder)
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My then-new....

June 19 2017, 9:49 AM 

'64 427 had to go back to the dealer for an idle problem. The tech showed me a power valve with the rubber loose (popped-out) along one side. Replacing it solved the problem.

KS

 
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