The Stovebolt Site Forums The Shop Area Engine Shop 235/261 Performance

Has anyone hopped up a 235 or 261? Anyone ever supercharge or add a turbo to one?

My 54 short bus is about 150hp. I would keep the drive train original if I could get some more torque out of the beast. I want to be able to climb the hills in Tennessee and North Carolina without doing it in granny gear.

As for the 261, I am thinking of rebuilding it, boring it 30 over, hydraulic cam, mild head porting/cleanup (plus 3 angle valve job and replace exhaust seats with hardened), headers, intake and a bigger carburetor (2bl or small 4bbl.) Problem is the stock 7.8:1 stock compression. I would like 9:1 to 9.5:1 (max).

Does anyone make a higher compression piston, possibly a forged or hyperutectic piston? Is there any way to get more compression without milling the head and boring it way out?

From what I have read, the 261 lower end is burly, with a forged steel crank and rods. It seems like it would be a good candidate for a supercharger or turbo application.

There is a guy on youtube.com that put a turbo on one. See first listing under http://www.youtube.com/results?search_query=261+turbo

The motor in the video seems pretty worn out, sure the makeshift turbo set-up is primitive, but this does raise interesting possibilities, and is pretty easy to plumb. Any ideas?

you can get high compression pistons........not sure of the numbers/compression ratio,, but a 261 i picked up last year,,when i tore it down for rebuild found it was bored .125 over and had jahns high compression pistons....just fired it up couple weeks ago,sounds awesome.... haven't drove it,,still a few loose ends..

What year 261 do you have? If it's a pre-57 block, it most likely will not be drilled for hydraulic lifters, so you will have to stay with solids.

The 261 engine was lower compression than the 235. The 261 cam had a modified/moderate lift that was designed for better higher-speed torque than the 235. I drove my Suburban in VA in the early 70's - in high gear from the valley to the Skyline Drive. It was far superior to my old, original 235.

Ross makes about anything you could want in a custom piston. If the current ones are good and you don't want to replace or bore the block I'd certainly mill the head. If it's good it will handle a lot of milling but it would be wise to double check the valve clearances before having it done. I can't advise you on how much to remove to give you a point of compression increase but perhaps others can. I would consult Ross on this as it is their business and they have a lot of experience.

If you drill out the extra water jacket holes in an "848" 235 head and put it on the 261 you get quite a bit more compression. That's the easiest way to improve a 261 for minimal cost. The pistons are expensive.

Hey, thanks a lot everyone for the good advice. The motor in my bus should be a 1954 261. I may consider a later 261 block when rebuilding so that I can run a hydraulic cam, as they are quieter and require little maintenance. Plus, I hear that the later blocks had a full flow filter, versus the bypass design.

I'll check with Jahns and Ross for pistons. Don't know if I need forged, but the hyperutectic would be ok, too.

Cast .060 pistons over with a milled head might get the compression ratio high enough for my needs.

Thanks again for the help, and take care!