Fuel in intake
 

Has anyone seen this ? I have a 383 mopar stock engine and have been getting fuel fouled spark plugs and I see fuel on the plenum floor of the intake. It's dual plane intake, fuel is on both sides. I've been working on the carb (holley) thinking too much of the transfer slot is exposed. The heat passage is blocked, so I'm wondering is the fuel puddling up because I've blocked the heat passage which not letting the fuel atomize ? I thought I had fuel in the oil,but I had it analyzed and they didn't detect anything. I was thinking about putting hotter plugs in it and maybe that would burn the fuel off. any experience ??

Re: Fuel in intake
 

Overly rich or weak-marginal ignition system ---is it every plug or just one?

Re: Fuel in intake
 

Ignition should be good. Everything new, msd dist., daytona sensors box. I've checked wire resistance from inside of cap to plug, all good.


it's 6 out of 8 plugs, I'm thinking cyl. to cyl distribution of this intake is pretty bad. Once I get to fine tuning it, pretty sure it will have staggered jetting.


don't think its rich basically. fuel mixture screws are adjusted to rpm/manifold vacuum

Re: Fuel in intake
 

Pull carb off and keep the fuel line hooked up. Then hold it level and have someone turn on fuel pump and see where the fuel is leaking. It maybe a gasket that is allowing fuel to drain through a vacuum port into the intake.

Re: Fuel in intake
 

I've tried that Larry, not a drop. fuel pressure at 6#. When the engine is running, I can look down and nothing is coming out of the boosters. But when I take the carb off, the top of the base gasket is always wet. It's a 4 hole gasket to match intake. I'm missing something..

Re: Fuel in intake
 

What kind of accelerator pump do you have-did u check the vacuum plug too--try another carb see if it still persists

Re: Fuel in intake
 

What's your power valve situation?

Re: Fuel in intake
 

I meant power valve not vacuum plug

Re: Fuel in intake
 

I don't have another good carb to try. Accelerator pump is 30cc, PV is 2.5. This problem happens after just idling. I have a plug for the PV, yet to try it though. I guess I'll try to map out all the passages next. Also will post some pics.

Re: Fuel in intake
 

What is the list number of the holley carb.???

Re: Fuel in intake
 

List 4668

Re: Fuel in intake
 

is the base plate or carb body warped???

Re: Fuel in intake
 

might be on to something, base of carb body is warped .011", top of base plate is .002"


I think I'll find some socket head screws to replace the Phillips head ones.

Re: Fuel in intake
 

Well I made some progress. The screws are #12, so I didn't have any of those, so I tightened up the base plate best I could and ran it. The last few times I've run this engine,the vacuum floats from 8-12 in. with the rpm tracking the the vacuum, acted the same this time. Took off the carb and there was still fuel in the intake, maybe a little less. I took the carb base plate off and the base, body, and gasket were pretty much dry. Previously they were soaking wet. Far from a slam dunk, but it's worth pursuing. I think I will try to re-surface the body and get a new gasket.

Re: Fuel in intake
 

Ok, I have finally found the real issue here. I did end up re-surfacing the bottom of the body and that is sealed up well. My original thought was to take out the power valve, I never tried that. So after looking at the baseplate, a lightbulb flickered on. First picture shows how I originally had it put together, second one is the fix.

Re: Fuel in intake
 

So changing from a 4 hole to a open plenum manifold gasket solved your issue?

Re: Fuel in intake
 

It made a huge difference in the idle. from what I see, the first gasket blocked the source of manifold vacuum that feeds the PV. I think the PV was opening during idle. At least that is my new theory. Spark plugs are now dry as well.

Re: Fuel in intake
 

Make sure you have some sort of 4 hole gasket or something else, like a 4 hole thin spacer, to keep a base plate to bowl screw from getting loose and backing out and falling into the engine through the intake! Holleys do that.Could save you an engine.

Re: Fuel in intake
 

Thanks Greg. Good point. My theory #2 didn't pan out. Although I've seen fuel stains where there shouldn't be any, so trying a few things. Pretty annoyed with this carb as it's fresh from one of the name gurus, but I guess it's a good training experience for me.

Re: Fuel in intake
 

I think I've fixed this issue. I had thought the PV was opening because of the base gaskets. Well I found that fuel was collecting in the vacuum space in the body behind the PV, and was being pulled in thru the vacuum port thru the baseplate. Gaskets were leaking bad on both ends. I re-surfaced both ends of the body where the fuel bowls go. Amazing how bad a shape they were in once I started working on them. I will never build a carb without doing this. The vacuum space is dry on both ends now and spark plugs are also dry. Still a little fuel in the intake, not going to worry any more about that. I'll see how it runs. I won't mention who built this carb, but he was recommended in a thread I started here. Stevie Wonder could have diagnosed this problem. And thanks to all that helped. On to the next problem......

Re: Fuel in intake
 

Thought I should add this. I talked to the carb guy today, he apologized for how things went and offered to do another carb on his nickle. Can't ask for a better conclusion than that.

Re: Fuel in intake
 

Raw fuel through the vacuum port, I'm glad you found it.

Re: Fuel in intake
 

When i worked in the carb shop at AED in Richmond Va every carb we did we surfaced the ends of the body. Brand new castings from Holley are crap out of the box.

Re: Fuel in intake
 

If you remove the power valve and use the the Holley power valve plug some have excess casting flash on the head look at it some are worse than others. Bolt the carb together install both new gaskets and 4 bowl screw gaskets torque bowl screws to 35 in lbs. Then take it apart look for pv plug contact in the cavity the plug head goes in on the main body it can keep the metering block from totally sealing to the main body. I have seen that a lot.

Re: Fuel in intake
 

Thanks, I put the PV back in, but I'll keep that in mind