I have a 400 (1974) in my GTO. Holley carb, HEI ignition. The 2nd cylinder bfrom the front on the drivers side and the front cyclinder on the passangers side seem to be dead. Or at least the engine smoothness and speed does not change when you pull the plug wire off them at idle. The plugs are good (changed them with a cylinder that was hitting good) Plug wires good did the same as the plugs swithing them out. Has great spark, compariable compression to the cyclinders next to them. Valves are opening and closing properly and are adjusted correctly. Any ideas?

 

You won't ever know for sure unless you take a compression check. Try that. All cylinders should be at least within 10% of each other closer to 5% is better! Does the engine shake as the RPMs go up? Feel low on power? When was the last time the engine was rebuilt?

 

No substitute for basic mechanical tune-up knowledge- time to get under the hood and do a compression check.

BTW, what year is your Goat?

Geno