1998 Cobra short block vs, 2008 Mustang GT short block

[Foghorn]

Initially posted this in the S-197 section, but didn't get any traction. Reposting here - mods please move to the right forum, if there is a "right" one.

I have purchased a 2008 Mustang Bullitt with a locked-up engine. The car has 117,xxx miles on it.

I have two 32v 4.6s just sitting around taking up space: a 1998 Cobra engine with about 600 hrs. on it (actual mileage unknown), and a 1995 Lincoln Mark VIII engine with approximately 100k miles.

My thought is to swap the 3v heads (with appropriate maintenance) and front dress on to one of the 4v shortblocks. This will be a DD type car with an occasional HPDE after appropriate suspension upgrades.

Any thoughts for or against? Any major differences btwn the blocks that would prevent this from being a "hand-tool" type evolution?

Thanks in advance!

 

[5.0 Hatch]

I believe all modular heads bolt to all modular blocks, however, the pistons between the variations are different resulting in undesired compression ratios depending on the combination.

 

[Foghorn]

Thanks! I had not considered that aspect of swapping the heads.

Searching the forums shows that both the B style 4V head and the 3V head have 52cc combustion chambers.

The OE pistons on the 3V are 6cc dished while the OE Cobra pistons are 3cc dished, which would bump the compression up a bit...haven't done the math yet, but thicker head gaskets could mitigate the difference of 3cc.

I did see a forum post that stated flat top pistons would yield 10.85:1...