The Stovebolt Site Forums The Shop Area Engine Shop Engine issues: 1959 Canadian GMC 9400

Let’s see if this works. The engine has a yellow tag behind the starter, I haven’t got the whole thing washed as well as I’d like yet so I didn’t read what was on it. I live about six hours away. There was still fuel in the fuel pump and gas tank but it smells very much badly, like 25-35 year old gasoline tends to smell. The carburetor was empty and other than a dried out accelerator pump it looks really clean inside. The stuck valve moves a bit but hangs open. I’m not sure how to get that to move. The engine does turn over though the rocker shaft is a bit gummy.

Before you try to start that engine, read a “Tech Tip” about starting an engine
that has sat awhile. Here is a [LINK].

Your gas tank, gas lines, fuel pump, and carburetor will all need to be looked at, cleaned or possibly replaced prior to attempting to start the engine, or catastrophic damage to your engine may occur.

DO NOT attempt to start the engine until you’ve taken the proper steps to insure you won’t damage it. The Stovebolt Tech Tip could save you thousands of $.

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Thank you. I already lubed it up, but one valve sticks pretty far open and the pushrod gets loose. The spark plug is pretty rusty on that cylinder. I suspect it would be best to yank it, pull the head off and look inside.

1959 Canadian GMC trucks came with a 261 engine. Look for captain's bars just behind the starter The M in the square shown in the picture indicates it was manufactured in St. Catharines Ontario. The serial number will probably start with a W.

Head is 3836848, block is 3769716, I didn’t see any captain’s bars. I was hoping it would be a 261 but the block number appears to be match a 235. The carb and fuel pump don’t have tags on them, the carb does have a flat pump plunger and leather cup.

The engine may have been replaced with a 235. The captain bars are hard to see behind the starter and on the other side under the manifolds . The Canadian GMC 261 engines I have seen are green and have a stamped serial number starting with a W ------ on the flat surface behind the distributor.

This engine is painted blue, I am about a six hour drive away from it (I work on it every time I visit), so I can check that number once we get it out of the shed and wash it properly. There is an ‘engine number’ in the VIN plate under the door, T384150. I don’t know if it matches any other numbers but I can hunt around. I was looking at some of the other information on axles and brakes, just what others have posted on here has been helpful to understand possible directions to go with this beast. I think if this engine is in good shape (either with minimal work or a rebuild) I’ll try to use it, if not then I can start looking for a 235 or 261 to replace it.

I took a look inside. There are two stuck exhaust valves, two rusty combustion chambers. The exhaust ports are rusty, intake ports are clean. I’ll pop the valves out, I’m not sure of the next steps, the head is off, engine is still in the frame. The bottom assembly spins pretty well, despite the rusty top of the cylinders.

The machine shop said the one combustion chamber is rusted too much to clean up. One guide cracked when they pulled the valves out though I drilled most of it out and it drove right out after I left maybe 1/16” of wall thickness. I’ve found two heads around here that seem to be ok, I’ll see how it goes when I dig into them. As a bonus they come with the rest of the engines, though I don’t really need all of that. But one thing seems odd, I see heads with 235 casting numbers put on 261 engines with the extra water holes, and I’ve seen this more than once. Did GM Canada use 235 castings and drill their own extra holes for their 261?

Dale,

The short answer is "Yup"!

Check out this recent thread conversation on an "acquired 261".

The answers about the steam holes in the "848" Canadian head (and other Canadian 261 unique info) is well explained in there.

Dan

I would add that a year ago I bought a 261 truck engine from a bone yard in Wisconsin. It was a 62 replacement block (no serial number), drilled for hydraulic lifters, no oil filter, apparently ever though it has provision for the full-flow filter, PCV and the 848 head with valve rotators. The sheet metal was painted yellow and the cast parts painted orange. Yellow engines came in 56 and maybe 57 two tons, I believe.

Most of the reports of 261 heads indicate that they are 848 heads. The US parts books indicate the lower compression 8:1 head whose number I don't have at the moment.

I was looking at replacing the guides and cutting the seats. Has anyone here used the Qualcast guides (301732 and 301527)? I did a search and didn’t see much on here. Thanks again! This is a great community and there’s a ton of information available here.

I cut new seats and installed new valves into a used but decent condition 848 cylinder head, used a Fel-Pro ‘blue’ gasket to put it together, a new Melling pushrod to replace a bent one, and it runs. This is the first crank/start attempt. I only filled the bowl so it quits after the fuel is gone. I’ve subsequently got it idling nicely and you could balance a wine glass on the air filter.
First Start of 1959 GMC

Congrats on getting it running, that's always a major milestone!

Mike B

Thanks! I’ll get more work done on it when spring comes, it’s 400 miles away from my home. I’m planning on rebuilding the brake system and getting the clutch taken care of, that will let it drive safely.

In the meantime I have two and a half engines worth of parts in my garage that I need to deal with, one 261, two 235s. Both of the 235s had the 848 heads, I bought the three engines just to get one decent 848 head, but now I am thinking I should build the 261 and maybe one of the 235s. I have two 848 heads, one is on the engine above, the other I’m just cleaning up and checking now. It actually ran on most of its cylinders but looking at the exhaust seats I am surprised it did that. I also have a 913 head from the 261, it was drilled for the extra coolant holes already.