Chevy SB400 question-It's one HOT Chevelle

Hi folks

I've been listening to my husband cussin' all morning long at his car and thought I'd check with everyone here and see if you have any ideas on how he can fix his problem.

Bear with me....I don't know alot of the technical stuff. :smile: He has a '66 Chevelle with a SB400 in it. The engine was recently rebuilt and he put new heads on it last week. The problem is that it is running really hot...the gauges read about 230. It has been that way since he got the car. He's replaced the hoses, water pump, thermostat (twice..with both a 160 & 180), and flushed everything. It has a six blade fan that works just fine, but there isn't a shroud around it...would that help?

Any ideas on what else could be causing it to run so hot? ANY help would be greatly appreciated. The kids would like to take out their earplugs!

Thanks

a fan shroud what be good to have because of the density of the radiator fins...makes it difficult to persuade the fan to pull air though it.

also IF he's using an electric water pump those things are worthless at pumping water under pressure with good flow.

their could be a slim chance that the head gasket is blocking of some of the water passages to the heads.

but the first things you should check for is heat comming from the water line return to the radiator. if it feels hot then the thermostat is working.

large air pockets can get stuck in the heads, and can creat stem which will makes a larger air pocket.

But i'm just throwing out ideas... i'm not shure if their worth anything.

i couldnt tell you either but i do know that i have heard from a lot of people that 400s are known for having heating problems. Is it a big enough radiator to support the hp he has in it?

Thanks for the quick replys!

I'm going to print these out so he check everything the two of you mentioned. I hadn't thought about the radiator being too small. The car came from the factory with a 283 and it still has the original radiator. The 400 that's in there now might be a little much for it to handle. :smile:

If you think of anything else I'd love to hear your ideas.

id suggest an aluminum radiator from summit if you you need something cheap and quick.

Well, he's increased the displacement by about 40% and probably horsepower by about 100%. I would say that he needs a radiator that is capable of dissipating at least 100% more heat than before. Doubling the radiator's surface area is a good start. Chances are the original radiator's core is a two-row. GM used a four-row radiator in those cars in later years and the aftermarket is full of them. Its quite possible that the stock radiator is up to the task, just years of corrosion and gunk buildup makes it poor at flowing water and cooling. Perhaps a good boil-out and refurbing might be in order. That should cost under $60 if he takes it out.

Original radiators are made of copper and brass. A new aluminum radiator might cool better but there are things to consider. Copper and brass transfer heat better than aluminum, so the actual radiator metal itself is more efficient at getting rid of heat. Aluminum radiators tend to be more efficient overall since there is more flexibility with design. The tubes can be flatter and thinner which exposes more surface area to the coolant and the air. Before your cussin man goes and dumps $350 on an aluminum radiator, have him consider getting a $180 GM four-row copper/brass.

A good aftermarket flex fan will rob a few HP but it will move more air. A fan shroud is a must.

Changing the thermostat's opening temperature won't help. A car overheats because the amount of heat going in is greater than the system can remove. Even if you remove the thermostat it would just postpone the overheating for five minutes.

Also, 230 is not terrible. Its high and needs to be dealt with, but its not the end of the world. If it keeps climbing you might have trouble, but I would shoot for 210 or so. It sounds counterintuitive, but engines like to be hot, DRIVERS like them cool. Oil is happiest at 215-225. For the sake of detonation and other properties, 210 is a good medium. No cooler than 180, but I like 190-215 in street cars.