Bob
This is another internet myth, there's hundreds of smaller cubic engines with 250cc + ports that will rip your head off when you step on the pedal. I know I built a few. It all comes to proper camshaft and carburetor and tuning.
Good advice. Port volume should be an essential part of your decision in planning and picking the head that Out of the box they were advertised at 215cc. They are probably more than that now. I replaced my 16 iron heads on my 400 and they killed my low end. I didn't know about the "lazy" air charge due to the port size. Apparently they would require a much bigger cid to get the full potential from them. Don't get me wrong, they still run fine but for a 98% street car it can be sort of disappointing when you can't spin the tires at will like you could before. Planning and knowing is everything before you buy.
