1955 GMC with V8 getting too hot

[Stroked87K10]

Sorry if this gets asked a lot. We just bought a 1955 GMC 100 big window step side for my old man. The truck has been restored and has a 350 with TH350 trans. The truck runs and looks wonderful. But driving around town the engine seems to get hot. It runs all the way up to 200 and a little past. At least that's what the Stewart Warner gauge in the dash says. I believe the radiator is original though I think it's been redone. The motor has only a flex fan in front of it with no shroud. What can I do to keep that temp in check? Thanks in advance.

[OrrieG]

1. Check you gauge, my Chevelle started running hot, turned out the gauge decided to start reading 10-15 degrees hot.
2. Add a shroud. When I converted from my 6 to v8 it started running hot, I added a shroud and all was well.
3. 200 is not that bad. a lot of guys run 195 degree thermostats with 195-200 being the norm. With coolant the boiling point raises to 230+ degrees. I used to roll across the AZ desert at 210 all day long.

[Stroked87K10]

I think it got up to 210 almost 220 and made me nervous. I feel like it smelled hot too. I'll check the gauge. Might use an infrared thermometer to see what temp different parts under the hood reach. I was figuring a shroud would help. Do the LMC shrouds fit with the V8? Any idea which is best? Should I still run the flex fan, or a clutch fan? I figured if all else fails an electric couldn't hurt either.
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[OrrieG]

Read Denee's thread about her fan/radiator problems. It might make you rethink electric fans. If it is a 55 second series (Task Force) you might think about trying to find a big truck radiator. They are 1 inch thicker and longer in the bottom, but mount the same as the stock one. I got one because I am going to be towing and wanted some extra size. Measure your radiator and head to the junk yard. I found a early 70's Ford Torino fit pretty good with some added side supports. I kept the radiator in the stock 6 cylinder position so I have plenty of room. If yours is an early 55 AD truck, the distance between the fan and radiator is usually much less.

[mr48chev]

If it has an electric temp gauge I'd want to know what the true temperature of the engine is in comparison to the actual temperature.

I'd put a real fan on it as depending on which fan it has some flex fans don't pull a lot of air and are intended for race cars that want less drag on the fan. If it's the rv style flex fan it should be able to pull a cat through the radiator but my guess is that you have the one with the thin tapered blades.

Personally I don't think 200 or 210 is hot for a 350 in traffic but if the temp runs at or just above the rating of the thermostat at highway speeds and jumps in traffic you aren't getting enough air through the radiator at that speed or possibly you don't have enough cooling capacity in the radiator. The temp dropping right back down when you pick up speed says air flow.

I had one of those little aluminum flex fans on the 48 as it was all I had room for with the 250 in it and it did exactly what you say your pop's truck does. It would run down the highway at 60+ at 181 to 183 degrees and as soon as I got in traffic in town the temp jumped right up over 200. As soon as I hit about 40 mph the temp dropped right back down. As much as I hate to I may have to go electric when the truck goes back together with the 292 in it but that fan sure isn't going back on it.

This piece of junk here is what I had on mine.

[sqrlnts]

Originally Posted by mr48chev

the rv style flex fan it should be able to pull a cat through the radiator

Good one Mr48.

[mknittle]

I made a shroud for my jeep an it made a big difference.

[xaircav]

The 283 I put in my '53 hasn't budged off 180F since I installed a two row aluminum radiator from Champion. Also, check your timing. Retarded timing will cause an engine to run hot.

[focusedontheprize]

Originally Posted by mr48chev

... As much as I hate to I may have to go electric when the truck goes back together with the 292 in it but that fan sure isn't going back on it.
]

This is what I am running right now in mine. I do not have space to fit a full puller on the front of the radiator so I am running a pusher. It runs a little to warm for my liking, but I have been reading these motors run their best around 195, but again taking it with a grain of salt.

Like everyone else said - run the truck and then take a second reading on the motor temp with an infrared thermometer. See if you are getting the same reading. If you are, try Mr48's recommendation.

For piece of mind could you put an electric pusher fan on to help if the shroud route isn't successful?

[1project2many]

I've got a pusher with a 12" blade. I used a stock fan from a Citation and made a shroud. Fan engages at 212, shuts off at 190, using temp switch from '82 Cavalier. Fan will cycle in traffic or entering / leaving car shows. Radiator from 1956 GMC LCF truck, cap is 14 psi, engine is '63 327 block and 67 283 crank. No a/c, no p/s, no extras.

People want electric fans but really, a proper belt driven mechanical fan moves more air than most electrics when engine rpm increases. I think the next project will include an electric fan clutch if possible rather than an electric fan. That's what the OE's are using in trucks and vans these days. That way I can disconnect the fan when not needed.

[_Ogre]

add a shroud first, then see what needs work
how far away is the fan from the radiator?
you may have a 195* thermostat and that is where the temp should be

[Rude Dude]

Ever 350 I have ran always read around 195 to 200 in normal traffic driven.