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I have a 76 that heats up after all new coolant system.
water pump, 160 thermostat, hoses, and radiator completely overhauled.
It is all original and I even have the shroud.
Any ideas would be great.

Thanks,
Scotty

are you losing fluid, are you using the right weight of oil, is your oil full?

Stupid question, where is your timing? Is it possible your carb is running too lean causing the overheating? I see you are in Lancaster, it has been over triple digits there the last couple of days. We are kinda neighbors, only about a hour away.

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Certified pilots, looking down on people since 1903.

Yeah I agree, you could be running too lean or your timing could be off.

Or you could have a head gasket or freeze plug leaking, or a blocked water route in the intake, head, or block.

I'm not loosing fluid. Not sre about my timing though. I'll check that as soon as possible. I have the original carb and I haven't done any adjustments on it. I'm the second owner and the truck had been sitting for a long time. I had it tuned when I first got it but that's the extint of it.
When I put the new thermostat and water pump in I didn't check the engine block for any blockage. But water did flow out pretty good when I hit the thermostat hole with an air chuck. My oil looks fine and I run 5W-30. I'm thinking about a carb conversion. But if I can't get this thing to cool down I'm done.

My stock carb is running lean. Do you happen to have the smog data, like the HC's and CO's? Will your truck run cooler when you run the heater with the fan on high? This info would help us get a basis and help you with the next move. See what your timing is at, if it is retarded it will run hot. I bought a 78 that the previous owner sold because of overheating problems, it was retarded 15 degree's. I retimed it and it ran fine temp wise. In fact that same motor is still running cool in another members truck.

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Certified pilots, looking down on people since 1903.

These readings are from last may:
HC (15MPH)-MAX=221/AVE=49/MEAS=217
HC(25MPH)- MAX=187/AVE=40/MEAS=101
CO (15MPH)- MAX=1.82/AVE=0.30/MEAS=0.09
CO (25MPH)- MAX=1.62/AVE=0.27/MEAS=0.23
I'll check my timing tomorrow!! I haven't ran the heater on high but I'll try it tomorrow.
Thanks for the help.

That is lean, but not enough to cause the overheating.

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Certified pilots, looking down on people since 1903.

My 76 runs hot on hot days and fine on cooler days It likes it about 65 degrees. I notice mine goes hot at an idle but comes down when you are driving. highway usually cools it down quick.

My 76 likes cool days too. But driving it here in SoCal keeps it warm all summer. I can't drive more than a few miles if it's 90 deg out before it goes above the middle position on my guage. I live 9 miles from work and that's about the limit I can drive it.

Has it ever boiled over on you? It could be the gauge and or sending unit. They all tend to have thier own attidudes. On my 78 it barely even moves off of cold, so if it gets past 1/4, I know somethings up. My other two trucks run right around the 1/4 mark so past 1/2 I would worry.

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OK, I'm over it. Where's the beer?

I've never had it boil over. But I don't drive it far enough for that to happen. I drive it to work and back mainly. Only about 9 miles.

Any one use an electric fan? IF so which one and where to get it? Mine is having the same prob. taking it to a carb gut to get it set right i cant get it right to save my life though. Got a water pump and temp guage, and new cap. Whenever i stop the truck is when my radiator over flows out of the cap.

I set my timing today. It was at 0 deg. with the vacuum advance plugged. I set it to 6 deg. BTDC with the vacuum advance plugged. This is by my shop manual. I'm going to put 20W-50 oil in. Does anyone think I should do something different or use a different oil? Again I live in the desert and it gets between 100-115 degrees here.

An old motor on hot days ,yes the 20-50 will work but when you start up let it warm up a couple of minutes so the oil will warm up an start to flow ,oh and the oil will raise you oil pressure by about 10 psi.

Try to locate a fan off a A/C truck as they have more blades to pull more air. I have one on my 80 4X4 and it stays right on the thermostat even with 100* days. These are a 6 blade fan some mount solid and some have a clutch.Speaking of witch dose your truck have a fan clutch and if so is it working proper?

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1978 pro street step/side 455Buick, 4sp,4.11s, 31/18.5s

I had the same problem with my 76 over heating on hot days. I took the radiator in and had them replace the two roll core with a three roll core. No more problem with over heating, even on 100 degree days.

I have a 4 blade plastic fan blade that mounts directly to the water pump pulley. I changed to 20W-50 oil today. I'm waiting on clutch slave & master cylinders from parts america. I haven't driven it this week because of my spongy clutch pedal. As soon as I can drive it, I'll know if the work I've done so far have made any difference in the overheating.
My next quick thing might be the temperature sending unit or the guage.
But, thanks for all the advice. I'm also in the middle of repairing the rust damage to my floor pans and bed.