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I recently purchased a newly restored 1950 GMC 1/2 ton pickup with a chevrolet 235 engine online from a shop in Ontario, Canada. The gentleman I purchased from could not have been nicer or more helpful in getting the truck through customs and delivered . My new truck was made in Canada and after spending 70 years there was restored there by Canadians. Everything I saw told me they had done a quality job and I was quite excited when it arrived in late May. BTW, I live in Houston TX.

On my first drive, I noticed that the engine was running hot but didn't think too much about it. When i looked under the truck later that evening I saw a puddle of coolant and started to get concerned. Over the next several days, I drove it a few times noting that it was overheating in less and less time. I checked coolant level and determined only that it may be too full and let some out- no change. I then drained the radiator and refilled with the exact right mixture of coolant and water and saw no improvement. My fan was turning and my fan belt was tight and I was sure the guys who restored her had replaced the water pump and thermostat so felt like they were not the cause. I could not see any leaks from the engine or hoses and all hoses and gaskets were brand new.

I wanted to eventually add Vintage Air to the truck and so decided to replace the radiator. This did help in that it took 30 minutes to overheat instead of 10 but my problem remained. We checked the radiator/ coolant for oil and gas to insure I didnt have cracks in the head or block and those tested fine. While I started to price small block Chevy engines, my mechanic started removing the head and had it Magnafluxed to check for cracks. He inspected the head gasket(new) and found it was fine but went ahead and ordered a new one anyway just to be sure. We found no cracks in my 848 head thankfully. Then my mechanic put the new head gasket beside the one previously installed and we could see what our problem was.

The head gasket for a 261 had been installed purposefully to restrict coolant flow through the block. In cold climates you need it to run warmer as the cold air will keep it cool whereas in Houston- quite a hot climate- you need the maximum coolant running through. The 235 gasket was placed and she has run cool ever since.

Here is what I and the gentleman who sold me the truck learned: If you are buying or selling a truck or car and will be moving it to a much different climate, go ahead and change the head gasket to allow your engine to run as cool or warm as is appropriate. I was right that the men who restored and sold me the truck did a great job but I -and they- overlooked what now seems obvious - the climate difference needs to be factored in so you can enjoy your baby.

Hopefully this will help prevent someone else from making such a rookie mistake

File this under whodathunk?

Very interesting. I bet they weren’t expecting that old girl to travel so far south!! It is usually the fair weather, sunshine state trucks that find their way up here and not the other way around! (But I’m seeing A LOT of diesel pickup trucks heading south. My diesel was southbound I hadn’t bought it.)

Oh, come now. It doesn’t get cold up here ever, eh?! They likely were doing what ole grandpa used to do! Glad you didn’t have a meltdown. Disaster averted.

I have a huge chunk of cardboard on the front of my radiators for most of the year. We got 4” of snow today. Ugh. How’s the sun?

I'm pretty sure everything will be fine. I will say this once again. The original dash gauge can be normally way off. I put Mr. Gasket Thermo caps on Everything. It may not hurt to put an overflow tank on. One of my AD's came stock with that optional item. One question, did the Canadian fellows use Roberts screws? During that time period all Canadian Chevys and GMC's had them rather than Phillips or GM clutch head screws. Roberts screws had a tapered square head with a special screwdriver. There are articles on line about the Robertson screw and driver. Doc.

So, the engine will have a different head gasket based on where it will be sold?

Seems like it had the wrong head gasket all along, it gets hot in the north in the summer, easily hot enough to require a top notch cooling system.

That's a load of bunk. Whoever put the WRONG gasket in your 235 just screwed up.
The thermostat is what regulates temperature, not putting an incorrect head gasket in place that blocks some of the coolant passages.
True story.

Exactly what I was thinking.

I agree with klhanson and Green_98. The builders inadvertently installed the wrong gasket, not knowing the extra cooling between the cylinders needed for the 261. It would have overheated in the north pole given enough time.

A newly restored vintage half-ton would probably never see winter.

That is really interesting. I am going to have to look at my pile of 261 gaskets to see if they have the same restrictions.

Years ago when I bought my 261 engine from a Junk Yard, I was told it was a 235 and out of a 59 school bus. When I got it home and ran the numbers it turned out to be a 59 261, (lucky Me). It had been rebuilt before (was 0.30) over size but had rusty cylinders from sitting in then yard. But it had a 235 gasket and a 235 head (848 head no steam holes). When I had it bored 0.60 over and reassembled it I drilled the steam holes in the head, and used the correct gasket. I always wondered if it would make a difference not having the right gasket and the head not being the correct head, (steam holes).

When I first looked at pictures and read the thread, I thought Docisin was talking about just the “steam” holes between the cylinders. After really comparing the gaskets, I didn’t realize that there were so many differences between the two. You can really see why the Docisin 235 would overheat using the 261 gasket, but don’t ’see why the first three cylinders on a 261 wouldn’t overheat.

Interesting, I learn something everyday!

There was a TSB issued in late '57 that mentions a production change to the model-year 1958 261 block and head gasket, specifically to reduce coolant flow at the front of the head and improve it at the rear. The change was stated to improve temperature distribution through the block and head, resulting in improved component life. (The change has nothing to do with locale or seasonal changes.)

The TSB details updates for earlier model-year 261 engines. One of the rear-most cooling passage openings in the block gets drilled out to 3/4", and the alternative gasket that restricts flow to the front of the head is specified.

The two images show the TSB as issued December 9, 1957.

It was by chance that I recently saw this TSB. I picked up a set of original copies of the late '57-'62 TSBs and '59-'61 Service News. Paging through gives a pretty interesting view of what was going on in the service departments in that era. Starting in '58, a dominant theme in the TSBs was servicing the Turboglide transmission, and then in late '59 through '61, a ton of material for Corvair service and customer complaint resolutions.

Doug

What Doug posted makes sense. The gasket on the right in Phil's picture has smaller holes on one end. Both gaskets appear to be symmetrical between cylinders 3 and 4 (could be installed with either end to the front). It's possible that the used gasket was installed with the smaller holes to the back instead of the front, which would restrict flow to the rear cylinders and increase it to the front, increasing the normal short-circuit flow thru the front of the engine (path of least resistance.) I have seen head gaskets that have "this side up" stamped on them, probably for just that reason - keep someone from installing them with restricted flow holes to the back.