Hello,

I have a rebuilt flattop 327 with a new holley 600 and elderbrock aluminum heads. The car ran perfect until the other day when it stalled at a light. It was difficult but I did get it started and it drove strong on the way home. I checked all of the vacuum lines, fuel lines, and bolts to be sure there were no leaks. I looked down into the new carb and could see the jets spray gas when I moved the linkage. I checked the plugs and wires and all are fine. I did see a small amount of oil residue in the air cleaner that was never there before. The car will right start up when it is cold but seems to build up quickly and stall even in park or neutral. I recently had the power glide swapped for a new TH350 and even checked the vacuum lines from the transmission. The engine does not make any tapping or strange noises. Can anyone point me to a possible cause.

When you say build up quickly do you mean load up rich at idle.I f that's the case you might have a spec of dirt in the needle valve or your float could be porous or out of adjustment . I would look at the first one . To clear start the car and with a small and I mean small rhythmically tap the fuel bowl while revving the engine up and down. This will usually clear the needle and seat unless you have a boulder in there LOL .If that works change the gas filter .Alex

When I say build-up I mean load up and the car will slowly stall. It takes about 1 minute after I start the engine. It certainly makes sense that there could be dirt in the needle and seat. The question is why would it start up fine and run fine when i'm driving on the open highway? Is there a chance the fuel pump could be going bad? Thanks for your time and expertise.

Is your choke butterfly opening up all the way as the engine warms up?

If not, that would cause it to run excessively rich.

check your fuel levels. To high of a fuel level will cause this (just happened to me!). Ethanol residue can gum up the carb. Suggest opening it up and cleaning it.

The new holley is a vacuum secondary with electric choke. It has less than 300 miles on it but I suppose it could have sucked up some gunk. I will remove the carb, clean it thoroughly and re-install. Thanks for your help. Larry

its the ethanol film. I rebuilt my qjet less than 50 miles ago. Took it for a ride on Friday and float was glued to the bowl and a piece of film in the jet. The gas evaporates and creates the film.

Maybe a pin hole in the float.

Good idea to double check your float level as others have suggested.
Next you need to re-adjust your idle mixture screws. They could be set too rich. As a base-line run them in (clockwise=leaner) until they bottom out (do not use very much force), then turn them back out (counterclockwise=richer) approx. 1.5 turns. Use a vacuum gauge to tune your idle mixture for the leanest setting that will pull the highest vacuum at idle. while idling with the vac gauge connected, turn each idle mixture screw out 1/4 to 1/2 turn at a time and let the idle stabilize again. Continue to richen the idle mixture slowly until you find max vacuum reading. Going too rich will cause the idle quality to degrade so then turn back lean to find that sweet spot.

600cfm may be a bit too much for a 327. You may try dropping down a jet size or two on the primary side.

Distributor lockdown bolt tight so that disti can't retard?
Other than that, fuel bowl level would be my guess.

My holly 650 would just flood itself when I got my car back from restoration, it would be fine when driving but would stall whenever you let up on the gas.

Holly's are supposed to be prone to needle/seat problems so I removed and cleaned both needles/seats and it hasn't happened since.

Be careful to note how many threads are showing on your needle before removing it because it sets your float level.

Once you remove the top retaining screw, the small nut/cap that goes over the top of the needle just pops up, don't turn it or you will change your float level.

Very common after a rebuild to get a bit of crap go thru and jamb in the float needles.. a small bit will not be noticed under normal driving, then idle and within a few seconds idles rough , if left will stall. A larger bit will drive fine , go to idle will cut out....even bigger bit will notice at low speed cruise... will not idle.
Also VERY COMMON after a rebuild and NOT done
When a carb, even out of the box is put on, the float levels NEED to be set. The accelerator pump gap checked and re set... NEEDS mixture and idle speed screw set to factory 1 1/2 turns and the secondary butterflies correctly set while running... with the idle timing in ball park.

All of the above are the basics of basics must do stuff... and the most common of faults will not idle right , has a bog, etc

Everything Steps says is correct. My bet is on the fuel being high whether by adjustment or by crud in the needle and seat. do you smell it going rich and see dark smoke when it stalls?

Spray out the idle air bleeds, preferably with air, or brake cleaner before doing anything, as it is the easiest. New carbs often have casting flash and chips inside, demons were the worst.

How is the tank? Is it full of crud or rust? Fine rust will get through any fuel filter and eventually muck up your carb. Ask me how I know.