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Old 10-15-2009, 01:17 PM
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Trouble shooting Holley carb

It's a Holley 4160, list 9834 w/ vac secondary. Pre '92, so i installed check ball kit after blowing out power valve. Floats and acc pump set per Holley specs.
Car pulls strong on hwy. Problems are: (1) too rich mixture fouls plugs, carbons exhaust and will not idle down below 1000 rpm. (2) primary float bowl leaks down o'night. On starting engine will pop through exhaust until primary bowl fills to preset float level. when i installed check ball kit also installed Holley Trick kit. I followed Holley's instructions to drill, drop ball, followed by tapered end of spring and cap. Saw other internet articles recommending tapered end of spring first, followed by ball and cap. Anyone recall how they did this? (3) bottoming out the idle adjustment screws has no affect on the idle!


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Old 10-15-2009, 05:49 PM
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from wat it sounds like, u might have a stuck float or bad needle & seat... thats why its running rich, just keeps dumping fuel in, and when you go below 1000 rpm its getting to much fuel and dies (flooding engine) or ur needle & seat is dirty or bad letting more fuel in even when the float has it closed... thats why the mixture screws wont do anything getting to much fuel. Do you have fuel coming out the breather tubes on top?? try while the engine is running take a bottom of a screw driver and tap on the fuel bowl some times that will get the float unstuck or gett the dirt out of the seat... other than that i dont really know... just trying to help. Mark.
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Old 10-15-2009, 06:03 PM
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Sounds like a bad power valve or a bad gasket on the power valve. make sure the float level is adjusted and the needle and seat is not sticking. Was this carb on this engine and running before it blew the power valve? is it a 6.5 valve?
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Old 10-15-2009, 06:05 PM
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Might want to pull the primary bowl and metering block and re-check the powervalve installation. Pay special attn. to the gasket on the power valve to metering block location as it is easy to get off center because the recess flange on the powervalve is so shallow. If it's a little crooked it won't seal the powervalve to the block correctly and leak fuel through to the vacuum chamber on the carb body and go straight down the vacuum port, through the carb base and into the intake. This might explain where the fuel is going overnight, and the fast idle speed. A stuck inlet valve or bad float doesn't explain why the bowl is empty in the morning or after sitting for several hours. Also, make sure you put the right gasket on the powervalve. Some have three holes in the valve and some have two holes. There is an illustration in the direction sheet about this and if you use the wrong one,
the valve won't work properly or leak fuel.

Last edited by sqzbox; 10-15-2009 at 06:14 PM.
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Old 10-15-2009, 07:38 PM
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carb

What is your initial and total timing???

Keith
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Old 10-15-2009, 07:59 PM
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Trouble shooting Holley carb

Mark: No fuel rising out the breather tubes. All new floats, Viton needles, but when I go back into the primary metering block to check the power valve as Solidaxel and Squezbox recommended, I'll check the needle and seat, etc. Yes, the valve is a 6.5, and before the valve blew the carb performed well, considering it had been on the car since I bought it in'87. The gasket not seating properly would allow fuel to find its way straight into the intake. Could it be possible that on starting the engine the hot exhaust gases find some of that fuel and causes a backfire through the exhaust? Would a leaking power valve contribute to the high idle (1000rpm)?

Thanks for the tips.

Joe
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Old 10-15-2009, 08:34 PM
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trouble shooting Holley carb

Keith: Initial timing is 8* bftdc. I'm not sure what total advance I'm running. Distributor is a Mallory Unilite.


Joe
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Old 10-15-2009, 08:35 PM
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Improper seating of the gasket, draining the bowl overnight will leave raw fuel on top of the closed valves and leak into the cylinders with the one's that the valves are open on. Think of it as dumping to much fuel down the carb when trying to prime an engine that has run out of gas. as far as the high idle, if the power valve is leaking while the engine is shut off, imagine what it's dumping while it's running under pressure. You can't see it leaking into the engine while it's running because it's leaking out of the bottom of the base plate through the vacuum channel connected to the primary's under the throttle blades.
As K-STAR asked, your timing may be a little too far advanced causing the back fire in the first place. I would try and correct the over rich problem first
before the timing as you don't want to be starting no fire's ! I learned my lesson the hard way! A good fire extinguisher is halon, co-2, or if you don't have either, a wet soaked bath towel to toss over the carb just in case as the wet towel won't catch on fire. ABC powder just makes a mess of everything.
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Old 10-15-2009, 08:38 PM
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Another idea, after you shut the engine off, open the throttle wide open and look down the primary;'s and see if there is any fuel leaking into the intake.
use a strong flashlight, it will be hard to see.
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Old 10-16-2009, 08:33 AM
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Trouble shooting Holley carb

Engine is 327 Chevy with mild performance cam with .440 lift and 260* duration.
Stock 300 h.p. 327 called for 4* adv, so I"ll retard it and see what effect it has.
Going to look down the primary and see if there's some fuel running. The Trick Kit came with the blue gaskets and a 6.5 valve. Got the extinguishers handy!


Joe
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Old 10-16-2009, 10:06 AM
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HOLD ON MAN, you said nothing about having a performance cam in there!
If you don't have it set at more than 4* at idle, you need some advance, at least 10* or better initial. That explains some of the backfiring esspecialy on cold start's where the engine need's more fuel. I had a crower with 280D/460lift and no choke and couldn't go anywhere before it sat and warmed up. It hated cold start's.
Everything else we talked about applies to your problem though.
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Old 10-16-2009, 09:01 PM
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trouble shooting carb

Squezbox I had to temporarily pull off carb and won't be able to get back to it til next week, so I have not changed the initial advance from the 8*. I've got another '57 Chevy with a comp 280H cam in a 350. It runs best with 14* advance. It too has no choke, so this time of the year I don't go anywhere in it til it warms up. It has the 4776S, 650.

Appreciate the help.

Joe
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Old 10-16-2009, 09:11 PM
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Quote:
Originally Posted by Joe DA
It has the 4776S, 650.
That would be the 600 DP. 4777 is the 650, not that it matters in this instance.

Good luck!
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Old 10-18-2009, 01:40 PM
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Trouble shooting Holley carb

Right on Cobalt327 . My 4777S runs so good in my 350 that I've been thinking about that series of Holley d.p. for my 327, (4776, 600cfm), if I can't get the 4160 straightened out.


Joe DA
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Old 04-09-2010, 08:00 AM
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Hey, I know this is an old post. Just wanted to let you guys know, sqzbox hit the nail on the head for my issue. There was soo much gas that when I pulled plugs fuel would pore out. Turned out a small rip in the gasket and a mis-placed power valve gasket caused it all. Thanks Much.
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