Holley Avenger Carb

[Strawdawg]

If the float was sticking shut wouldn't the carb run dry? One fact of note, when I spent some time in Phoenix(almost a year), It never burped any fuel at all. Not even once. Moving to Phoenix from Denver created big time detonation problems which were eventually resolved by reducing the lead-in timing by 12 degrees. Now moved back to Denver, the problem has returned and of course the engine will not run with the reduced initial timing. Still "brainstorming" the situation...

yes, I should have said open...might want to check that it is set properly and cannot drop down too far

[bennydodge]

No problem man, I see your point, a float hanging up either way would certainly cause a problem. Floats and their movement are all checking out fine. 

[Strawdawg]

Then, it would seem to be one of a couple of potential problems.

Some is wrong with the needle or seat allowing fuel to keep coming in when it should be sealed off.

Or, you have too much fuel pressure. Holley says 5-7 psi.  I have gotten away with 8 in the past but somewhere in that range or higher, it may push the needle down and let the bowls overflow.

If both bowls are over-filled, I would suspect fuel pressure.  If only one is doing it, I would suspect the needle/seat.

I believe you have already checked the floats to make sure one is not heavier than the other...

[bennydodge]

Floats bowls have glass sights and the fuel level is set exactly in the middle per Holley's instructions. With the 870 on there, the engine throws off considerably more heat than any other carb I've used. The problem never happens with a cold or lukewarm engine. The plugs do read a little lean as well. I put the 870 back on a couple of days ago with a little richer idle mix and slightly colder plugs. After 40 miles (some of those miles spirited) the problem hasn't happened, but I've gone long stretches without the issue before so only time will tell..

[bennydodge]

Sorry to the OP! This was supposed to be about your setup and it regressed into a problem I've had. My opinion is to use that 770 first. If you run Edelbrock, I would use the 800 AVS.

[Chryco Psycho]

sounds like you should up jet 2 sizes on the front this should improve color & mileage as well as dropping the heat

[bennydodge]

My thought as well. When I got it I ran it box-stock. After a few hours of drive time I went down 2 sizes on all 4 corners-the engine was much snappier and crisp. It was many years ago so I don't recall every detail. The fuel burping problem happened that day as well. This prompted me take it apart at which time I found aluminum shavings in both bowls. I assumed this affecting the needle and seat operation. I live in Denver so jetting down seemed right-although the engine is NOWHERE near stock. The richer idle mix has darkened the plugs to an almost chocolate color with would seem to rich. I'll monitor the oil for any gas fouling.

[Chryco Psycho]

does it idle worse with the richer idle setting ? , generally you want the minimum fuel through the idle circuit before it drops idle speed Jeting affects it differently , altitude will affect jet sizing but also modified engines require different jetting , I would lean the idle mix out correctly & & let the engine tell you what jets it wants

[bennydodge]

The difference is slight at idle with it richer(smoother)-the throttle tip seems smoother as well. But, like I said, dirtier plugs. I might try warmer plugs with the richer idle. This is a 4 corner idle setup-front screws are out a little over 1/2 turn while the rears are exactly a 1/2 turn. 

[Chryco Psycho]

ok so you are close with the setting you are running , if idle quality improves richer that is where you want to be jetting is different best tested running at steady spped for 10 mins or more , shut off & coast to a stop & check a plug

[Strawdawg]

and, you may well be right.  If the float levels are correct as you say, then it may be too much heat boiling the gas out at time.  Other than blocking the heat passage in the heads and using a good insulator under the carb, the only other suggestion is to be sure your fuel line is insulated in the area around the headers in particular.

[bennydodge]

I also thought I was close before lol. No heat crossover(eddy heads), air gap intake-insulator under the carb as well. It's never had overheating or vapor lock issues either. Big cam as well so I think it likes a little richer idle.

[Chryco Psycho]

Did you install a lower rated Power valve to make sure it stays closed at idle in gear , often the PV can stay open & cause a rich situation with bad idle when you have a big cam & lower vacuum ?

[bennydodge]

Yep, PV's are good. Out of the box- primary side 4.5"/secondary side 3.5". Engine pulls 6" of vacuum in drive.

[Strawdawg]

It seems that you have covered the bases well so the only thing that I can think of is what Chryco has been on the trail of and that is something wrong with the fuel mixture that is causing it to overheat.  What do the plugs look like after you have been at an extended cruise?