73 318 will J heads work???

Unless you are 1. turbocharging, 2. supercharging, or 3. willing to part with a lot of cash for some custom made pop-up pistons, I don't think J heads will improve the output of a 318 BECAUSE.... the combustion chamber is too big and will lower your compresssion ratio to a point that it's really detrimental to cylinder pressure.

Those heads would work great with a blower, though...

Might consider a Vortech, Procharger, Paxton, or Powerdyne unit. Not a cheap way to go, but adding power in significant amounts is never cheap or easy.

A centrifugal blower setup will usually add about 100 hp and run on pump gas if you add an alky injector to stave off detonation.

Just a thought.

Failing that, the heads with a casting number ending in "302" seem to be the best choice for a mild 318 street build. They're cheap at junkyards and on a lot of mid-'80s 318s.

Good luck!!!

Bill, in Conway, Arkansas