Power loss. 318 Vs 340 manifolds

Make a template of the 340 heads and lay in over the 318 manifolds, do some grinding to not shroud the ports on the 340 heads with the small 318 factory manifolds. Also measure the outlet of the 318 manifolds, if it real small outlet, open that area up a bit also. I bet doing those two things it would make the 318 manifolds that much closer to the factory 340 manifolds.

Mark Lelchook
Performance Welding
Racing Headers
perfweldheaders.com