Okay, 72 Nova with a fairly built 355. The tranny is a 3 speed auto and the rear end has 4:11 gears. At 65 (or so) the car turns about 3000rpm and it begins heating up. It gets to about 200-210deg which is more than I care to see. It actually runs cooler (190 deg) at 45-50mph or 2000RPM. This is with a temp of 95deg outside. It doesn't have any problem with overheating at idle though. After a run on the highway it does overflow just a bit, maybe 1/2 a pint total.

Any ideas? I'm running an electric fan and the radiator and water pump are new. I've been thinking about a bigger radiator and maybe dual fans.

Thanks!

270win

Since it runs hotter with more speed fans are not at issue. The fact is at higher engine speed you are pumping in more heat and the radiator can not shed the heat quickly enough (either that or your water pump is going into cavitation and not pumping the water at higher speed). You say the radiator is new but failed to describe it. Is it a SBC version of the Harrison copper-brass radiator with two cores, three? You may need the BBC version three inches wider, with four cores or go with an aluminum two core in BBC size with a 1.25" tube size.


Big Dave

The radiator is an SCB copper/brass 2 core. I've been thinking about the 2 core aluminum BBC and possibly an upgraded pump.

What's been working well for you guys as far as radiators and pumps? The pump is serpentine belt driven. Will the BBC radiator bolt right in or will I need to do some additional modifications? Also, I really like my engines to run in the 180deg range. I'm assuming that's warm enough.

Thanks!
270win

BBC radiator drops right in. You may have to knock out three inches of core support but it is already perforated (scored), you just have to break it out. Yes if you have a two core SBC that is your problem with a hot 355. Aluminum will definitely out cool a brass radiator, and a BBC is bigger than a SBC radiator (longer) so it will be better for the street. I would leave the water pump alone until it fails in service at some time in the future, then replace with a Stewart Stage II (or Stage III) or Edelbrock high flow aluminum one. By the way a generic radiator is patterned after the Chevy cross flow for some strange reason so it will cut your cost of an aluminum radiator in half if you do not mind fabricating mounting tabs and installing a transmission cooler in front of the radiator.


Big Dave

Do you have the correct water pump for the serpentine system? The GM factory set up turns the water pump backwards of the standard V belt rotation. So a sepentine specfic water pump must be used with an impeller designed to flow the water in the proper direction thru the engine with the rotation of the belt. If not a GM set up check with the manufacturer of the system for the correct water pump. I have also seen rebuilt pumps with the wrong impeller installed.

Dave,
I'll be going BBC aluminum for sure then. I'll probably just go ahead and install the Edelbrock pump as well. I like heading off as many future problems as possible. I'll also be installing a cooler thermostat. Is 160 asking too much of the system in 95deg weather? I've always heard that cooler is faster.

Philip,
Good question. It is the correct pump though. It works just fine below 90 degrees outside, but any warmer than that and you've gotta take it easy.

270win

In my personal experiance i do not like running a 160 degree thermostat,the reason being is once the motor gets to 160 degrees u might as well just have a restrictor plate in there,(because the motor will never drop down below this allowing the stat to close)wich i have run with some success in higher compression applications,i run a pretty wicked 383 in my car,and i run a 200 degree stat,the reason being is when the stat is closed untill it reaches 200 degrees it allows the coolant thats trapt in the radiator to be cooled longer,there for once the stat opens the motor drops down in temp and just kind of cycles with in 15 degrees,this has always worked well for me,i also run a griffin alluminum radiator also.another thing that i was always a stickler on was making sure your fan setup is properly shrouded so your pulling the most amount of possible air across the radiator,if your running going to order a new radiator,companys such as derail,cool,and flexalite offer packages wich the fans that are custom fit to the radiator giving you maximum amount of air flow,because i'll tell ya getting em hot all the time deffinetly takes time off of their clock--Dan

I totally agree, heat will wear one out quickly. That's my biggest concern. Fortunately this has only happened once and it was only about 3-4 minutes total. The temp got to 210-220 degrees so I think I'm okay.

That explanation makes perfect sense, let the radiator cool the fluid while the engine uses what's in the block, then exchange the cooler for the warmer coolant...But if there's no time for the radiator to cool the fluid then it will actually run warmer, even with a cooler thermostat. I think Big Dave posted that somewhere else too.

I'm running an electric fan with no shroud. There is no engine driven fan in this car.

The next question is, how hot is too hot? And what thermostat to run? It has a 190 in it now. Bottom line, I don't want any issues with it. I'm about to have the A/C hooked back up and I want it to run cool all the time. Cost is not really the issue. I'm not saying that money is no object, but at this point my biggest investment is in that motor. The cooling system needs to be up the job of keeping things cool...

Thanks!
270

You have to try selecting a thermostat that allows your engine to run in as tight of a temperature band as possible. Heating and cooling causes thermal expansion and contraction. Forged steel and cast steel do not expand and contract at the same rate, but they are close and if this is all that is in your engine it probably wouldn't hurt anything. Now you start throwing Aluminum, brass, and stainless into the equation you can start to have issues. Due to the size of journals and such in an engine all this is minimal on an engine, but over years of use could lead to a problem. The stuff I deal with at work are bearing journals of 4 feet diameter or greater and we are only allowed 5 degrees C temperature differential on some of them before the hole unit starts sending alarms. If this differential gets to high you start wiping bearings. At over 100 K to overhaul these bearing pedestals thats not a good thing.

The type of thermostat used will also make a big difference. I have a 79 Turbo Regal. The little six would constantly run hot. I installed a V8 radiator, electric fans, shrouds and all to no avail. I was advised to change the style of thermostat and the problem would go away. I wasn't convinced but really had nothing to lose by trying one. The engine never ran hot again after the change. I removed the electric fan and went back to a stock clutch fan and shroud and it still runs right at 190 even with the A/C running, in city traffic in the Arizona desert.
The thermostat I purchased is a Robertshaw unit. Mr Gasket also sells the same one under their name. It opens and closes smoother and keeps a tighter temp band.

http://i80.photobucket.com/albums/j199/64elcamino/thermostat1.jpg

http://i80.photobucket.com/albums/j199/64elcamino/thermostat2.jpghttp://i80.photobucket.com/albums/j199/64elcamino/thermostat3.jpg

So this may be as simple as a thermostat change?
I suppose I should try the least expensive thing first. Maybe a hi flow and more precise thermostat would do the trick.

I never thought about the difference in the expansion/contraction rates of the various metals in an engine. Mine has it all. So again, how hot is too hot? 190,200,210,220?

270win

My sons 94 Firebird with an LT1 has a factory setting of 230* before the electric fans kick on and there is no belt driven fan. IMO that is to high but the car has 160K miles on it and still runs good.

The guy who built the engine says 200-210 will not hurt it. But I agree with your opinion, that just seems too hot to me. I'm no longer worried about the other day when it got to 220 though. I'll get the new thermostat tomorrow and try that first. I've been wanting a chrome thermostat housing anyway so this is a good time to install that.

I'll post the results tomorrow.

270win

I raced stock cars on dirt for years,and we ran 12.5-1,13-1 compression motors every season and as you may know compression equals heat,that said we tryed to run the car between 210-230 degrees this will not hurt the motor the only problem is that over 230 and u start to hurt the motor,so when in that range being so dangerously close u want to have your cooling system figured out,the hotest i've ever got a race motor after running 30 laps in 95 degree heat was 280-this happend 5-6 times and the bassement blew out--so not to add too many thoughts and confuse u on the question, in my honest opinion a good operationt temp is between 200-220-Dan p.s.- if u dont run a gauge just wait untill u can smell hot coolant/rubber smell, then its to hot---lol:D

Thanks Dan! LOL! I'm trying to avoid the hot coolant/rubber smell... :-)

Based on everything here, I guess I'll stick with 190 then. I'm off to the parts store...

270win

Okay, so I switched out the thermostat. It was a 160 degree and the electric fan thermostat is 190 degrees. I installed a 180 degree MrGasket just like the one above. No change, it actually got hotter.

I'm installing an Edelbrock hi-flow pump and an aluminum 4 core BBC radiator tomorrow. I'm also changing the fan thermostat to 180 degrees. If that doesn't work I have no idea what else to do.

270win

What a LONG day! The pump the chick at the parts store sold me was the wrong one...not reverse flow for the serpentine setup in my car. It didn't even come close to fitting thank goodness. It would take them a few days to get the right pump. They also didn't have the right radiator and that too would take another few days. I had the 3 core that was in the car flow tested and it tested perfect. So I bought another thermostat (195degree) to try out. It was even worse. I pulled that thermostat and gutted in by cutting the spring and removing everything. It's basically a poor man's flow restrictor. It works like a charm. The car will idle all day and stay at 195, run it in traffic and it's 195...highway driving, 195. I'm sure I'll have to re-address this when the weather starts to cool.

But the bottom line is, I'm ready for Friday night at the drag strip!

Thanks for all the advice and input.

270win

Yours is the first case I have heard of having temps run cooler with a restrictor plate rather than a thermostat. Bottom line is you have to go with what works. :thumbsup:
BTW I use a gutted thermostat on inital engine starts to avoid the possiblity of one sticking and ruining a cam break in.

You're right! What ever it takes to get the car running at normal temps.

When I go to add a thermostat this fall I'll install the aluminum radiator and hi flow pump.

270win

I just went through this nightmare on my 72 Nova. When I first got the car it would not go over 160* for nothing. Then, a few weeks ago, the temps would climb to 210-220 when I was driving for only a mile or so. I bought a new stock pump, 3 core rad from Advance Auto Parts, and a 160* Mr. Gasket thermostat. To my suprise, when the radiator came in, it was an aluminum unit with plastic tanks. I was expecting the replacement to be copper but I was happy I got an aluminum one. The only thing I don't like are the tanks...oh well. Anyway, after driving the car today, it runs around 170-175*. My car has a stock motor in it though and a highway gear, probably 3.08s. Good luck with your 72.

That may be a good way for me to get an aluminum radiator for less money.

Glad to hear yours is running cooler now.

Brandon