Guys and Gals; I have a question that I haven't seen on here in a while, and I am at a point where I need some guidance. I have a blown head gasket in my 302, which is a '75 vintage engine, rebuilt with 30K miles on it. It has 1966 289 heads. I have the stock heads, and need to know if I should put the stock heads back on them, with the 302 non-rail rockers from the 289 heads, or leave the 289 heads on the engine? I have heard the 289 heads hurt performance, but not actually sure. Any and all help will be of help. Thanks,
The rail type rockers have a rail to act as the guide to keep the rockers on the valve. The 2 different setups are not compatable.
If you don't have rails on your rockers, you have to have another guide method setup on the pushrod side to keep the rocker on the valve. (pushrod guide plates)
So I wouldn't switch rockers from one head to another, because you could end up with nothing keeping your rockers squared up with your valves or nothing to keep your pushrods from gouging themselves to death... right into you oil pan.
BTW: The 289 heads will run slightly higher compression, so performance-wise it is better. Otherwise, there will be little if any performance difference between heads.
Another concern... Have the 289 head been fitted with hardend valve seats? It was designed for leaded fuel, and didn't come with them, but to run 289 heads with unleaded fuel you need to install hardend seats.
Dave; thanks for the reply and the information. I think the stock heads will be the better bet, since it is a stone stock engine and not raced. I am just going to have them checked for flatness and stick them on. Thanks a bunch,