I am posting this for a friend that just rebuilt a 396, 30 over, mild cam. New 4 core rad, remaufactured water pump, new rad cap, Prestone 50/50 with water. The engine is running hot, it huffs a little blue smoke when started for a minute or 2 then stops. It only has about 5 miles on the re-build as he is still restoring the car so it has not been broken in to any degree. He has tried a 180 and 160 degree Tstat and most recently removed the Tstat to no avail. Once he turns off the car it really heats up.

He talked to the the guy who built the engine and he is suggesting using electric fans which he really does not want to do that.

Any insight on how to resolve this would be appreciated.

Thanks

Does he have a fan shroud installed? And what kind of fan set up does he currently have on the car? These items can make a difference. A new engine can run hotter during break-in.

I was using a factory replacement 4 core radiator, shroud, clutch fan, and stock water pump on my mild big block and it ran hot in traffic or at idle. I changed to an alum radiator, Edelbrock Victor water pump, Derale 17" fan and now have no problems with overheating.

Timing that's retarded and/or a fuel mixture that's too lean will heat up a motor. Also, if you're running a factory exhaust, check that the exhaust pipe valve behind the passenger's side exhaust manifold is not stuck closed.

New motors run warm though.

What you may do to get her broken in, is open the drain cock located at the bottom of the radiator to allow warmer water out while you refill the radiator with cooler water from a garden hose, while you run the engine for break in.

Let us know how it goes.

it is common for a fresh rebuild to run a little hot from what i was told. if it was rebuilt professinaly the engine was proably dippied and water passage are clean pop the radiator cap. check to make sure water pump is working squeeze the hoses to belch out any trapped air. check timing. the fan shroud is very important. and is needed to pull air properly through radiator. he should also look into having radiator rodded out. or replace it with new 4 core. radiators at autozone shouldnt set you back more then 300 dollars just get the heavy duty 4 core. cars tend to always increase in temp once you shut them off. the reason for this is no water circulation so the engine water sits stag and warms up. that is normal nothing you can do.

I can't see how we really can give any advice without knowing more info. Did the cam get broke in without it getting too hot? How did the 5 miles get put on the engine? How hot is the engine actually getting? Have your friend put the 180 stat back in and stop trying to fix anything without collecting the necessary data first. Changing stats in a over heating engine is not doing anything as once the temp gets above the rating of the stat it won't close... How long will the engine idle without the temp going to 210 or above? Does it get hot on the hwy too? Let us know I'll look back for a response...

I had a simalar problem with a new engine ,carb .... I found it actualy was boiling the fuel in the carb and dumping it into the engine when I shut the engine off , mostly in the real hot weather it would then let a little blue smoke on start up. It was just a little lean 1/4 to 1/2 turn out and no more problems.

Just a side note here.. I have a 396 30 over in my car with a dual plane intake and 850 cfm, at trans, 3000sp converter, headers and i am running a factory 4 core rad with a factory clutch fan and shroud with a 160 thermo and i never have a problem, Even when its 90 outside so i really dont think its a rad problem.

How hot does it get?
Are the hoses hot to the touch?
Fan belt tight?
Is the fan clutch working?
Are there a min of seven fan blades?
Is the shroud in place?
Is radiator exhaust air recirculating back through the front of the radiator?
Does he have a high flow thermostat installed? MRG-4364?

An overbored block and new engine internals will run hotter, especially with a lean fuel mixture. Try a 40% af to 60% water mix, water by itself is the best heat transfer agent.

Car only has min mileage as it is still under going restoration, a couple of times around the block and such. It has a new 7 blade 18" clutch fan, and shroud, loosened off a plug on the intake to make sure it was not air locked. The temp climbs to the point it is ready to over flow the rad, according to the gage 215F - 220F. This is in 60F outside air temps. Cam was broken in on initial start-up 30 min at 2400RPM.

I woulkd guess retarded timing too... but I'd seriously have to ask what kept it from lookinglike Mt. St. Helens running 30 minutes @ 2400 sitting still to break in?

Maybe that was before the timing was set to "spec"?

I just want to add that you guys are an engine builders worst dream :( Leave the engine alone, dont even turn the key, until you can drive the car for at least a couple of hours straight. Finish the restoration, then fix the cooling problem. Constantly starting and stopping a new engine is absolutely the worse thing you can do to it. If it's getting that hot, that quick, something is wrong in the cooling system. I have seen engines with terribly retarded timing .... the headers are cherry red, but the cooling system is still working. You need to get an infrared temp gun and "shoot" the radiator etc and see where the heat is going.

I will have him take your advise and leave the bloody thing alone until the resto is finished and he can break it in properly. Once thats done, and with the timing set correctly, he can better diagnose the problem if any.

I just want to add that you guys are an engine builders worst dream :( .

But bill..... that's why we do the engine first.... when all that nasty stuff get's us down, twist the key and make some noise for a few minutes, get the head straight again!

'course, you are tooo right.