318 cylinder head

toolmanmike said
A 340/360 head will drop compression about a half point. The bigger ports can help with flow but you need a bigger cam and some careful tuning to make it work and benefit you.

David Eldridge said
Ok I know there are a ton of posts like this, but all seem to go off topic. I'm sure this will like all others but worth a shot. I have a 1970 Dodge Dart with its original bone stock 318 with a 4 barrel. Heads finally need redone. Question is will 340/360 heads or an aftermarket head drop the compression ratio too much? Once again I know this has already been asked but it seems it's with all the super low compression 318's from the mid 70's. I'm not in that boat. And no no engine swap or pistons or anything. This is the original engine to the car and the bottom end is great! Might do a mild cam too.

If you have the idea to change heads why not go with a 66-67 273 head (#178,234 or 920 or late 80's #302's) and bump your compression up a half point, add a little cam and with your 4 barrel it will be a nice combination. It's a lot of work for a little bump in compression though and no improvement in flow. Or do something different and go like AJ suggests and add a converter and or gears.