my 87 camaro has a big block chevy and i can't get it to cool. the motor is a '72 427 tall deck stroked to a 496. the car overheated at 250+ after driving for about half an hour. i stopped for gas at 210 and it shot up to 230, and by the time i got to where he was going 10 minutes later it was at 250. the car has a griffin aluminum radiator, 180 thermostat, 2 cans of 40 below coolant additive, permacool electric fan (3000 cfm) and a stock flow water pump (brand new). the car had a high flow pump on it when it overheated and i thought it might be flowing the coolant too quickly to let it cool off but the car does the same thing with the stock pump. the pulley ratio slows down the pump a little, too. i checked for air pockets and put an electrical and mechanical gauge in the intake. it takes the normal amount of time to get to 180-190, but from there it climbs up gradually to as far as the gauge will go. the timing is at 26 degrees and i haven't had a tune on the carb yet.

i can't find anything anywhere, but was there a reverse rotation pump on any big blocks? i can't find the stock pump to check the impeller, but something is definitely wrong.

ANY ideas? the car won't cool no matter what is done...every part of the motor is brand new, nothing used.

a headgasket that leaks a tiny little bitsy bit will make it overheat just a tiny little bitsy...

i had rtv on my old headgasket..........

Are you sure there is no trapped air in the cooling system? Has it been bled? You mention under driving your water pump, this could be a problem also. I have a BBC camaro, but I overdrive my Stewart hi flow pump, I switched the stock 6.3" water pump pulley for a March 5.5" pulley just to turn my waterpump that much faster. Its an old wives tale that the coolant will move to fast through the system to reject heat, the opposite is actually more desireable to flow the coolant as fast as possible, under the highest pressure your system will bear.
A hi flow pump generally requires a hi flow T-stat to be able to handle the extra flow from the hi flow pumps.
I don't have A/C on my car, but do have a heater loop, so I blocked the water pump bypass, which will force more coolant through the rad. indstead of it going around in circles, this also helped keep my BBC cool. This can't be done to an A/C car as the coolant path is blocked through the heater core when the A/C is on. There must be some sort of bypass to allow flow until the T-stat opens.

"Timing is at 26 degrees" WHEN? That's too much for initial, and too little for total advance. How much vacuum advance do you have? Not enough advance can cause overheating, not enough vacuum advance can cause overheating during part throttle cruise.

How does it run? If it runs good, your fuel mix is "probably" good enough not to cause overheating. You still need to verify that, though.

Collapsing lower rad hose?

What pressure cap is on the radiator?

What head gaskets are you using? Although I don't get feedback on this, I say chronic overheating on a BBC can be due to incorrect-for-the-block head gaskets. NOT all MK IV big blocks use the same coolant circulation pattern.

I have a strange fix that has worked in 2 big blocks that I have run and a friend's car as well. I'm sure there's going to be opponents to this, but for less than $5, it may be worth a try. Drilled 3 small 3/16 holes 120 degrees apart on the thermostat and removed the manifold bypass line to the water pump(this allows some bypass without creating a vacuum).

The other suggestion is that 3000 cfm is not a whole lot of air flow for a big motor like that. I'm sure you are limited on space, but I wouldn't use a 3000 cfm fan on a small block stroker.

Mike

in an 87 Camaro, if you don't have all the air dams and other curb grabbing stuff under the nose of the car, you won't get enough airflow thru the rad to keep a stock 305 cool- let alone a tall deck big block.
have you tried going for a cruise with the hood removed, to see if you just need more airflow thru the engine bay?

all of the plastic **** is back on the car and it didn't seem to make any difference. it won't stop raining here, but i'll play with the timing and bring it up around 34 when it does and see if that makes a difference. the hose is ok and there are no bubbles in the system, so i'll give the timing a shot.

i do appreciate the help, and all suggestions are welcome. thanks!

hold the rpm at 3000-4000, THEN set it to 34 degrees............

You didn't put the T-Stat in up side down? Did you...

I have to admit I've been guilty of that ONCE..

AND yes, drill a couple a small holes to help her burp!!!!!!!!!!! I hate taking 20 to 30 minutes to fill a radiator!!!!

pdq67