318 heads and combustion chamber size

You need to post more information for someone to help you.

What year is the 318 that you are working on?


What casting number heads do you have on it now?


From you mentioning about an air pump, I will assume it is a later 70's or 80's engine.

You can swap any year 273/318 head on there EXCEPT '64 & 65 year heads as they have different angle intake manifold bolts. So you can use any heads from 66 to mid 80's for sure (i'm not sure about the magnum heads).

If you do some research, I believe that the 66 or 67 heads may have smaller combustion chambers that what you are running which may help your compression. As far as hardened exhaust valve seats, you can have any head machining shop install them so you can run pump (nonleaded) gas.


You can also have the heads improved by porting the heads and also if you wish, have the 360 valves installed if you have the valve jobs done and hardened seats put in. A little porting and some larger valves can wake up a 318.

Also I recommend using matched sets of heads with the same casting numbers, don't just buy one that doesn't match the other side casting number to keep everything even.