Idles down and dies

My new engine build is done and was running perfect for a while, running on 110 it would start up and idle fine at 1,000-1,500 rpms. Sitting there at idle for a while it only got to 195 and never went higher. I tried running it on E85 and tuning it and thought maybe that was the problem but it's back on 110 and still persisting. I have been tuning off my wideband O2, AFR's look perfect at idle.

It used to just be that once in gear and sitting at a light it would eventually work its way down and die, now it will die in park if the idle isn't set at 1,500 or 2,000. And in gear it goes down right away. Checked the floats and fuel pressure, air bleeds, jets, transfer slots, even drilled the throttle plates at one point which made it more finicky, adjusted idle mixture screws (idles higher when turned to lean it out), checked timing as well. It acts like I shut the fuel off and it runs itself out of fuel. Also, it now will get HOT and try to overheat. Could a vacuum leak cause this? My carb gasket was torn and crappy when it ran fine, and now it has a gasket I made from the black gasket material you can buy at the parts store. I do not have another dominator style carb to bolt on as a test, maybe I should be looking into a newer carb? Or could it be something else?

Sounds like a vacuum leak to me what all is hooked up that needs vacuum

Nothing, no vacuum ports on the carb either. I had a vacuum gauge hooked up with the old manifold but with the new one I'd have to put the spacer on with a fitting. There is nothing using vacuum so my guess would be the carb gasket or around the ports as the only place for it to leak. Unless maybe the carb gaskets aren't sealing because I've had the metering blocks off so many times recently?

Intake might be leaking but if you had the carb apart that many times buy a kit and rebuild it and let it soak real good before you put it back together

Hey neighbor,
Some of the intake gasket materials tend to creep and lose compression. You may need to re tighten the imtake bolts. Try snugging them up and see how much they need to turn.
if the mixture screwss are turned all the way in for best idle there is a problem.
What is the timimg at with the idle.

Holley carb? Transfer slots uncovered?  

maverick wrote:Holley carb?  Transfer slots uncovered?  

Correct transfer slot measurement, should be around .040" or the transfer slot will roughly look like a "square" hole when .040" is acheived.

Trash on your needle and seat?

Thing is all over the map, it will idle UP if I turn it up to far but idle DOWN if it's any less. I have set the transfer slots multiple times, lowered the float level, adjusted the idle mixture screws OUT and it idles up now. I checked the primary needle and seat which looks good.

Today I'm going to tighten the intake, maybe change the carb base gasket, and change the metering block gaskets. Maybe also check the carb body and blocks for straightness as well. My intake gaskets are the Cometics, I used some Right Stuff RTV around the backside to hold it in place and seal. The top I left alone because it has the blue rings around the ports.

New carb still does it, better, but still. I'm thinking the big cam isn't pulling fuel down low or it may need more timing. maybe a 4 hole carb spacer or locked out timing is in order. Also breaking up at 4k, I think the weights and jumping around at that rpm. It has the stiff springs in it.

bb429power wrote:New carb still does it, better, but still. I'm thinking the big cam isn't pulling fuel down low or it may need more timing. maybe a 4 hole carb spacer or locked out timing is in order. Also breaking up at 4k, I think the weights and jumping around at that rpm. It has the stiff springs in it.

I think you got a intake leak or valves not adjusted correct check your valve lash and make sure they are set correct.

How much initial timing do you use? How much total? Locking the timing will make it less finicky but you may need a start retard.

Idle mixture screws - out is richer. How many turns out are you at? When its idling can you see fuel dripping from the boosters?

Suckin air somewhere  

Right now I have a different carb on it, with the timing locked out at 32 and both idle adjustment screws all the way out it's up at 1500-2000. The timing really made it want to idle high, everything runs great. I will be pulling the intake at some point though for a port match job and I'll seal it better too. Car got into high 10's without any jetting changes, pulling the tires about 8" max

If it won't idle lower than that, it's getting air from somewhere it shouldn't.

You could take a can of spray lube or something similar.... Spray a little around the carb while it's running, and also do the same down the intake gaskets.  If you have a leak, you will see it get sucked right in.

Have you tried adjusting the secindaries?

the O/P said in his first post that it was on e-85 and then switched back to race gas, E-85 is rough on intake gaskets when intake is not tightened good from the start, my thought is the intake gaskets are leaking and need to be replaced, I know this because I've been running E-85 for 5 years now and have had to change a few intake gaskets. Very Happy