I have a stroked out 383 with Vortec Heads and the intake, runners and plenum are all Edelbrock. At idle I can get the engine up to 210 degrees and the first fan kicks on and cools it off about 10 degrees and shuts off. But while driving it cools off to 160! It has a 192 degree thermostat that I know is working correctly and the fans are not running. I have an induction style hood scoop that is open in the rear and I have done away with the factory oil cooler lines and even plugged the coolant line that goes to the heater core diverter valve so there is NO coolant flowing through those lines. How does an engine like this run so cool? Does it have anything to do with the Vortec heads? I am thinking about blocking off some of my radiator but when the car is driving down the road at 160 - 170 degrees there shouldn't be any coolant flowing through the radiator!
I know the gauge is reading fairly accurate because the car doesn't run as strong when it is showing the lower temperatures. If I sit and let it heat up, it runs like hell!
Any ideas are surely appreciated.

 

possible the tstat isnt closing fully when it cools off.

 

Even with a T-stat there is always fluid flowing thru the system. Just not as much when T-stat is fully open.

If your cruising at 160-170, I'd say thats a win win. Nothing wrong with running cool.

Tune shouldnt change with temp if it was tuned correctly. Most motors run strongest when cold, its a popular trick by dyno operators selling crate motors. They run ice water thru the motor when dynoing. Usually shows more power.

 

Throw a new cooler t-stat in, if you are cruising at 160-170 than your 192 t-stat isn't functioning properly. Get a good T-stat and try that. If it's just an issue with building to much heat idling, then look into an aluminum radiator with dual cooling fans.

IF it's not getting hot enough, then it could be the hood is letting to much air circulate. But if it's getting that hot at idle, and that cold while driving, sounds like a crap t-stat to me.

 

id say 170 is about the lowest temp you want to run for engine life. while colder is better for power, too cold leads to premature wear on engine parts.

 

I agree with travis, 160 degrees is NOT a win situation and the motor does run much different at that cool of a temperature. Can someone explain to me how water is circulating when the thermostat is closed? When I take the thermostat out and it is at room temperature, the thermostat is closed tight. The reason I ask is because I was wondering if when the stat is closed, maybe there is no water reaching the temperature sending units in the Voretc heads? I know Vortec heads are supposed to have reverse coolant flow and these do not because they are on a non-vortec engine. I am at a total loss.
I have had two different thermostats in this car with the very same results.

 

it flows from the bypass next to the waterneck, through the heater core, and back into the rad.

 

A T-stat is not a perfect seal. Even when closed, it will pass water under pressure from the pump. A trick most guys do is drill 4 small holes in the outer ring to allow more water to pass thru while its closed. Usually used to help with cooling but you seem to have the opposite problem.

Water is flowing because at driving speeds, the car is cooling down. Air must be passing thru the rad and cooling the water and that cool water goes into the motor keeping it cool. If it didnt you'd get hot spots in a hurry.

Vortec heads are reverse flow? I didnt think they were, since LT1's are your typical reverse flow and those heads will NOT work on a Gen I sbc without plugging the ports on the head. I've never heard vortecs being reverse cooled, and know guys running them in the past without any issues. I dont think its your heads, you just have too much cooling capacity at cruise IMO.

As long as the oil temperature is in a good range, i dont see how being 160-170 deg will hurt engine life. As long as the oil is doing its job in providing lubrication to parts, nothing should be hurt. Yes too cold is a problem but 170 isnt that cold. Its cold but not like a cold start on a cold day.


Who did the tune on the car? Perhaps its low on timing and rich, making cool chamber temps? Running poor when cool sounds like the fuel tables are off in the coolant temp based fueling tables. It should run as strong if not strong when less heat soaked

 

Travis, I blocked the bypasses off but thanks.

Orr you are correct about the reverse flow, I was thinking LT1 again. I am sure the tuning could be better but I am still stumped how an engine putting out good power, running high revs, COOLS down while going down the road. I am not arguing with anyone..... just scratching my head. It cools down when I am running it HARD and to have it drop down to a temperature that much below the setting of the thermostat just baffles me..... I have seen a lot but never this. I am going to block off my radiator and see what changes. Do you think tuning issues would allow the car to run so strong but be bad enough to make it run too cool?
I was wondering if somehow the hot water is not getting to the sending units until the thermostat opens. That possible?

 

Do these vintage computers have open loop and closed loop? I know the newer ones do and a certain temperature must be reached to go into full control "closed loop".

 

Really need to measure the temps at various places. If you can verify sensors and sending units are good then thats a good start. It does seem odd to have such good cooling at speed if running it hard.

Whats the ambient temps? Where you located? Perhaps cold air outside is creating some of the problem.

If it runs hard when hot, then the tune could be spot on at that point, but the fuel tables can be overly RICH when at cooler coolant temps...thus losing power. Need a wideband o2 to verify fuel mixtures. Some motors like being hot tho, get better atomization of fuel on hot valves. Possibly better burn in hotter engine chambers.

Edit: yes they have open and closed loops. Open loop has a coolant based table that will affect fueling. Same with closed loop tables with PE mode enrichments.

 

I think mine drops down so much in temperature that it actually goes into open loop and it just doesn't run as efficiently in that mode. I am not saying the car runs HORRIBLE at lower temps but it runs stronger at a higher temp of 190 - 220.
As far as ambient temperature goes, I live in LAs Vegas! Pretty warm.

I am thinking about putting an electric water pump in and using temperature to adjust the speed of the pump. Higher the temperature, faster the pump. If it hits 100% speed and still gets hotter, the fans will kick on. I am thinking this would work quite well even with no thermostat. Anyone ever done this. I am a process controls guy and love these types of problems but HATE just going around in circles making no headway......

 

CLosed loop on these cars is usually set at a low temp, like 104 deg F. What can happen is if your exhaust cools too much and cant heat the o2 sensor, it will drop out of closed loop occassionally. I think your air fuel ratio needs monitored to tell for sure if the cooler temps are changing the fuel the motor is seeing.

My motor runs on electric pump full time. No speed variation, no thermostat. Runs hot all the time with no fans on. 200 deg with both fans on in the hottest days. Can hit mid 190-200 at cruise with both fans on, on hot days but generally has been in the low 180's. Not to bad.

Colder air, it will dip down to 160's cruise with both fans on so i just keep 1 fan on. ~175-180 depending. My car is turbo'd so the underhood temps get very hot and so does the oil, so the motor is expected to run hotter.

If you go electric pump it can create some problems with accessories. My solution was march pulley kit for electric pumps. Pretty fancy but expensive at 550 or so. Wouldnt recommend it as a solution to your problem but its your decision. Its a nice looking kit atleast.

If you do this I'd leave the electric pump on all the time and focus on fan control to get the temps in line. I dont think an electric pump flows as good as a conventional pump so it may run hotter with just the pump.


Quick fix you can try is remove the air dam under the nose if you havent done so already. SHould stop air flow into the rad. Should heat up quick

 

160 deg water temp is just fine on these cars ESP w iron blocks. Its the oil temp you want to keep warmer.
Taken from another source. Minimum running oil temperature: 200 degrees. Maximum: 260 (synthetic), 240 (mineral).
Even at 160 water your oil temp will b 200plus (ish)..

 

When I say 160 degrees, I mean TOPS at cruising speed and the temperature fluctuates way too much for me. I can see as low as 140 while driving and 220 while at idle. I know this is not right so I want to fix it. Yes 160 may be OK and 220 may be OK but the fluctuation is crazy. I think I will try blocking some of the air, then maybe restricting some flow, etc at least until I can make a change and then go from there looking for a permanent fix. I am shooting for an operating range of 190 - 200 which is what a 192 thermostat should do. Thanks everyone and if anyone has any more ideas I sure would appreciate it.

 

Success! Thanks everyone, especially Orr89. Removing the dam under the car was just what the car needed. Apparently when you run an open back hood scoop it makes that dam MUCH more efficient. Here is everything I did to get he car running PERFECT!
Removed and plugged the OEM oil cooler lines.
Pugged the recirc line that bypasses the heater core when not calling for heat.
Installed a high quality 192 degree T-stat.
And finally, removed the dam.

The car heats up to approx 210 in a reasonable amount of time and then runs between 195 and 210 constantly....

Now for a REAL oil cooler (i live in Vegas) and lay down some 1/4 mile runs!

THANKS everyone.

 

Glad you figured it out If it ever gets too hot, just reinstall the air dam.

 

Exactly. I think it will be OK though, we will see! Now if I could only get the thing to find a little GRIP at launch..... Another project.

Thanks again

 

Boy am I confused now. Every other thread on here talks about how hot these cars run. Many are running hot because the air dam is removed. This one, however, needs the air dam removed to run normally? Something doesnt sound right.

I am glad it appears to be fixed, but have you checked the calibration of the water temp guage?

 

It doesn't "appear" to have fixed it, it did fix it! All cars are different and mine is far from stock. You need to compare apples to apples and not group all third gens into one basket. Mine is stroked, vortex, huge four core aluminum radiator, open back hood scoop, different compression, different cam..... Etc. All this makes a difference. Plus tuning makes a difference too.
About the temp sensor, first yes I have check calibration. Second, it really doesn't matter because the trend of the changes is more important. Same sending unit giving different results is something you want for feedback.

Unless you are talking stock vehicles, be careful when talking about typical problems and fixes. My car does not have many stock parts on it.

 

That engine should run hot...

But with a huge 4-core aluminum radiator and the hood scoop. That would explain it.

Keep an eye on the temp gauge when it starts warming up again this spring/summer.

 

You bet I will, definitely not throwing that dam away! I am hoping the two huge electric fans will do the trick this summer, if not, back to the dam.

 

Does your heater hose run to the pass. side of the radiator? Thats where it might be cooling off at, being the rad is all aluminum.
Another way to test the temp is hook up a scanner & read the live data.

 

Yes it does and when I wasn't calling for heat, the recirc would run lots of water though all that hose and get cooled off by the air being forced up through the engine compartment by the dam and the open back scoop. What a freakin difference! I just got rid of all the recirc and oil cooler stuff and went back to basics. Sometimes trying to get 100% out of an engine 100% of the time just causes so many problems that the engine NEVER runs 100%. I am a firm believer of the K.I.S.S. method.

 

You didn't indicate that you had a four core alum radiator in your first few posts so I didn't know. Also, I did not know a functioning hood scoop could make that much difference. Guess I learned something. I also wasn't grouping all third gens in one basket...I just happen to know from experience that these temp guages are known for being out of calibration and that these cars, in general; modified or not, tend to run on the hot side, so I wanted to offer the suggestion to you that you might want to make sure your guage was accurate. Just trying to help. Glad you got it fixed.

 

I didn't mean anything by my reply.... sometimes typing doesn't bring out the intent of what is being said. All replies are GOOD! I had no idea an open back scoop made that much difference either so those of you that are getting hot while cruising may want to look into this! Also that open spot makes a nice spot for a shift light and gas pressure gauge. Peace all