Hello Charlie,
I have moderately hopped up GMC 302 in a 1940 Chevy which has been on the road and sometimes race over 22 years. It still runs great. The 302 head is different from the smaller engine heads. All 302 head intake port ring outer diameters are 1 3/4 inches. I think the 270 H heads are also 1 3/4. All the other smaller engines have smaller intake ports and smaller valves. Ported heads are usually enlarge to the 1 3/4 inch outer port ring diameter and larger Chevy V8 valves are installed. My head has been ported.
