Cast manifold
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
The CJs got the big ports, but they also got a much better cam (same cam as the 390GT) and a big port intake and a bigger carb along with improved exhaust manifolds on top of the 38 extra CID and the .2" more stroke. It wasn't any one thing, but a combination of thing chosen to work together. I have the Ford Muscle Parts Books and in one of them they have a step by step parts change over for a 390 to 428CJ parts and also show the horsepower increases each item gives. Interesting stuff.
Needsmorecoffee.
Joined: Oct 2004
Posts: 3,624
Likes: 2
From: CT
There are quite a few of those old performance catalogs online at www.mustangtek.com hit the library link in the sidebar. Some interesting reading.
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Casting numbers and the angled exhaust manifold bolt holes. Chances of finding them in a yard are low. Look at Edelbrock or a number of other aftermarket suppliers, Blue Thunder, etc.
Needsmorecoffee.
Joined: Oct 2004
Posts: 3,624
Likes: 2
From: CT
Typical CJ head casting numbers are C8OE-6090-N. Those are the most commonly seen and found. A while back I was shopping for some for a friend and came across a very nice set of bare CJ heads for $400. The 69-70 CJ heads sometimes bring the big bucks for the numbers correct crowd. But there were service replacement CJ head castings made thru late 71 you can still find for decent money. Just be aware of the thumbprints, porting and repairs while shopping for a set. There is some junk out there.
