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Old 02-03-09, 21:28
Bob Carriere Bob Carriere is offline
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Join Date: Mar 2003
Location: Hammond, Ontario
Posts: 5,191
Default Personal experience and readings....

Bonjour Guy

I have rebuilt a 261 for my C15a cab 11.

First of all cams ( and many other parts) are exchangeable between 235 and 261.

Keep similar assemblies together to respect the engineering designs.

235 car engines and 261 car engines (usually in Pontiacs in Canada) had hydraulic lifters..... I believe you may find some early 235 (truck?) engines with solid lifters. The whole valve train assembly can be interchange but as a total unit. We were replacing a bent valve push rod on a 261 for Grant and our parts box contained two different manufacturing styles and 3 different length.

Canadian Pontiac from approx. 1957 or 58 up to early 60s can be 261....
Chev truck..... big trucks..... some large 3/4 ton pickups.... circa 1955 to 1961 would have 261 engines....... easily identified by the Captains bars above the starter motor.... more details are available from Chev Stovebolts site... engine ID.

Heads are interchangeable between engines and the best combination is a 235 head ser #####848 on a 261 block.... steam holes will have to be drilled in the 235 head..... a 261 head gasket will guide you for location.

For a CMP where bottom end torque at low RPM is more desireable than absolute top speed a 261 truck engine is far superior. A 261, from a 3 or 5 ton truck, will have solid lifters, block will be drilled for a full flow external oil filter which you can relocate anywhere along the frame, ####848 head and original carburation should give you about 145 BHP.

Forget getting the head shaved to increase compression..... just enough to set it flat is all you need. On a Chev engine, if you wish to significantly raise the compression you need to shave the deck of the block... or top of the block..... an expensive process since the crank, rods,piston and rings need to be installed to check the head space between Top Dead Centre of the piston and the space between the head/valves..... in some extreme cases butterfly cuts need to be machined in the piston top. All in all a very expensive process unless you wish to drag race your CMP

Remember a stock 261 will give you approx. 145 bhp compared to the original 216 at 82 horses..... assuming all the horse are pulling on that day!!!

Phil Waterman runs a C30 fully loaded with a large radio box and loaded with water tanks for his shower etc..... and I have followed him going up long hills in Connecticut at 50 mph steady..... in top gear.

Any of the civilian 235/261 will give you nightmare when installing the waterpump.... you will need a good rebuilt 216 pump and a "hay-dapter" plate....... and the carburator linkage for the right hand drive CMP will need some creative fiddling to make it work and look semi original..... or you can cheat and use a throttle cable. When you get to that stage Phil and I will gladly walk you through the fiddling part.

The hardest part to find in rebuilding the 235/261 is finding good rebuilt rocker arm assembly....... they seem to be in high demand.... everything else is easy enough to find.

Try to get a complete set up engine transmission unit.... or at least engine bellhousing and flywheel clutch assembly.

The 261 will bolt up to a 216 bellhousing perfectly..... but you should try to keep the 261 large truck flywheel...either the 10.5 or 11 inch... with matching clutch and matching 12 volt starter.... ring gear must match starter gear. The heavier flywheel will store more torque.... clutch for 261 are easier to find and can be ordered with heavy duty springs and plate compound.
It will allow more clutch riding if you are so inclined!!!!

Don't forget you can intall a late model 216 valve cover on your 261 to further hide its non original feature.

The 261 should get you a "bit" more top end speed with out over revving your engine....... but remember CMPs were not design for speed.... front axles can shake, brakes are 1939 design, visibility side and rear is not ideal with right hand drive........ respect the machine and it will outlast you...
after all we are playing with trucks that in most cases are older than we are.... even mine.....!

Phil..... did I forget anything or overstate myself...? We both have pictures to help you out....

Just a closing note..... finding a good reputable engine rebuilder can be a challenge...... talk to local hot rod team members or farm tractor shops for recommendations. Rebuilding a 261 was $3100. back in 2003 including all parts, balancing reciprocating parts, and assembly..... basiclly kept the block head and crank and replace everything else...... crank at 10 under cylinders at 20 over. Engine came out of a 5 ton 1959 fuel delivery truck with 85K. miles.

Good luck.... keep us posted (with pictures) if you go that route.....

...and if so inclined you can even visit the Hammond barn.....

Booob
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Bob Carriere....B.T.B
C15a Cab 11
Hammond, Ontario
Canada
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