My 69 SS396 is running really good after my carb rebuild but last night ripping around downtown SF, i got in some bad stop-n-go traffic and the engine was getting up to 200 degrees (i have a water temp gauge) and it started to idle faster on it's own. around 400rpm higher! Then i would punch the accelerator to try to clear it and i got a pop (maybe backfire) from the carb. Then i could smell like a sort of gassy vapor from the driver seat.

Just wondering if i should lower the floats a bit and lean out the mixtures, or is it something else. It runs GREAT under normal temp of 160-180. No hessitation when punching the accelerator, no missing ever. Or should i just stay away from stop-n-go at all costs? Hahaha. Thanks......

If you have room you can add a heat shield under your carb. You probalby have seen them they are like a rectanglier shape piece of aluminum with a gasket already bounded to it.

Dave

Heat shield is the way to go as Dave stated, I installed one on my 427 last summer and it made a huge difference. Before adding the shield I couldn't touch the front bowl on my holley without burning my finger, after the installation I could rest my hand on it with no problem and that's after a long run on a hot summer day. You will need a spacer between the shield and carb for acc. pump clearance and you may need to alter your fuel feed line to the bowls. I used a special 1/4" thick gasket from Holley as a spacer and a regular gasket between the manifold and shield, it raised the aircleaner about 1/2" so check your clearance.
P.S. DON'T use a bunch of regular gaskets to make the spacer, I did because I was in a hurry and I ended up breaking off a corner of the carb-base..... :clonk:.....had to wait three weeks for a replacement from Holley....... USE THE SPACER .. :thumbsup:

This what it looks like,,

http://www.holley.com/HiOctn/ProdLine/Products/FMS/FMSCA/108-70.html

Thanks guys. Jim, were you getting popping backfires out of your carb at high heat? I mean, what is that? Is that the fuel getting so hot it is coming back out of the valves or what? And why the higher engine idling? I'm going to price out the Heat Shield and check it out. Thanks again...

No, I wasn't backfiring but the engine was running very rough and I couldn't get it to idle, this had happened several times this past summer. Since the heat shield I never had that problem again.......... a friend with a GTO had the same problem he told me that the gas in the bowls of the Holley was boiling at idle from the heat off the intake and causing the problem.