Inquiring minds want to know? Is it the fact that they have more cubic inch displacement, which is not neccessarily as good. Are they better designed? I've loved every babbit pounder i've ever had! What makes a full pressure 235 or 261 any better? Talk to me! Need to know! Is it that you like green motors? Let's start a dialog for the 350 crate motor boys!
The 261 C.I. Stove Bolt Engine O.K. , there's a number of little things that all come to-gether to make it the engine of choice for to-day's driving needs : Revised camshaft profile that gives better breathing & thereby increased power & economy as well as more power at higher RPM's than the 235 cam does . Steam holes drilled between the water jacket in both the head and the cylinder block for less flashover (overheating) when driving in dense traffic . Redesigned connecting rods that won't snap off at the wrist pin from high RPM like 216 & 235 rods do (really important !). Larger bore for increased volumetric efficiency at all speeds & loads . Lower compression ratio via revised combustion chambers to reduce ping & knock under heavy loads with low quality or unleaded fuels . 1956 & later 261 engines have full flow oil filter plumbing built into the block for longer life . There's more but those are the salient points . This engine was introduced in the schoolbus chassis and offered as an extra cost option and was used in many in town delivery vehicles , there's many still to be found in junked Dubble-Dutti vans (' P - Vans ')
Let me rephrase my question First let me say "thank you" for the write up on this. Second, i probably over simplified on the other post when i asked if all a 261 was was a bored out 235. Let me re-ask the question. I assume that you can bore out a 235 so that it displaces 261 cu in. Is that where the similarities end between the 235 block and the 261 block? Or maybe another way to ask it would be this: Assume a fella has a 235 engine, complete, but in need of a lot of work. Would it be possible to make it a 261 or is that Mission Impossible?
Anytime you rebuild a 235 you should swap in a 261 cam & lifters . Fitting 261 rods is good too , -if- you find a set . There's a Web Page on converting a 235 to full flow oil filter , also a very wise thing to do . I once saw a page on drilling the steam holes , that's prolly the very best upgrade you can do to a 235 or 216 .
