The Stovebolt Site Forums The Shop Area Engine Shop 1941 GMC

I rebuilt my '41 228 several years ago and I haven't ran it very much at all. It just never seemed to run as good as it did before...I started it last night and it seemed to want flood and smoke a lot. I don't think it's the carb, but I do think it is in that valve/flap (heat riser?)thing below the carburetor. The paint is burnt badly below the carb and when I shut off the engine and got out to look, the thing was smoking! I am guessing that maybe the valve is stuck in the wrong position or isn't moving towards open as the engine warms up. Anybody have this problem? I see it a lot on Chevy sixes (paint burning). Also, for anyone who isn't familiar with the GMC 228, It is basically where the idea for the Chevy 235 of 1954 came from. It is not a babbit pounder and it has full pressure oiling. It just doesn't have a whole lot of power.I sure would like to know why the paint burns off so bad...Thanks in advance. Jim

At one point after I had rebuilt my 235 in my 62 Bel Air, it was running really hot. So much so that the fuel was vaporizing in the carb. We thought it was a stuck thermostat, but it turned out that the oil filter was filling up (bypass type filter) and the engine wasn't getting enough oil.

One should be able to move the weight, by hand, when cold. If not, then it might be stuck in the hot position like you said. Work it over w/ penetrating oil gently trying to rotate it, hot and cold. Careful, easy to twist off.

I finally got back to look at my truck last night. Wow. There is NO counterwieght on the heat riser! It was rusted in the closed position. I guess the little coil spring closed it when it got cold, and since I haven't run it in a couple of years, it just rusted shut and stayed in that position. I freed it up with a little PB blaster and clamped a vice-grip on the shaft and it is totally free now and runs much better. I don't know how I missed that when I rebuilt it, but I did. I have another intake/exhaust manifold from a '49 that has the complete and working heat riser. I remember not waniting to use the '49 on the '41 because they are shaped a little bit different. I like originality. I know they would bolt up though. I am guessing that the '49's shape might have been a little improved from an airflow standpoint. I got it on my mind to sandblast the '49, paint it to match the '41 and put it on...or, I could maybe attach the counterwieght from the '49 onto the '41. The '41's shaft only sticks out about 1/4" and it is kind chewed up from the vice-grip teeth ( I am apparently not the first person this has happened to.) What would you guys do? Jim

Why not take the manifold off, and have a look see if you can move the guts of the 49 to the 41. If not, I'd just run the 49 until you find a "new" 41.

I've driven cars and trucks with a stuck heat riser. If you move the valve to "not-heat", then the old bus will run okay, but it will take forever to warm up, and on really cold days, it wont run as well. There is a reason Mr. GM put those darn things on there.

The heat riser valve on my 235 was stuck on "heat-on" and after 5 or so minutes of running, the old beast really suffered. I moved the valve to heat off, and then eventually got it free, and the difference is quite dramatic. I also enjoy hearing the valve clang shut after I shut the truck down, and it cools a bit.

Well, my ole truck still runs like crap...Last night I put in a new condenser, cleaned the points, put in new plugs, and completely cleaned and reassembled the carb...and it doesn't run a single bit better. I noticed when I removed the carb that the floor of the intake manifold was wet with gasoline. I also noticed that when I restarted it with the breather off, it had a tendancy to back-fire. Also, when I removed the plugs, they were sooty and black. Could my timing be off? It runs like it has a vacuum leak...poor idle, and no pickup when accelerating. HELP. I've had this truck 45 years and this is the first time it has ever run bad. Jim

I fixed my truck during my lunch break today! I am humbled to say the least. The firing order was wrong. Somehow, some way, I had 1-5-2-6-3-4 instead of 1-5-3-6-2-4! It now runs very smooth again. A heartfelt thanks to all who responded. Jim

We've all had a similar experience, if we have the intestinal fortitude to admit it!