My Pete rebuild

[Rawze]

(12-27-2019 )tree98 Wrote:  What does the combustion chamber of the head look like compared to an OEM head (if you still have the old head) maybe that's where the compression ratio was changed?

the bottom of the head is flat. - However, recessed valves because the head was re-machined can change the compression ratio by quite a bit (lowering it).


Compression change would happen if that piston bowl design is different. I am also pretty sure that whatever aftermarket company that makes them, does not want to get sued for copying a piston design ... There has to be some differences, and that crown looks too tall for an ISX unless it is a small tier engine (the lower 400hp tier), or a 2350, but it is hard to tell in the pics.

Also the compression ratio can be changed by the TDC point of the piston (distance between wrist pin and crown) and/or the position of the top ring on the piston too.

an aftermarket or incorrect valve camshaft can significantly change the compression ratio too.