Theories?

Topic: Theories? (Read 1498 times) previous topic - next topic

Theories?

October 30, 2006, 11:45:15 PM

Getting tired of posting about this but....ever since my new manifold and used Holley went on I haven't been able to get the car to idle quite right. The symptoms are these: The car idles up and down rythmically and it gets worse the more it warms up, to the point of stalling if I don't keep the gas on; when I hit the gas pedal to accelerate the car bogs big time and almost stalls just from that. These are the possible causes I can investigate:

1. The float level. I never could get the fuel level up to the bottom edge of the sight plug. It's the same in the rear bowl. It's been suggested that I remove the bowl to mess with the float directly and I may end up doing that.

2. The fuel filter I currently have installed is a "stock for something" inline beer keg filter that was likely designed for a fuel injected vehicle and hence high fuel pressure. I kinda wonder if it's a restriction. I originally had a see-through re-usable filter but it was and I'm lucky I didn't blow myself up with it.

3. The timing. I swapped the manifold without touching the distributor so base timing is still about 13 degrees. But my old carburetor's "ported" vacuum port actually supplied quite a bit of advance at idle, maybe it was even full manifold, I can't quite remember but I'd wager the Holley's port supplies little if any vacuum at idle. I wonder if hooking it to full manifold might help.

4. I also have a messed up positive bat cable that I'm about to replace. It's loose but the car starts just fine so I tend to think that's not it.

5. Oh and one latch on my HEI cap won't engage because it strikes one of the manifold runners but I think the cap is plenty secure.

Bit of a long read I know but I'd appreciate any advice.

Theories?

Reply #1 – October 31, 2006, 05:17:51 AM

Id check 1&2 first the fuel filter should be quick so do it first but willing to bet #1 your float.

Theories?

Reply #2 – October 31, 2006, 10:52:16 PM

if it gets worse as the engine warms up would be confusing. Id also check the intake bolts as well just for the helavit

Theories?

Reply #3 – October 31, 2006, 11:14:42 PM

Check for a vaccum leak, maybe a crack base plate.

Theories?

Reply #4 – October 31, 2006, 11:56:26 PM

Hmm. I know you're supposed to retorque the manifold after the first run. Would that apply to the carb studs too?

I looked into fuel filters more and the important difference between carbureted filters and injected filters is the latter has denser filtration so in fact the one I have probably is restricting the fuel flow to an extent. Conceivably just enough to let the float bowl run lower and lower as the engine runs. Me and my crackpot ideas. I'll replace that filter though.

Theories?

Reply #5 – November 01, 2006, 12:00:47 AM

no,, your right,, im just a little left perse'. As the engine heats up, that heat transfers to the carb. Some adverse effect of heat may effect the floats as well. Its just an after thought to check the intake. sounds like its wanting you to force feed it when shes warm.

Theories?

Reply #6 – November 01, 2006, 12:11:41 AM

now,, speaking of the holley and my past and recent experience with the 750 street avenger,, i have to ask you if you were able to adjust the floats. were you ever able to get the fuel leve in the sight glass to adjust? if not, someone has the screw back out to far and the floats are not doing a darn thing for you. My symptoms were only noticeable during idle as well but we just thought it was because of the wolverine cam. this problem was only discovered after an eldebrock 600 something was put on and we removed the front and rear holly float covers and found the floats were not even connected.

Did you adjust your choke pully off assembly when the motor was BONE COLD?

Theories?

Reply #7 – November 01, 2006, 08:17:23 AM

As a matter of fact I turned the adjustment nuts this way and that to no end but the float always seemed to stay where it was. Oh here's a tidbit, the moron I bought it from shipped the carb upside down in a box that was too small. Could the trauma of shipping have disconnected the floats?

Theories?

Reply #8 – November 01, 2006, 04:39:41 PM

Sure it could have.

Floats are really delicate and the connection could be bent so that the float is never able to get to proper float level. Just have to take the bowls off to see.

Also, if you have a way to temporarily bypass the fuel filter, try that as well. Or just get a proper cheapie FF from the parts store for a carb. Shouldn't even cost five bucks.

As stated, check for vacuum leaks too. The surging may be from going between rich to lean, and the carb's choke action is supplying enough fuel to mask some of the problem - until the engine warms out of the choke temperature range.

Word of advice - don't buy an unknown carb. It WILL have problems, guaranteed. Ever heard of anyone getting rid of a perfect-running Holley? Or giving one to a friend?

Neither have I.

Theories?

Reply #9 – November 01, 2006, 06:13:38 PM

Quote from: 46Tbird;111145

Word of advice - don't buy an unknown carb. It WILL have problems, guaranteed. Ever heard of anyone getting rid of a perfect-running Holley? Or giving one to a friend?

Yeah I've already resolved to never buy a used carb again unless I'm planning to rebuild it.

If it is a vacuum leak it would likely be in the manifold seal and I don't even want to think about that right now. Since I have plenty of reason to suspect the floats I'm going after them first. I'll take off the primary bowl tonight and see what's what. If I can get away without buying new parts then great but at this point I'll do anything to make the car happy. It's cold outside.

Theories?

Reply #10 – November 01, 2006, 06:25:46 PM

Good luck man.

An easy way to find if it's a gasket seal is to spray a liquid (WD-40 will work but it will stink - try Simple Green or car wash soap) over the surfaces and see if it runs any different.

Or it could be the carb itself. Take a look at the jets, make sure they're not clogged or something, although that shouldn't affect the idle. But when your float level is screwy, it could be anything. :D

Just a question, do you know someone with a "good" running carb that would let you try it out? Also keep in mind that Holleys generally HATE cold weather. :o At least that's been my experience. Be sure to get it insulated, with full snug-fitting air cleaner and functional heat riser off the exhaust manifold. It will love you.

Theories?

Reply #11 – November 01, 2006, 11:34:35 PM

Well I disassembled the float bowl. Made one discovery off the bat, the needle and seat were screwed in so far that the adjustment nut wasn't even catching it anymore. Explains why turning the nut didn't do anything. No damage it seems. One other point of concern is a little patch of corrosion on the wall of the bowl. I've read about this happening in a particular run of Street Avengers but mine didn't fall within the date code for that. Maybe a result of being stored somewhere awhile. Either way it doesn't look serious, I'll chip off the loose flakes and consider it good.