When I converted my Stihl 62cc chain saw engine, I had to make a special intake manifold adapter out of aluminum. I then used a phenolic spacer to isolate the carb, but the carb screws still screwed right into the aluminum adapter. I had all kinds of running and tuning problems. So I made another phenolic adapter that had the carb screws thread into it instead of into the aluminum adapter. Then it worked perfectly. The carb mounting screws were transmitting enough heat to the carb to cause the problems.

AV8TOR