Motor runs better below full temp

[Gas Pig]

My 302 with a fresh Q-jet carb seems to run a bit stronger or crisply when not a full temp. So, I’ll first take it out it seems to pull harder but as I drive it long enough the motor seems to go kind of flat. The only thing that seems to be a constant is the temp. I have the stock 180 degree thermostat and according to the gauge it’s right around 190-195. Some say that’s fine, but I have always in the past put a cooler 170 or 160 degree thermostats in my trucks but this motor already had the 180 in it.

Me thinks that she might be lean since when it not full warmed up the choke is on. I’m going to pull a plug and take a look but is there anything else I might be overlooking?

Thanks Jeff

 

[DirtDonk]

I’d say you’re on the right track initially. I would call it running lean as well.
Have you checked for any vacuum leaks yet?
Do you have the PCV system hooked up, and with the correct valve for your engine?
Any other vacuum accessories?

I suppose you could narrow things down by holding the choke all the way open and driving it around even while the engine is cold.
That way you could determine if it’s mixture related and not some other kind of temperature related thing. Although I can’t think of anything else, other than the choke that would be temperature rated related.