Cooling problems on my GMC 250- have a ?

[68gmsee]

My 68 GMC is a 250, three on the column with p.s. and p.b. with the stock, solid blades fan.

The temps are in the high 90's here in Texas and it's been running a little hotter than I like. I think it started some years ago after I had a local shop bore it .030 over.

Here's what I've done so far: Replaced the water pump, all hoses, added an overflow bottle and bought a larger three core radiator from a local radiator shop.

I'm considering a 4 core radiator or maybe an aluminum one if it would help. But, I would like to stay away from electric fans at this time.

My question is: Would adding a radiator shroud help cool it down some?

[zeeklu]

I had a problem with my 292 and did the same things . It ended up being a bad gauge. Chris

[LockDoc]

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My experience says a shroud would help....

LockDoc

[68gmsee]

I checked and the guage is okay. If I remember correctly the temp, when it gets overheated, is in the 200+ range. It actually does the "hot sigh" when you turn it off. But, only when the outside temp hits the 96 to 98 degree mark like these last few days.

LockDoc, the only thing is will a v8 shroud work on a six?

Seems to me like it should but don't know. Has anyone out there put a shroud on a six?

[N2GMTrux]

I have a 71 C-10 with a 250 in-line six. I have a four core radiator with a small block chevy radiator shroud LMC part# 32-2820 shroud W/O A/C. I also run a 18 inch six blade fan with fan clutch. I used to have overheating problems,,,,,,,, no more problems runs 190 degrees now....

All my parts are used though shroud from a 1972 C-10 with a 350 engine,,,, the fan blade and clutch is from a 76 Chevy C-10 with a 350 engine.

Santiago

[68gmsee]

Originally Posted by N2GMTrux

I have a 71 C-10 with a 250 in-line six. I have a four core radiator with a small block chevy radiator shroud LMC part# 32-2820 shroud W/O A/C. I also run a 18 inch six blade fan with fan clutch. I used to have overheating problems,,,,,,,, no more problems runs 190 degrees now....

All my parts are used though shroud from a 1972 C-10 with a 350 engine,,,, the fan blade and clutch is from a 76 Chevy C-10 with a 350 engine.

Santiago

Thanks N2GMTrux. Going to start on it tomorrow. I know that the temp is not that hot from what I read in other posts, but man, I just don't like it when it gets above my comfort mark for the engine.

I do have one question regarding the 18 inch fan. Where did you get it?

I have a fan with clutch that I bought off ebay for my 69 with a 350 but the mounting holes don't match up with the ones on my six. Hmmmm, come to think of it, I really haven't checked to see if they match my 350 engine...

['68OrangeSunshine]

I have a 292, bored .030 over, in a '68 Chevy C/10 Stepside.
After a rebuild -- as it got into the Tucson summer -- the engine started getting hot enough to sweat off the timing tape on the HB.
I use a 3 - core V8 radiator (wider), just the stock finger guard, and a flex fan. I found the higher temps [+220*] were due to a 70% coolant/water ratio. I thinned it back to 50/50 and the temps went down. I run a 195* thermostat year round.

[N2GMTrux]

The original water pump I had on my six had only one set of mounting hole on it,,,,,, I think it was original "at least it looked like it was"!!! The new pump I bought at Auto Zone had two sets of mounting holes. I used the wider mounting to mount the 18 inch fan with fan clutch. My original four blade fan mounts on the narrower hole setup,,,, if this makes sense. When you go to the wrecking yard look for a 73 to 78 chevy truck or suburban. Take a tape measure with you and measure the diameter of the blades. It needs to be 18 inches or smaller to work inside the radiator shroud. Also look for a fan clutch with a center spring meaning " Thermo clutch". Also get the water pump pulley.. I bought two different pulleys from 350 chevy engines, one was about six inches around with two v-belt pulleys and the other was eight inches across with two v-belt pulleys. Both worked but was easier to find the proper belts for the larger pulley.

The main question you need two have the original engine stands and motoer mount on your six banger,,,,,,,,,,, if for any reason you are using 73 to 84 engine motor mounts and engine stands,,,,,,,,,,,, the stuff mention above will not work "I've done it" does not work!!! The original engine mount set up puts the fan centered in the fan shroud. The 73 to 84 mounts sits too low and chewed up my first fan shroud.

Hope this helps..............

[68gmsee]

Thanx for all the help... Truck is all original except for ps and pb and the .030 over on the pistons. Here's the action plan:

1.Today I'm going to do the easy things first. Reverse flush the engine and radiator and replace the anitfreeze. I'll make sure it's 50/50 as '68Orange mentioned.

2. Then I'm going to double check the t-stat. I bought it new couple of years ago since it had the original in it. You never know on this new stuff you buy these days.

3. If it still runs hotter than I like, I'll order the shroud and start junkyarding tomorrow to look for a fan, pump pulley, etc.

After that I'll get serious and maybe consider a 4 core radiator or resort to electric fans. I'll figure this sucker out yet and let you know what happens. Maybe it's something as simple as the 50/50 mixture or thermostat..

[pritch]

I put a V-8 radiator and shroud on my panel-I need to move the fan back a little to the proper location in the shroud, but I never get hot enough to worry about it. One other thing, at least on mine, I had to move my bottom rad mounts to the outer holes-the rad is a little wider. I remember that being a PITA, moving those. The top ones are easy.

[68gmsee]

Today, the first thing I did was flush it. Then I went to the auto parts store and got some antifreeze. While I was there I got a new cap. The guy at the counter said the recommended pressure was 13 lbs and the one on the truck is 16 lbs.

Not sure why I have a 16 lb one. I replaced it years ago when I bought the 3 core radiator and maybe the rad shop gave me the wrong one.

Anyway, I then took the 180 degree t-stat and put it in a small pot. I used a candy thermometer and made sure it opened at the correct temp and stayed fully open until it cooled back down.

Then I filled the rad up with about a 60 water/40 antifreeze mixture. I drove it around the block for a while and it stayed steady just slightly above the first mark (that's my comfort mark). I'll take it out on the main roads and give it a more thorough test tomorrow.