Just machine the 2.5L heads to look more like the 3L head. I have already done this to my cylinder heads and I calculate a reduction in compression. I went for about 10.5:1 If you wanted you could safely go down to the 10:1 that is the same as the 3L. I've already examined both heads in detail and they are from the same casting with some minor changes. The 3L chambers are just a little bigger around the valves (unshrouded) and that gives them the proper compression ratio. It took all of 45 minutes to machine my heads with a carbide bit and die grinder. Then I finished with a light hand sanding to get the same finish.
Same benefits of the 3.0 heads, but with waterpump and cams all stock.
Of course if you don't trust what I did, I do have two brand new 3L heads, cams, and valvetrain components MINUS the valves, for sale.
I might even give up the the timing chains, sprockets, guides, oil pan, valve covers, etc. for one LOW price.
I will swear to the fact that these engine parts have almost no miles on them.
warmonger
