i just finised rebuilding it and when i got it out and drove it it was running at almost 250 degrees. i have a 3 coar aluminum radiator in it, with aluminum heads, so im clue less why its so hot. any help would be appreciated thanks

 

Check these things:
1. Correct waterpump?
2. Air Dam in place?
3. Thermostat stuck shut, or even in place?
4. Fan working properly (If electric)?

 

If i'm not mistaken, dosen't a new rebuild or a new engine run hot for the 1st few miles? I have always been told not to run headers on a new or rebuilt engine for the brake in period because of how hot they run. if everything else if in working order it might be something to look in to.

 

Gauge correct? If it's not boiling over, it's not overheating. These gauges are usually far from accurate.

 

Im with camaronewbie on this one. The factory gauge is not reliable. Use an infared thermometer to verify temps at the radiator and thermostat housing. Check for thermostat openning by holding the top hose with your hand. You'll feel it swell and heat up when the t-stat opens. you'll also feel the radiator get hot and the fan(s) should come on soon after.

 

i have all auto meter guages in it and it is boiling over

 

So we're back to the basic questions not answered yet ...

1) air dam in place?
2) fans working?
3) thermostat working?
4) correct water pump in place and moving coolant?
5) this is the 350 in your sidebar?
6) carb or TPI?
7) what's timing set at?
8) single or dual fans?
9) stock fan wiring or aftermarket controller?
10) overheating in town, or on highway, or both?

so far all we know is that it's overheating - we need way more info. aluminum heads a radiator don't have anything to do with overheating.

 

No, thats not the case. The motor I built I ran with headers right from the beginning and it stayed at a cool 190* Constantly. That's not the probem.

 

the timing is at 8 degrees advanced
the water pump is fine
dual fans after market controled
its over heating in town and on the highway
its a .501 lift can with 244 duration on the int. and exh.
and its carburated

 

Factory carb? Has it been set up for the new motor? Running closed loop?

If not it's likely going to run rich and hot.

If it's been converted to carb the timing on your MECHANICAL, non-computer controlled distributor should be way more than 8 degrees advanced at idle. Retarded timing=hot.

 

So it's not just the gauge. I agree that 8 degrees is not enough lead for that cam. However, just in my own experience, I tend to find running more lead raises temp. I also find that running leaner raises temp. At any rate, whether you're running the factory carb or not, I would definitely get it on a gas machine and verify AFR. CO on that motor with no cat should be about 2.5-3% and HCs about 300-400ppm. If you can swing a wideband O2 that's even better. AFR should run about 12.5:1.

Has it run hot since you built it? Did you get the head gaskets right? Was the block boiled to remove all deposits from the water jackets? Does the coolant boil even when cold? That would be a head gasket failure. Check the cooling system, using the simple test I described above, to verify operation.

 

Agreed. Running too much ignition lead will cause an engine to run too hot just as running too little timing. An efficiently tuned motor (air/fuel/spark) will make the most power with the least amount of waste heat. Too much timing will have the piston still approaching TDC as the ignited charge begins to try to force it down. Late timing will produce an incomplete burn that is not used effectively for the power stroke-it will complete the burn past the exhaust valve. At the risk of oversimplification, of course.

A lean motor will probably run hotter than a rich one though as the unburned fuel in a rich mixture will probably have a cooling effect. At least until it burns up in the exhaust stream.