Backfire and stop running

I looked for a vacuum port this morning but doesn't have one. I'll start checking all the electrical connections. Thanks
 
A too lean mixture will create those symptoms. You have gone through 3 carbs so it's not a carb problem. The GAV will provide a lean and a rich mixture. Have you checked the mechanics of your GAV to make sure it's functioning properly?
Good luck.
 
The GAV stands for gas adjustment valve it's on the choke rod you rotate it counterclockwise to rich in the mixture clockwise to lean it out when the engines warmed up it should be open roughly 1⁄4 turned or slightly less.
 
Our coupe had a carb that I cleaned up and put on the car. It would start, run 30 seconds and backfire and quit. After sitting for 24 hours, I turned the gas on and stuck my middle finger into the carb and felt for fuel around and on the cap and main jets base. Eventually leveled the lower half on the work bench and filled the bowl with fuel. After a few minutes the jets were leaking at their bases. I switched to Bratton's black gaskets (some form of plastic????) and the problem was solved.

I've read that some smooth the bottom of the hole where the gaskets reside. I'm not sure what tool they use for that or how the keep it straight. Others use a small coat of fuel resistant gasket sealer on the faces of the gaskets.
 
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47topless said:
My monies' on nkaminar, and his lack of fuel flow theory. A while back, I was having the same symptoms, and he suggested a "lean" mixture was the problem. Mine was due to a crap filled gas tank that resulted in a clogged fuel flow filter valve that severely restricted gas getting down to the carb. It would start, backfire and quit.
rkaminar also gave me a wonderful tutorial on the function of the GAV. Priceless!
Good luck with yours.
Click to expand...

Yes, him and a lot of other guys on this site are very knowledgeable on these cars. When I have a problem this is where I come too.
 
I installed the "Zipper" distributor on my 30 Tudor and experienced a similar problem. With the old stock distributor it started and ran best really lean with the GAV completely closed. Zero backfires on start. For the first few weeks after the Zipper installation I had a lot of popping and occasionally even stalls on cold starts. It would even out after 30 seconds or so. I eventually increased the GAV mix to about a half turn and it almost completely eliminated the problem.
 
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