Backfiring issue

davidcribbs said

I have put the old carb back on as well, since I agree, this may have been the issue. That did not help either.

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I'm of the school of kiss... On these cars it's always something simple....
Only way it could really be something catastrophic is if it has to do with the cam or the valves... Like not putting oil with zinc in it and starting to wear things out over the last 8 years?...