Can someone help me id a set of PI heads. My father in law swears the heads on the 390 he gave me are PI heads. When I checked for the HP thats supposed to be on them all I find is a small stamp that looks like a HD. Its not cast in the head like I thought it would be. Please help.

 

http://pliverman.home.mindspring.com/index2.htm

The above site lists many casting numbers. The only real diffence in a PI head may be the combustion chamber volume. The PI heads may have a bit smaller combustion chambers (about 60 cc verus 68 cc) for more compression ratio and taller intake ports, 2.34 inches verus 1.93 or so, but I've seem many that weren't taller. The final compression ratio depends a lot on the piston used

The things that really made an engine a PI were camshaft, carb and the exhaust manifolds. It's my opinion that the cam and exhaust manifolds were most of the PI's HP difference. The standard cam was low performance and the standard passenger car exhaust manifolds are shouldn't be used unless your swapping the 390 into a Ch*#ie (got to disguise the bad words.)

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 3.0, 5 speed, 3.73 posi