Have a 1967 GTX 426 HEMI dual 4's. Idle's and starts good. Runs up to about 1800 to 2000 rpm and when trying to get any higher rpm the engine boogs and backfires out the intake. Reset both points to 27 degrees and total 38 degrees according to the book. Reset timing to 8 degrees and tried to checked total timing advance but could not get the engine to run good enough to check. The timing would advance when rpm was raised though. Rebuilt both carbs and checked for air leaks. Has good vaccumn and good compression. This engine was rebuilt and had been run for 500 miles then stored for 25 years. I replaced all seals and checked bearings and used a bore scope too check the heads for rust. I did not pull the heads because they looked good. The linkage to the carbs are set so the back or rear carb opens the throttle plate first so I assume the engine runs from idle to about 2000 rpm on the the rear carb, then opens the front carb with higher rpm. This is when the engine boogs and starts cutting out or poping out the carb. Where should I look next?
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