The Stovebolt Site Forums The Shop Area Engine Shop 1961 remanufactured block

I just purchased a brand new in the crate 1961 remanufactured Canadian block. The part number is 5788673 but I can not find any reference to it. The block comes with new piston, rings, pins and crank bearings.Does anyone have any further information on this?

291????? Maybe you mean "261"? Since it's got 4 main bearings instead of 7, it's obviously not a 292. If the bore size of the cylinders is 3 3/4", it is going to be a 261. Canadian casting numbers are very different than USA numbers, and the 261 engine was used in Canadian "Pontiac" cars for several years. That one had hydraulic valve lifters. The USA truck 261's used solid lifters. If there's a large diameter oil passage connecting all the valve lifter bores from front to back, you've got a hydraulic lifter Pontiac car engine.
Jerry

A 261 was used in Canadian GMC trucks (in at least 1954) - that Canadian 261 would have had mechanical lifters.

I'll see if I can find documentation on later Canadian truck 261s.

that tag sure looks like a part number
what's casted on the side of the block?

part number and casting numbers are not the same thing
multiple part numbers can be machined out of the same casting
-s

Attached below is the part number tag:

5788673 (part number or block casting number - I'll guess that it is the part number).
261 FITTED PASS

Indicating (to me) that it is a Canadian 261 passenger/Pontiac engine, which would use hydraulic lifters.

See if you can find any of the codes shown on this page - USA 261 code locations.

Yes I actually meant a 261 block. Since I purchased the block in Alberta and live in BC I will have to wait until I get delivered to see if there are any other numbers.

I am brand new to this forum and brand new to rebuilding. I have a 1950 3100 with a 1956 235 engine with a 4 speed manual with a stock 10 bolt rear end.My plan is to use my 1956 235 crank, and other items including the head (high compression) 3836848 head and get the steam holes drilled in. I have ordered a water pump adapter , a water pump ,oil pump , fuel pump gasket set, neoprene crank gasket and assuming it has hydraulic lifters (replace my 235 ones with new ones and probably the push rods.

I will get the machine shop to install bolt in crank snout.

I will keep stock carter one barrel carb and try to figure out the T5 transmission in place of my 4 speed , get a 55-60 rear end and I guess sort everything out one step at a time as io figure it to be a three year project..

Once I confirm this is a 261 my question would be what cam to use a 1961 Pontiac 261 cam?

Rick Brown

Is this the same block we had a discussion about a few weeks ago?

https://www.stovebolt.com/ubbthread...1-gm-engine-short-block.html#Post1317986

Mike B

Yep, appears to be the same block. Just saved the engine images from both the previous and this thread. Side by side the wrist pin orientation and a few other details look to be the same. Nice find and I'd love to have it in the shop for a upgrade for my '51 216 truck. As Jerry previously mentioned, a lot of the missing bits can be supplied by a 235 engine.

Good Luck Rick!

RonR

It would be interesting to see if it has hydraulic lifters (Canadian Pontiac 261)?

It would also be interesting to know the engine casting codes.

Generally speaking. "piston-fitted" blocks do not include a cam or lifters, so if the oil gallery for hydraulics is present the engine could be built up either way. Given the rash of problems experienced by a lot of people with recent-manufacture hydraulic lifters, the logical approach would be to use either the Sealed Power or Elgin solid lifter cam with the 261 lobe contour and do a valve adjustment occasionally. As long as the rocker arm tips are in good condition or they have been reconditioned to the proper smooth contour, solids are very quiet. The "Singer sewing machine" valve rattle people talk about from a stovebolt engine is just caused by improper valve adjustment or worn valve train parts.
Jerry

Yes this is in fact the block you had a discussion about a few weeks ago and I bought it for $700. Thanks Jerry on the tip on the cam and using the solid lifters.

Hi all yes this appears to be the fitted 261 block you had a discussion about a few weeks ago and I bought it for $700. My 1950 3100 project had a seized 1956 seized 235 in. Finally got the crank and bell housing off as a unit and then with a piece of wood unseized each piston. But thought starting with a fresh block would be worth it. The cam suggested by Jerry make sense so I will try to track down that cam and go with solid lifters.

I have a feeling I will be on this forum a lot as time goes by as it has been extremely valuable to connect with people with expertise on these awesome old trucks.

earlier this year i found a 261 engine in a Saskatchewan wrecking yard:
head 3836848
block 3769717
still had all the regular bits from generator to carb, it's sitting in a car, not a truck.
maybe i should ask how much $$$ for it
they probably want something crazy like $100 for it tho
-s

Its a nice fitted block you have there! I have two of these Canadian Pontiac pass car blocks. All of the pass blocks I have seen seem to be Drilled for hydraulic lifters. Rods, pistons are 261 specific so you have those. Use a timing gear set for a 261 truck (Aluminum cam gear, which I am pretty sure is all that is offered now as new although you might be able to find a NOS fiber gear, but stay away, the truck gears are better.) Everything else can come from a 235. The Canadian 261 is more like the 55-57/8 American truck blocks in that the Canadian Pontiac pass blocks use the bypass style filter and smaller oil lines (as far as I have seen) even in blocks through the 1962 Canadian Pontiac production as opposed to the 58 and up American truck blocks which were generally full flow filter motors with the larger lines.

Jerry is quite correct as to the hydraulic lifters. The new stuff seems to have a high propensity for failure, mostly collapsing as opposed to taking out a lobe, within a short time of going into service. If you want hydraulics, beat the bushes and get a set of NOS GM or RNOS 56-62 235 hydraulic lifters that are at least 25 years old. Use the 56-62 235 push rods (aftermarket like TRW or Sealed power are better then stock GM as they are a tube type as opposed to the solid GM type which are more prone to bending).

Camshafts, I like Schneider, others like Delta or Elgin. For the head, the Canadian Pontiac 261 motors used the 848 head. The benefit of finding a real Canadian Pontiac 848 head, the steam holes are already drilled and at the correct angle. Otherwise, use a 235 848 head but remember to drill the holes.

Crank can come from a 235 (I have a 56 235 crank in one of my 59 Canadian Pontiac 261 blocks). All the tin can come from a 235. Timing plate - depends. If the timing plate for the installation you are doing calls for the motor mount as part of the plate, just swap over what you have or get what you need. Rockers, getting the right finish and curvature on the rocker arm tips, and a good fit between the rocker arm and the shaft is not something everyone can do, me included. Rocker arms unlimited in California can rebuild a set for you but be forewarned, not cheap. New TRW and Sealed power sets turn up once in a while on ebay, usually less then a rebuild but its hit or miss finding a set.

That flitted block you have is going to be the basis for a really nice motor for you. Dive in and enjoy the build!

Mike I do have the complete head as well as hydraulic lifters, rocker arms and push rods off my 1956 235 should I not use any of these parts?

The head yes as long as you drill the steam holes in the head. Those 261 motors are like a 400 Chevy. The cylinders are siameased and each pair of cylinders has a pair of steam holes in the block. A real 261 head, which you can also use, has those steam holes already drilled. To use an 848 head on the 261 block you need either the Canadian Pontiac 848 head with the holes already drilled, or you have to drill the 848 head you have. The rub is that they have to be drilled at the correct place (use a 261 head gasket as a template) and at the correct angle (which I forget offhand what that angle is). No to the hydraulic lifters from the 56 unless you are swapping the old cam in (which I myself would not do).

If you are gong to swap the 235 cam in (which I don't actually recommend), make absolute sure you keep the lifters in the proper order as they have to go back onto the cam lobe they came out of. You have a nice new fitted block with nice GM cam bearings installed. Putting a worn 235 cam in runs the risk of low oil pressure from worn cam journals and other issues. You have gone this far, go a little further and use a fresh cam.

So if you are getting a new cam, you will need new lifters, either hydraulic or mechanical (for mechanical use 56-62 truck solid lifters. The 55 lifters are usually the milk bottle style lifters. Nothing inherently wrong with them, but they were designed to be used in a block that is slightly different then the later motors so I use the later style lifters.)

Push rods, you can reuse but again, you want to keep them matched up to the rocker arms they came from primarily because the adjuster balls are now well worn into the push rod cups. That being said, the stock GM push rods are solid rods. They bend easier then the aftermarket push rods and the after market push rods are tube type (and not that expensive to replace.) Rockers, I like rockers in good shape. Shafts that are not galled, new adjuster balls, rocker tips smooth and correctly contoured. I just don't like using old unrebuilt or unreconditioned parts on a new build. It just seems to me to invite unnecessary headaches down the road.

Comp Cams will build a set of NASCAR-strength pushrods in whatever length you need, and they will install upper and lower hardware to be an exact match to the lifters and rockers. When I'm modifying a pre-848 235 head for more compression, I get with the custom department at Comp to fabricate pushrods with the right length and hardware.
Jerry

Thanks Mike and Jerry for the detailed response. It makes sense to do it right the first time even though it is more expensive short term. Can not wait to get started.
Rick

If you haven't checked it out already, you might want to read our Tech Tip on rebuilding the 261

I finally have the new 261 fitted block in my possession and out of the crate, The casting number on it is 3769717.
I am ordering a new spin on oil adapter from Devestech and as far as I know the machine shop does not need to make any other aelse for the spin on oil adapter other than installing the dowel plug .63 below boss for full full oil. The machine shop will drill the steam holes in my 235 (3836848) head, The machine shop will insert the dowel plug(came with fitted block along with hollow head bolt which i will use with the 235 head) . Use the hollow bolt as I am using solid lifters,, The machine shop will install the water pump adapter plate to allow the fan to be at the middle of the rad. .They will inspect and grind my 235 crankshaft and drill the snout for a bolt,

Is there anything else they should machine while at their outside of re working the head new valves etc?

My pushrods are 11 inches and a quarter long so I assume I replace with the same length.?

I finally have the new 261 fitted block in my possession and out of the crate, The casting number on it is 3769717.
I am ordering a new spin on oil adapter from Devestech and as far as I know the machine shop does not need to make any other drilled holes for the spin on oil adapter. They will install the dowel plug .63 below boss for full full oil. The machine shop will drill the steam holes in my 235 (3836848) head, The machine shop will insert the dowel plug that came with fitted block along with hollow head bolt which i will use with the 235 head) . I gather I use the hollow bolt , I am using solid lifters,, The machine shop will install the water pump adapter plate to allow the fan to be at the middle of the rad. .They will inspect and grind my 235 crankshaft and drill the snout for a bolt, I will get them to determine rod bearings for my remanufactured rods,

Is there anything else they should machine while at their shop aside of re working the head new valves etc?

My pushrods are 11 inches and a quarter long so I assume I replace with the same length.?

Rick

To use the 61 block with the 56 head, yes you want to use the drilled bolt, but don’t forget, there is also a plug that has to be used.

Great thread with a lot of good information that I may very well benefit from.

Rick Brown, would you mind changing the thread title to reflect this is about a 261. Would be a helpful for others when using the search function. If unable to edit, perhaps the Mods can make the change.

RonR

I have changed the title to 261

You can only change your posts. The forum Moderator will have to change everyone else’s, one at a time. A bit of a task.

Jerry and Dragsix, You spoke of the high failure rate of newer hydraulic lifters. Where are you getting that information? I have seen nothing on any of the forums that I visit. I’m not a professional engine builder so may not be privity to sites where this information exists.

Personal experience for one. I had one 235 motor about 7 years ago, brand new build for a friend, that I had a devil of a time with the lifters. Three collapsed. Two just after break in and one in less then 200 miles. Had to replace with NOS. And my friend who owns the machine shop that I use had a customer's 54 powerglide motor that had four or five from two different sets collapse until I gave him a set of NOS. Also, Patrick's Antique Trucks, when they were still in business, detailed the problem in their catalog. There have been posts either here or on other sites. So this is not an unknown problem and as far as I know, the off shore junk manufactures have not fixed the problem.

Its one of those things, you might get a good set, you might not.

I understand that ‘off shore’ replacement parts continue to be a constant problem. I, unfortunately, have personal experience with it. I, like many of us here, troll the various web sites trying to find NOS parts.
Thanks for your insight.

do you mean the dowel plug that has to be inserted .63 below the boss

do you mean the dowel plug that has to be inserted .63 below the boss

No, you are confusing the dowel on the lower drivers side of the block that was used for full flow oil filter vs bypass oil filter.

When using a later short block (59 and up with the improved oiling system) and an earlier head and rockers (55-58) you need to restrict the oil going to the rockers, otherwise it will flood the head and rockers with too much oil. So if you read the instruction sheet carefully, you will note that there are two components that came with these late fitted blocks to make this sort of swap, the hollow bolt and the tapered plug. The tapered plug gets installed in the deck of the block to stop the flow of oil through that port, and redirects the oil to the drilled bolt. Its actually very clever. So you have to use both. Now, if you are using a 59 and up head and rockers, you don't need the bolt or the plug as the 59 and up heads and rockers are designed to handle the extra pressure and volume.