Thread: Big Block overheat

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I have BBC 454 0.30 over, 10:1. In a 1984 El Cabellero. Runs perfect, makes decent power throughout my RPM range. Here is the problem, cannot keep it cool in traffic. Have high flow water pump, Griffen aluminum radiator, high flow thermostat, 7 blade flex fan appropriate distance from radiator with a full plastic GM shroud. @ 55 MPH runs between 180-190. Get into a stop and go situation and its all over. It gets to 230 in a hurry, so either I have to get going or shut it down. I am not convinced that timing is the issue. I am having trouble remembering whether I set the cam @ 4 or 6 degrees BTDC. (It has been a few years and car set idle for a while). It has been advanced that water may be cycling to fast through the radiator. Any ideas?

Try somtin simple like, a colder thermostat.

have already tried range of thermostats have 180 degree presently.

Did it just start overheating? or was there something done to the car then it started?
First of all bored 30 over will make it run hotter.
Mentioning a colder thermostat might help. I can't see how that would help. once the thermostat opens it's open. You might have one that is sticking.
timing could be the problem.
One other question are you running hot or boiling over?
Also you might check the radiator cap the seal might be torn. what is the lb cap your running?

The engine has ran hot ever since it was put together. The radiator cap is made by Griffen for this particular radiator, and it is in perfect condtion. I have tried adjusting the timing slightly, after I placed a new MSD ignition system in last year, didn't really make any difference. It does get hot enough to flow into the overflow tank, but I never let the heat get out of control before shutting it down.

Try 40 below from summit, it says that it will drop coolant temps up to 40 degrees, it also recomends that you use it with str8 water ( not in winter ), I would recommend using distilled water instead of plain tap water but, that's me. It will work with coolant as well. It's $24.99 a bottle and takes 1 bottle so, it is a little expensive but, it's not going to break the bank. Run a pusher electric fan along with a 17" flex fan on a thermal clutch, might help to.

Friend of mine runs a 454 in an ElCamino at the track. He uses an electric water pump. Says he has to shut the pump off sometimes in the staging lanes to get engine up to temp before a run. Drives it on the street too.

Is your Tranny cooler or air-conditioning core in front of your radiator? if you have these blocking off your radiator, it wont work 100%

BACK TO TECHINSPECTORS POST...
Check the fan blades closely, they have to have the back half out of the shroud and the shroud should have a good seal to the radiator, you fan pulls air in from the center and pitches it off the ends of the blades so if the blade is inside the shroud your just stalling the air, also power pulleys or small crank pulleys can slow the fan & water pump down........

I certainly understand the OEM approach. But it failed. Like I said I have the Stock shroud, correct size radiator and fan. I tried the OEM route first... stock pump, clutch fan, 4 core copper and brass radiator, only when it failed did I go to aftermarket parts to try and correct the problem. The powerplant is by no means stock. Your suggestions are greatly appreciated. I will defintly reevaluate fan depth.

Like Techinspector, I live in AZ (fortunately a little cooler part, it only gets to about 110 here in the summer).

Under the conditions you describe, I tend to agree that the problem is lack of airflow at low speed. My cure in the past has been to use a good 7-8 blade fixed fan with a fair amount of pitch and the heavy duty (about 2 inch thick and twice the price of the standard duty) 454 Truck clutch. They roar a little at speed when they lock up (when the engine starts to heat), but it usually cures the problem.

Originally posted by Cabellero
I certainly understand the OEM approach. But it failed. Like I said I have the Stock shroud, correct size radiator and fan. I tried the OEM route first... stock pump, clutch fan, 4 core copper and brass radiator, only when it failed did I go to aftermarket parts to try and correct the problem. The powerplant is by no means stock. Your suggestions are greatly appreciated. I will defintly reevaluate fan depth.

Well, I have a cooling problem in my motorhome, P30 chassis, 454. It gets hot real quick when sitting in traffic. I have elec fans in front of the radiator, but the AC condensor is still mounted there also, which I think is blocking airflow. The AC has never worked anyhow so this is the first thing I am removing. My clutch fan is stock but seems to be quite a ways from the radiator. The blades are 1/2 in 1/2 out of the shroud which seems to correct??? I will be installing external oil cooler and trans cooler also. Just trying to keep the temp from going over 1/2 way hot so quickly...I can see how pulling a hill might do that, but sitting in line or traffic, gets scary.

Stop recycling hot air, you can fab up a lower air dam out of 1/4" x 5" rubber, did'nt use to be OEM but is now...........

An engine oil cooler will work great I have a oem cooler on my 90 chev pickup. if the motor still runs that hot it might be a crack in one of your cylinder walls. A friend of mine with a 350 bolted into an s-10 had the same problem. When he finally broke down and striped the motor down he found a hairline crack in one of the cylinder walls! Hope thats not your problem!

i used to have the same problem with my rat i changed my fan clutch from a thermal 454 unit to a nonthermal 327 clutch. it did the trick.the stock ones tend to wait longer to lock up usually around 210 220 by then its too late most the time. the smaller one will lock up much sooner, or you could just invest in an electric fan system like i did so much cooler.....hope that helps ya any good luck