Originally Posted by 69elko
Why don't you put some good aftermarket heads on it? That will really wake up the engine. Put some gears and stall converter also. The 400 has a 8.0 to 1 stock compression ratio with the 76cc heads. If you go to a aftermarket head with a 64cc chamber, you will raise the compression to about 9.0 to 1 which will suite the cam you have now. That alone can raise about 20 horsepower. You can expect at least a 60 horsepower gain from changing heads. Just remember to have the steam holes drilled in the heads before you use them.