The 454 that I just put in the Chevelle has a strange (at least to me) problem. When it's cold it starts up great, then as it heats up it runs progressively worse, by the time it reaches 190 degrees it hardly runs, and even has backfired through the carb a couple of times. Where do I start troubleshooting this? :(

Originally posted by gatkins:
Where do I start troubleshooting this? :( I'd start at the carb and then go to the ignition.
Kid

I've had an idea.....I have a 190 degree thermostat, but my electric fans come on at 180 degrees. My car struggles to get to 190 degrees, what do you think the possibilities that it's heating up to 180 degrees, and never reaching 190 degrees so the thermostat isn't opening, which causes the intake to stay HOT and vaporize the fuel???? I guess this might not be possible unless there's air in the cooling system, but this is what it feels like as it runs.

I'd start deeper, valve lash, and then work out to ignition , then carb.

BTW, HEI with module? Then replace the module first. Coils can do wierd things like this too. 12v hot to the HEI? If you;re using the resistance wire, it might be giving too little voltage. Check voltage at coil when its hot and running crappy.

Sounds like the choke is stuck closed to me???