Inliners International Forums General Discussion Engines 235 head on a 261

Is there any advantage of putting a 235 head on a 261? Also the difference of a holley 390cfm 4 barrel and a weber 2 barrel? Thanks

Many of the 261's have the same head casting # head as the 235's, they are just drilled for the steam holes.

In Frank McGurk's day a 235 head was a good way of upping the ratio --dunno if that was based on advertised ratios or if the were actually cc'd--he said it was better than milling because of having to sink the intake valve and shortening the intake stems when milling the 216/261 heads (261s were like 7:1 and pass. heads were like 7.5 up to maybe 8.25 around '57)--what made the diff?--now we're talking here of pre 1955 stuff when cc-ing wasnt a national pastime.
I had a '54 pass. 235 head on a '59 .060 over 261, and a '56 pickup 235 head on '62 .060 over 261. Both didnt like cheap gas- the latter had a TRW 270/280ish cam, and the former a stock 261 cam. The stock cammer was in a 6 volt '54 chevy and was a hard start in the summertime, the trw cam motor was in a 12 volt '56 pickup always easy to crank. Sorry to add to the confusion.

After talking to James Larrowe about a 261 he has, he told me that the 235 head will raise the compression 1/2 a point to around 7.75:1. This was a common swap on trucks used at higher altitudes.

There is a lot of information about the 235"/261" head swaps, and an explanation on the steam passages required for the siamesed 261" blocks in past posts. Do a search for 261 steam holes.

Tim

Here is one the many treads that Titen mentioned, this one showing the combustion chamber volumes for four of the common 235-261 cylinder heads.

The 848 head came on most, if not all, 1956-62 235s, and was sold as the replacement head for 1953-55 235s. The 913 was the production head for the 1954-55 235. The 850 was the production head for the later (1957?-62) 261s. I'm not sure what the 570 was. The production head for the early, low compression 261s?

The cylinder head volumes shown do indicate almost exactly a 0.5 increase in compression ratio on a 261 by replacing an 850 with 848. The example Iworked was for a 261 starting with a CR of 8.0, the advertises spec value for a 1958 261.