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Jul 21st, 2025 | | | | Joined: May 2005 Posts: 235 Shop Shark | | Shop Shark Joined: May 2005 Posts: 235 | So I haven't posted in awhile mostly to being pretty busy.... My 261 has a crack in it that is so bad that you can watch the water pour out of it, so I bought an engine from a guy I know. Its a 235, but one like I've never seen before, and I have seen a few. It has an oil distributor, and no holes in the head for a valve cover.... I know.. sounds like a 216 right? but the pushrod cover goes to the top of the block not all the way up the head... See? Weird....  | | | | | Joined: May 2006 Posts: 8,351 'Bolter | | 'Bolter Joined: May 2006 Posts: 8,351 | '50-'53 low pressure 235. Can you post the numbers, either casting or serial?
Bill Burmeister
| | | | | Joined: May 2005 Posts: 235 Shop Shark | | Shop Shark Joined: May 2005 Posts: 235 | 3701946. Cast number right Of fuel pump
3701887 head casting number.
It doesn't look like a low pressure motor. Though I didn't pull the pan.
Last edited by lostmy47; 06/15/2015 11:45 PM.
| | | | | Joined: Sep 2001 Posts: 29,262 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,262 | 3701946 - 1953 235 truck block
3701887 - 1953 235 truck head
The oil distributor on the manifold side is a feature of a low-pressure engine.
The 1941-1953 truck 235s were low pressure.
As posted by Bill, the low side cover on a low-pressure block is indicative of a 50-53 235. | | | | | Joined: May 2005 Posts: 235 Shop Shark | | Shop Shark Joined: May 2005 Posts: 235 | News to me. I'd never seen one. Hopefully it lasts until I can find a new 261 block.
Is there any reason you can't make a 235 into a 261? Aren't the blocks mostly the same except for bore size? | | | | | Joined: Sep 2001 Posts: 29,262 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,262 | Someone might say you could morph a 235 into a 261, but it would not be a simple matter of increasing the cylinder bore. You would also have to add coolant passages (the 261 has 2 additional coolant passages between each pair of cylinders). Some people use the silly term "steam holes" for those additional coolant passages (GM called them coolant passages).
The 261 also had a cam with slightly modified lift (same lift as the cams in 235 Corvette engines). That style cam can be also used in any other high pressure 235s (and, I think it was used in later 235s). | | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | The build I am doing now comes as close as you can get. A 235 engine with a .080 overbore (making it a 246) with full flow oil filtering, PCV and an 848 high compression head. But not with a pre-1954 235 engine. You need full pressure oiling to do some of these modifications. The 261 document is here: http://devestechnet.com/Home/TheVenerable261The 235 rebuild is here: http://devestechnet.com/Home/Project1959235 | | | | | Joined: Sep 2001 Posts: 29,262 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,262 | Did you use a 261 cam in that 235, Deve?
(sorry, I am lazy/busy and did not look at the 235 rebuild link) | | | | | Joined: Feb 2004 Posts: 28,674 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 28,674 | It's impossible to get a 3 3/4" bore into a 235 block without hitting water, or at least getting so close the cylinder walls will fracture the first time the engine is run. The block core is different on the 261, with the cylinders "siamesed" together like the small block 400 V8. That's why the extra cooling passages are in the top of the block and the cylinder head, to eliminate hot spots when the coolant can't flow between cylinders.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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| | | | | Joined: May 2005 Posts: 235 Shop Shark | | Shop Shark Joined: May 2005 Posts: 235 | Thanks Jerry. I knew there was a reason I couldn't recall... I thought about boring it sleeving it and boring it to size...
think I'll look for a new block.
| | | | | Joined: Dec 2000 Posts: 3,399 Gas Pumper | | Gas Pumper Joined: Dec 2000 Posts: 3,399 | No. I used a 235 cam and sent it out for a regrind. I do not know enough about doing a 261 Hydraulic cam in a 235 car engine or what the real benefits would be. Have we talked about this before? | | | | | Joined: Sep 2014 Posts: 385 Shop Shark | | Shop Shark Joined: Sep 2014 Posts: 385 | Cracks suck. I just got a 57 261 from a guy for a side rebuild and after steam cleaning it i found a crack full length from front to back just on the intake side. Was lucky enough to get another block from a different guy later that same day with the same casting number and in mint shape for $40. | | |
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