Pre chamber inserts and CR

[DA BIG ONE]

A GM training manual published in 2002 states: "the shape and size of the insert is specific to each 6.5 diesel engine and is key factor in determining compression ratio".

Are the pre chamber inserts different in 1999+ heads, or? I see information in feature articles about inserts but it's showing only one insert type for the 6.5td.

[More Power]

The port size and shape used by a precup may affect compression ratio, but only slightly, and only when going from a small port cup to a large port cup.

They may have meant the cups are more application specific. High load NA military spec cups are a little different than civilian NA cups, and there is a larger difference between NA and turbo cups. I believe it's important to ensure the heads incorporate a matched set of whatever. Mixing and matching cups and/or head casting numbers wouldn't be a good idea.

Jim