The Stovebolt Site Forums The Shop Area Engine Shop 235/261 differences???

I have a 1957 chev with a 235. Just picked up what I believe is a 62 261 from a Canadian Pontiac. Whie checking numbers, I found that both engines have the same head casting number. Is this usual or do I have two of the same engine? Stamped serial numbers on the block are different but do not seem to follow any pattern that would tell when they were cast. This may be a Canadian Engine thing. The only real difference is the placement of the oil filler in the valve cover. The truck 235 has it up front while the later 261 has it in the center. There are no other numbers to be found. Any help in discerning what I have would be appreciated before I spent a good chunk of money?

cheers,

Ryan

I believe the 235 and 261 can use the same head.

Both my trucks have the same head. I do believe my 261 fills in the middle. But that can be changed, since the heads are the same.

I believe on this website, in the tech section is what you are looking for. I believe the 261 has what they call captain's bars in their number.

235 heads do not have the small steam holes that a 261 head has.Easy to do with a drill however.Later 261 head casting numbers end in 850.There are web sites to check the casting numbers on the right side of the block,try www.inliners.org .A 261 has beefier rods with larger piston pins and a bigger bore than a 235.The rest is pretty much the same.Some early 235 engines had the bars down by the starter.

Tony,

Any advantage on the 235 head over the 261? Does the 235 flows better? I've heard the steam holes stuff before and it is like that, You have to drill them to use the 235 head on a 261 engine, but does this swap has any benefits? Ain't the 235 chamber smaller?

I have a 261 block in my 57 Chevy truck. It was bored .060 over. I used the 848 head from my original 235 & milled it down a bit. I did have to drill the extra holes for the coolant to match the block. However, outside of the trepidation of potentially destroying a difficult to find head, it was really no big deal. So far I have excellent compression on all cylinders. It is a big difference from the 235. This is a fairly straightforward low-cost (for this type of engine) proposition that yields excellent results.

Thanks guys! I found some of the tech info on variuos web pages and went home last night to check things out. You might like this story! I had the numbers to check and their location on the engine but when I looked in the spot the block casting was supposed to be, there was nothing there. Just flat smooth clean paint (I had washed the engine over the weekend). It was smoother than the surrounding painted metal in fact. After taking a wire brush to it, off came the paint, then a thick layer of oil and grime that was concealing the number! A previous owner hadn't properly cleaned the beast before painting it!

It is indeed a 261 and the one in the truck is a 235. Now I can put my fears to rest and start stokin the new stove1

cheers, and thanks,

Ryan

Alex, the 261 head has a slightly larger combustion chamber to lower the compression ratio for truck use.Other than that the ports appear to be the same as a 235 head.Yes the 848 head has the smallest chamber of the 235 heads with the 261 head having the largest chamber of the 235/261 engines.