What causes a Holley to drain down overnight? - Team Camaro Tech
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post #1 of 11 (permalink) Old Jan 8th, 06, 05:41 PM Thread Starter
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What causes a Holley to drain down overnight?

There are no visible leaks. The front bowl goes way down overnight and dried up in 2 weeks time. Where can it leak internally into the intake?

When I shut the engine off and take the air cleaner off there is steam like vapor (gas vapor?) coming out of the carb.

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post #2 of 11 (permalink) Old Jan 8th, 06, 05:58 PM
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Re: What causes a Holley to drain down overnight?

powervalve leaking if you see no visible external leaks.

Don
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post #3 of 11 (permalink) Old Jan 8th, 06, 06:45 PM Thread Starter
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Re: What causes a Holley to drain down overnight?

Thanks. It started running very rich. Fowled the plugs today. Back to won't idle now.

Does backfiring thru the carb always mean overly advanced timing or could it be retarded timing also? If the idle drops to below say 800 rpm and it starts to die then stab it, it will sometimes backfire. The accel pump works with the least throttle movement and seems to be adjusted correctly.

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post #4 of 11 (permalink) Old Jan 8th, 06, 06:49 PM
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Re: What causes a Holley to drain down overnight?

If its backfiring then the power valve is gone but what is causing the back fire? Did you mess with something first?
Might want to dry out those plugs, replace power valve and while you're at it,, do a power valve blow out preventer kit to keep it from happening again.

Sounds like you got an older Holley. Most all the new stuff comes with the preventer.

Dont get too much fuel into crankcase past the rings,, will dilute oil.

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post #5 of 11 (permalink) Old Jan 8th, 06, 07:03 PM
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Re: What causes a Holley to drain down overnight?

a backfire is usually caused by retarded timing, but could be caused by crossfiring/burned plug wires





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post #6 of 11 (permalink) Old Jan 8th, 06, 07:23 PM Thread Starter
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Re: What causes a Holley to drain down overnight?

Got it to idle and run fine a few weeks ago. I set the timing back because it was idling with 35* including vacuum. It seemed like that was too much. That would trranslate to 20* initial and 28* centrifugal. Reading other posts I was trying to get it to run on 10*+15* at idle, but it would not. I think that is when I blew the power valve. I will not start it again until the PV is replaced

Another question on timing. I have an original timing cover and balancer. The balancer was rebuilt. The timing mark is about 10* advanced from the keyway. That puts it on the left edge of the large spoke on the DZ balancer (just like the pictures show it to be). Is there any way that TDC could be anywhere else? I know, I need to find TDC for myself. It just seems that the timing mark is not correct somehow if 35* is needed to idle. Isn't TDC built into the crank in relation to the keyway??

Plug wires arte new.

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post #7 of 11 (permalink) Old Jan 9th, 06, 06:12 AM
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Re: What causes a Holley to drain down overnight?

You are correct about needing to check for yourself TDC. You can use the spark plug hole method on #1 for checking. Sounds like you could have a slipped ring on the balancer also. You may not have to replace it just to read your numbers. If you can get them correct and get motor timed and find your problem,, BUT a balancer with a slipped ring is dangerous.

If you have access to a dial back timing light.. This may assist you in setting in total advance without having dist on a curve machine. You said 20 initial and total 28, thats 48* ? Did I read you correctly? Again, there are other issues that cause backfires. Its actually combustion at the wrong time. Ie. intake valve open during ignition so need to check that stuff first.

Drop a pv blow out kit into the carb cause looks like you will be needing it over time.

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post #8 of 11 (permalink) Old Jan 9th, 06, 09:20 AM
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Re: What causes a Holley to drain down overnight?

Blown power valve is my guess. Be sure to replace it before you start trying to sort other stuff out. Even if that is not the problem it will rule a major suspect out and cost less than $10 I believe.

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post #9 of 11 (permalink) Old Jan 9th, 06, 08:30 PM Thread Starter
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Re: What causes a Holley to drain down overnight?

Blow-out prevention kit was on the schedule for the next time the carb was off. I don't think the ring has slipped. It was rebuilt and revulcanized. The mark appears to be visually in the correct position according to pictures. I think the power valve has been blown since before I sent it off to JM. Both power valves and the blow-out kit this weekend should fix me. I will change the oil as a precaution also. I do have a dial-back light.

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post #10 of 11 (permalink) Old Jan 9th, 06, 10:31 PM
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Re: What causes a Holley to drain down overnight?

"What causes a Holley to drain down overnight? "

Any teen-agers in the house?

Definitely sounds like a power valve sucking/leaking fuel directly into the manifold.

I've had 3 factory dampners slip on me. All of them looked to be in excellent condition.
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post #11 of 11 (permalink) Old Jan 15th, 06, 11:28 AM Thread Starter
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Question Re: What causes a Holley to drain down overnight?

Well, it's not the power valves. I installed 2 new ones and backfire protection kit. I decided to bech test it with full bowls. Just the front bowl leaks down and it appears it is comming from the passenger side front bore only.

"Government is not reason; it is not eloquent; it is force. Like fire, it is a dangerous servant and a fearful master." ..... George Washington

Gary,TC Member with a Lemans Blue/Ivory 02D X33, DZ, M20, MS, flat hood. Only the BU code rear end is original.
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