2.7L vs 2.5L is it worth the difference?

[Chuckcruzin1986]

I am finding hard to find a 2.7 short block to build (new oversized
pistons, honed etc) for my turbo M20 engine.
It seems I can find more 2.5L used engines.

Should I keep hunting for a 2.7?

Chuck

[kronus]

2.5 and 2.7 blocks are identical

[cleanasse30]

The 2.7i combo, assuming you are using an ETA bottom end and an I head, is pretty nice. I'm making 315hp/330ftlbs on my 2.7i with about 10-12lbs of boost (I have boost creep right now). You need to re-ring the pistons or you will run into the same oil burning issue that I have. From what I've read, the stock ETA rings can't handle the increased RPMs and have lots of blow by and oil burning.

[varg]

That's funny, 2.7s were far easier to find for me when I was searching for my 2.5. It's worth it if you do it right ('i' pistons, 'i' head, decked block), but if you just slap an 'i' head on a 2.7 bottom end you'll wind up with less than optimal squish in addition to the 8.4:1 compression ratio. Not a "bad" combo but you're not getting the most out of your 2.7 that way.

[shadowracer]

The biggest difference between the 2 that makes one a 2.7 and 2.5 is the stroke of the crank, and the connecting rod length as far as I know, I know pistons are different as well as the head I believe they have the same 84mm bore too, not sure if there is anything with the blocks. bottom end 75mm stroke (I crank) 81mm (e crank) and rods are 135mm (I) vs 130mm (e).

Myself I did an s52 crank, 1mm over bore on the block, 135mm rods with custom pistons for a 3.1L with boost added.....:devil: