Help me, help me!
I'm confused. I have been told all of my adult life that the high compression cylinder head used on 235 engines ending in the casting number "848" was used from 1958 to 1962. Now, some one is telling me that head was also used in 1956 and 1957.
Can someone please verify the years the "848" heads were used?
Thank you!

Hi 6cylindersovertexas

Stay with me on this one and if you follow the instructions exactly you will get your answer.

Back out of this string and go down to TECH TALK. Enter Tech Talk, In the upper right you will see a pull-down menu. Pull it down. Select "Show all Topics". Press go. Now there will be many subject lines. Select "Casting Numbers". Scroll down approximately 7 pages and you will find Cylinder Heads. You will find among other things that the 848 head was for 1956.

(What is a 235 High Compression Head?)

The compression ratios of 235 heads were-

53-55=7.5 to 1

56-57= 8.00

58-62=8.25

The 848 heads began in 1956 and continued thru 1962 .Were also the parts replacement head going back to 1953.

The same casting was used from 1956 and up but a little more material was milled off of the surface to go up from the 8.00 ratio to the 8.25 in 1958.Your goal would be to find an 848 head with a 1958 or newer casting date.The 8.25 was the highest C.R. head used and was designed for use with regular grade fuel.

I assume that was Regular grade LEADED fuel?
I have a 848 head that is off of a 56 1/2 ton truck.
Since it is also a replacement head for a 53 would milling the 53 original head be equal to a 848 head, or is the combustion chamber smaller in the 848?
What is the compression ratio for a 1957 261 engine?

The C.R for a 1957 261 was 7.8 to 1...Raised to 8.00 to 1 in 1958 and that was its max,

The 261 was designed to run on regular fuel-would equal about 85 octane by todays rating.Leaded was never specified for any car-only minimum octane number.Lead was never required for use in an engine - only after its removal some said it was necessary to "lubricate" valve seats.This has proved to be false by most engine rebuilders today.Have run unleadded for years in my old cars-driven them at high speeds -under load-etc. with no problem.

The combustion chamber was the same from 1953 and up-the 1953 head would require milling of about .060" to raise from 7.5 to 8.0--inlet valves would need to be recessed plus a few other minor changes.Sure you would never feel a gain in performance.

The Canadian 261 in3 six cylinder 'Strato-six' produced 148 BHP @ 4800 r.p.m.; 8.5:1 Compression Ratio in 1958, and then 150 bhp in 1959-62.