Making power out of the 318
In my experience the 289 K motor was the best all around. I never had any experience with a Boss 302. I do have experience with 351 Cleveland 4 barrel heads, Wow!
The 4V Boss heads from 1970 were better than the 1969. Ford reduced the intake valve diameter a bit to aid low speed torque. The Boss engines were a bit soggy on low RPM but came on strong as the revs climbed.
Heads on the K code 289's shared the castings with the other 289 engines. They did have screwin rocker studs for the solid flat tappet camshaft used. Ports are small with a dogleg around the pushrod. They also do not generate an abundence of swirl.
Like a number of teen heads with restricted port volumn from the factory, some judiscious porting can vastly increase the effectivness of the heads by a lot. A big flow number is not the solution to big power gains. Flow velocity which is a contributor to port energy has a big contribution to cylinder filling and swirl.
Now closed chamber heads for the 318 would aid compression and mixture motion. A person with some welding experience could build a furnace to heat a head to cherry red and weld up a quench pad into the chambers. Then it needs to be cooled slowly over a number of days.
Back in the 1940s to the 1960s, Chevy guys would do that to the 216 and 235 6 cylinder heads to raise compression as far as 12:1. Of course guides must be checked and possibly replaced after and then a complete valve job after grinding the combustion chambers to.conform to the new shape and volumn. Then the head surface needs to be milled for gasket seal.
I see minimal difficulty doing that to 318 heads to raise compression and gain mixture motion which prevents detonation. A little pocket porting and port matching with a carbide burr and you could have decent heads. Lots of time but minimal cash outlay involved.
