Q: I own a Chevy Impala with a 468-cubic-inch big block Chevy engine. It has 12:1 compression, Crane 298-degree duration cam, oval port cylinder heads, 926 cfm Holley double pumper on a Holley Strip Dominator intake, and an HEI distributor with an MSD ignition. The transmission is a Turbo 400 with a 3,500 stall TCI converter. The rear-end is 12-bolt with 4.88 gears. Total timing is 38 degrees, and the car weighs about 3,200 pounds. I have an electric water pump drive and am using block filler. I have only eight runs on the engine, and all parts were checked at the machine shop before the engine was assembled.

My big problem is that the engine doesn’t run well unless its temperature is between 190 and 210 degrees; at 225 degrees, it overheats. Should I run an alternator and fan off of the crank pulley? Can the block filler (tall fill) be causing a problem? What else can I do to cure this?

1970 chevy impala coupe rear quarter shot
(Image/OnAllCylinders)

A: Your engine combination sounds good. Your power loss could be related to your cooling system problem. Even though you only have eight runs on the engine, a cylinder leakage and block test would help determine if you have a bad head or head gasket, or a crack in a head or the block.

If these check out OK, look at things like valve adjustment, carburetor jetting, and ignition timing. These can have a very dramatic effect on performance, and could be the cause of your overheating.

Yes, you should run the alternator off of the crank pulley. If you use an electric fan, get the biggest one that will fit the radiator, and get a manual fan switch so you can turn it on before the engine gets too hot. This will also allow you to run the fan and the electric water pump in the pits to help cool the engine between rounds. The block filler should be fine as long as it was installed properly. Since you used tall fill type block filler, you may want to check to see if it is blocking the water pump inlet holes in the front of the block. If it is, that means coolant cannot circulate through the engine.

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