Oh, I also believe the small ports of the D 64 intake helps, those are small 273/318 ports but seals fine on the 360 308 heads I am using. I use the Fel Pro print o seal intake gaskets, the ones with a steel core so the gaskets don't split. I drilled a 1/4 inch hole for the intake exhaust heat since its cool more often then hot outside around here Even in the summer the nights are 60's degrees or cooler. I found a heated intake is a help up here..the carbs seem to stay cool