yet another 3.0 8V question
 

I continue to contemplate my options for upfitting the 90 S2. I still have access to a nice 2.7 liter engine and it continues to tempt me. Putting aside thoughts of forced induction:

I recognize that maybe nobody has done it, but, here's my latest thought: can I bolt the 8V head right up to the S2 short block without any radical change in compression ratio? If it stays about the same, I will of course give up a little power vs. the 16V head, but I am in need of a valve job anyway so the 16V head has got to come off. This would be a good cost-effective way to keep myself on the road, since a 16V rebuild is not in the budget these days. I would of course have to deal with changing the DME etc, which I have from the 2.7. TIA SG

Hmm, access to a 2.7L engine?... If you don't take it, what's it selling for?
I have been bitten by the turbo bug, and am planning on building a 3.0L 8V turbo monster. 16V heads scare me =) Although, if I got a free/extremely cheap 16V head, I would make a 16V 3.0L turbo.

I believe the 8V head will _not_ bolt up to the S2 block, I believe there are some small differences in the water passages (correct me if I am wrong), however there are shops out there who will do the head-work to make it fit.
It will not breathe as well at the 16V head will, so you will lose some power (which you do understand). If you're keeping the displacement at 3.0L, I don't think you need to change the DME, you would see more of a performance hit by using the 2.7L DME than the 3.0L. Although, FR-Wilk is probably the guy to answer that question.

Why would you want to do all that work to take a step backwards?

zero - The 8 valve 2.7 head is different than the 2.5 head; since the short blocks are essentially the same between the 2.7 and 3.0 engines, their heads have the same water passages.

tifo - I don't see it as a step back. The 16 valve cars are a little too complex for me for the power realized. I'll take a few fewer horses, with the upside of better 8 valve reliability, and for cheap for me vs. paying 2 or 3k for a new 16 valve head, not to mention uniqueness. And it's really not a lot of work - R&R a head is a weekend project, AND I've got to do it anyway (likely bent valves).

I believe someone calculated a 2.7L (2v) head on a on a 3.0L (4v) block would yield a c/r of about 9.1

should not take very much machine shop work to get it down to 8 or 8.5 if you had any forced induction in mind

Oops, my mistake, Yep, the 2.7L block is essentially the same as the 3.0L, I had a brain fart there.

I as well dislike the 16V head, chain tensioners, pads, 2 cams, etc... too many things to go wrong. Especially if you're going the forced induction route.

If the 2.7L head on the 3.0L block will yield that low of a compression ratio, then they must have changed rods or pistons between the 2.7L and the 3.0L?

3.0L pistons are shorter than the 2.7L pistons, have 4-valve reliefs rather than 2 and a different 'squish' design...but should work with the 2.7L head

I believe the rods are still 150mm…no change

I thought it would be the pistons that were different =)