I bought a 31 Cabriolet 68-B and have been having a tough time curing a carb backfire problem. I discovered this engine looks slightly different from other As as the oil return line is missing and it has a fuel pump port with a cover plate on the block. Looking through some old hand written records that came with the car I see the note "Russian motor from Long Beach". The block has no engine number stamped on it, the plate completely is blank. The head says USA and has standard size 7/8 spark plug holes, not metric like the GAZ head.
How do I confirm my suspicion of having a GAZ B Motor? If someone later installed a standard "A" head on it would that work? It idles well but continues to backfire out the carb when trying to rev over about 2200rpm and acts like it's runnning lean unless I really open the GAV a few turns. I've verified free flowing fuel, timing is spot on and spark is good. It also has a Zenith 1 carb and I read the Zenith carb for a B engine is bigger so if I have a B block can it run with A parts (head/carb/Dist)? Here's a pic (ignore the large plug in the vacuum port). Is a GAZ B more valuable since it's so rare?
Thanks for your help!
