454 cu Cooling Problems

EVarn · July 30, 2006

Need help

I have a 1983 454cu motor installed in a 1970 ¾ ton GMC Pickup truck. Confounding problems with the cooling or should I say overheating problems but not really boil over. The motor will remain at normal operating range as long as the vehicle is moving down the street and with the AC off. Lost at the dilemma I had the motor rebuilt, but it still ran really hot. The shop tried different water pumps for the 454 funny thing all of the pumps were too long to fit with out hitting the radiator that must be because the truck came with a L47 400cu motor according to the specification sheet that came with the vehicle. I replaced the water pump previously, we compared it to in-stock pumps at the auto parts store the only match was to the 400 motor. Checked or replaced all of the components that the pros have told me, such as various cooling Fans; electric fans, flex fan, clutch fan, new rebuilt 4 core Radiator, vacuum leaks, timing, carburetion. I was talking to a guy that said he had the same problem his remedy was something about the crossover in the intake manifold ? and that the timing gear alignment could be adjusted? Now this was quite some time ago I am pretty sure that is what he said. What are your thoughts, anybody that can help out with this situation will be appreciated.

redvett · July 30, 2006

What do you call overheating? The 454 is a big engine and will radiate heat. Normal operating temps should be 195 to 237deg. The 400ci is a small block and the 454 is a big block and the waterpump wont exchange. You must have the 454 radiator & shroud along with the 7 blade fan and clutch. There were short & long snout pumps available but efficency isnt any different. Any 396,402,427,454 pump are the same withexception of the snout length. The intake crossover is needed to heat the carburator when cold. Make sure the heat riser is working.

doverarjim · July 30, 2006

I did not see anything about a thermostat do you have one installed and if so what temp is it? Years ago when building big motors we had one that ran hot all the time and found that the coolant was moving to fast not getting cool enough in the radiator so it ran hot I do not remember now if we when to a 195 from a 175 or the other way around but that would be a cheap fix for you to try.

redvett · July 31, 2006

If the engine builder didnt put in a the thermostat shame on him. I can just imagine what the rest of theengine is like. :-(

EVarn · August 1, 2006

I'm new to these forums so please bear with me. The engine will (if at idle too long) become so hot that I don't dare remove the radiator cap I did once and learned my lesson there was coolant eveywhere luckely I had a large towel over the cap. it gets so hot you can't touch the fender. O.K. I know I'm supossed to keep a thermostat in the thing, only reason I removed it was I tried a 180F a 160F and a 190F it just got hot faster and I'd have to stop. the temp guage will peg. Could I have a goofy water pump on the thing? it seems to be pumping water through the radiator I look down the filler hole as I add water and can see it flow. How fast is it to flow? Really I don't know if it has the proper intake manifold or water pump. to keep it cool~The fan is a 6 blade direct drive factory if you will.

redvett · August 1, 2006

Never open the cooling system with engine running at operating temp. A 180 F will be fine for summer but check with another guage (use a heat gun). The fan should have a clutch and the blades must be no more than 1/2 way in the shroud to enable it to draw air through the core. Seal off the gaps at the radiator to enhance the ability of the fan to cool.

How much base timing do you have? Is antifreeze mixed no more than 50% (less is better) to get the max heat transfer out of coolant.

EVarn · August 2, 2006

I'll try to borrow a heatgun. The fan is mounted on a spacer that protudes an inch into the shroud, the spacer came w/ a FlexFan. Could I remove the fan & spacer, attach the FlexFan directly to the pulley, that's the only way I can see to position a fan to your recommendations? The clutch fan is long gone ? seems it was in the shroud also? Timing was set @ 4 BTDC. Have 50/50% coolant, less is better 40/60% maybe? I can do that. I used a water wetter awhile ago w/ min. results, for info only.

redvett · August 2, 2006

Do you have a shroud? The fan blade needs to be 1/2 way in the shroud for max efficency. Depending on the state / climate you live in but A/F is not the best heat conductor its water, read the water wetter instructions for mixture. Find out what hte running temp is. +4 deg is fairly good but check the sticker or service manual for the engine.

EVarn · August 5, 2006

I stand corrected the fan is not a 6 blade [it is a 7 blade] as was pointed out previously.

Yes there is a shroud, the fan is completely inside the shroud at approx' ¼" from the aft edge. The spacer is 1 5/8" which contributes to the depth of the fan. I sized two different clutches for the fan, I'll get the short one and install. The-idea of attaching the FlexFan directly to the pulley without the spacer isn't feasible do to the interference of the fan belts. I also noticed there is a gap of ¼" between the radiator and shroud on 3 sides. There is no heat riser on this engine. Timing per book is 4° BTDC. I run this truck in the Mojave desert.

1sep06 many events interfering with install. Thank goodness this is not my primary vehicle. My primary is a 2002 Yukon 4X4 5.3 which has been great.