Originally Posted by 52Carl
Don't they both have the same 848 head?

Look again- - - -these are TRUCK engines- - - -none of them are listed with 848 heads, which were used on passenger car 235's. Anything that raises 235 compression will make noticeably more difference on a 261 which has 26 cubic inches more displacement, or a little over 4 cubic inches per cylinder. That's 66 more CC's of cylinder volume being stuffed into the smaller combustion chamber. If a thin steel or copper head gasket is also used, the compression gets another bump.

848's are the highest compression(smallest combustion chamber) stovebolt heads available, equivalent to shaving .100" off the earlier head. It makes a noticeable difference in performance, especially if it's combined with some valve work and a big overbore. Drilling the "steam" holes makes it compatible with the Siamesed cylinder walls of the 261 engine.
Jerry

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