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post #1 of 24 (permalink) Old 05-18-2019, 04:41 PM Thread Starter
 
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Engine temperature

Hi everyone. I need your opinion about something. I know there have been numerous threads in the past about engine temperatures, but this one might be a little different. I have a '71 GTO with the factory 400 motor and drivetrain. TH400 trans and 3.55 posi. I'm running a 180 degree thermostat, have a shroud, I think I have the divider plate in the waterpump correct, a spring in the lower radiator hose, new fan belt and a new Cold Case radiator. When I initially start the car and begin driving it, it seems to take some time and several miles for it to reach operating temperature. It gradually will reach 180 degrees, stay a while and then settle in at about 195 degrees. During normal driving, it will stay at 195, but eventually will creep to 210 degrees. It will stay there and then back off some to maybe 200 degrees. I can't tell you why it does this. No hills. No excessive speed. I've never seen it go above 210 degrees no matter what I was doing. This includes driving, idling and stuck in a little traffic. I'm not completely happy with the 210 degrees but I don't know if it's necessarily a bad thing. What are your thoughts on this??? I've read where some engines never get hotter then 170-180, so my 210 certainly makes me think about this. Many thanks, Nicholas.
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post #2 of 24 (permalink) Old 05-19-2019, 12:49 PM
 
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Iron headed 400... sounds about right to me.
No steam or over flow pouring out right? Id say you’re good to go.The only way you’d get it down lower is with some electric fans...

2006 GTO M6

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Bunch of suspension
Bunch of brakes
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post #3 of 24 (permalink) Old 05-19-2019, 12:56 PM
 
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If I am not mistaken, you may have the temp sender in the side of the head? I don't know what year they began doing this, but if you do, the placement in the head will read higher than the intake crossover on the earlier years.

I always suggest purchasing one of the hand held laser temp guns from the local auto parts store and shoot a couple places to see what temp readings you get. Gauges/sending units are not always accurate. The laser temp gun will give you piece of mind.
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post #4 of 24 (permalink) Old 05-19-2019, 08:42 PM Thread Starter
 
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Iron headed 400... sounds about right to me.
No steam or over flow pouring out right? Id say you’re good to go.The only way you’d get it down lower is with some electric fans...
No. Nothing coming out. No puking at all. A while ago it was doing that and I would keep refilling it. A vicious cycle I was in until I learned that it would puke out what it didn't need, seeking it's own level in the radiator. I went for a ride yesterday and it was probably about 78 degrees out. Forty five minute ride. Acted as I described. Put it in the garage and checked it this morning. Not a drop on the floor.

Jim, the sending unit is in the intake manifold. It's an Autometer electric gauge. I always liked the mechanical gauges but couldn't figure out how to get the sending unit through the firewall. I do have an infrared laser temp gun and will give that a try. For sake of argument, if my temperature gauge is reading 200 degrees, and I shoot the area where the temperature sending unit is, shouldn't this also be 200 degrees?? Thanks, Nicholas.
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post #5 of 24 (permalink) Old 05-19-2019, 10:00 PM
 
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No. Nothing coming out. No puking at all. A while ago it was doing that and I would keep refilling it. A vicious cycle I was in until I learned that it would puke out what it didn't need, seeking it's own level in the radiator. I went for a ride yesterday and it was probably about 78 degrees out. Forty five minute ride. Acted as I described. Put it in the garage and checked it this morning. Not a drop on the floor.

Jim, the sending unit is in the intake manifold. It's an Autometer electric gauge. I always liked the mechanical gauges but couldn't figure out how to get the sending unit through the firewall. I do have an infrared laser temp gun and will give that a try. For sake of argument, if my temperature gauge is reading 200 degrees, and I shoot the area where the temperature sending unit is, shouldn't this also be 200 degrees?? Thanks, Nicholas.


Yes, your gauge should reflect what you see on the laser. If not, then the gauge/sender would be suspect.

Shoot a couple other areas while at it - upper & lower radiator hose, a few spots on the radiator and even the exhaust manifolds to see that they run about the same as each other - which will not be the same as the H2O temps.

My '73 Fury temp gauge is way off (checked with the laser gun) and the oil pressure showing on the factory gauge on my brother's '48 International is 10 lbs low as checked by a mechanical gauge. Electrical gauges can be less than accurate.
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post #6 of 24 (permalink) Old 05-20-2019, 08:04 AM Thread Starter
 
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OK. Thanks. I will check it and report back, Nicholas.
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post #7 of 24 (permalink) Old 05-20-2019, 09:52 AM
 
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I have a customer with a pontiac 400 in a 77TA. He’s got 2 temp gauges. The analog temp gauge reads about 10degree’s hotter than the temp gauge on the holley sniper. Both sending units are installed on the cross over on the front of the intake. Not exactly sure why but things like that do happen.

2006 GTO M6

Motor - Stock with Vararam
Bunch of suspension
Bunch of brakes
Stock tune

365/368 std
12.81 @ 110.6 2.03 60'
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post #8 of 24 (permalink) Old 05-20-2019, 01:40 PM
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GTO44 is correct. I recommend Lectric Limited sending units for their accuracy. About your engine temps, they are basically normal. You have a heavy car with a 3.55 gear and an automatic. All contribute to a little higher operating temperature. The temps in my '67 GTO went down quite a bit when I removed the 3.36 rear gear and installed a 2.56 gear. Low rpms= less heat generated. 210 degrees won't hurt a thing unless it induces the engine to ping. Start to worry if temps are in the 230 and up range.
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post #9 of 24 (permalink) Old 05-20-2019, 01:50 PM
 
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Well said by all, you are OK Nick as long as you are not pinging or overheating. With a 3.55 gear you get higher RPM’s and that causes heat, more power also more heat,....an overdrive would drop that temp some. Also make sure that your fan is half in and half out of the shroud and it only pulls through the shroud,....but I think you are OK.
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post #10 of 24 (permalink) Old 05-20-2019, 02:09 PM Thread Starter
 
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Well said by all, you are OK Nick as long as you are not pinging or overheating. With a 3.55 gear you get higher RPM’s and that causes heat, more power also more heat,....an overdrive would drop that temp some. Also make sure that your fan is half in and half out of the shroud and it only pulls through the shroud,....but I think you are OK.
I have no pinging at all. My initial timing at idle is about 14 degrees. No hot starts. I used 93 unleaded octane and I add a bottle of Lucas Octane Booster to every tank. My fan in the shroud is correct and I can't think of anything else I could do to the motor to have it run a little cooler. I like the 3.55's alot. They give me the best of both worlds. As mentioned, my normal driving is about 45-50 mph. I tach around 2300-2400 rpm's or so at those speeds. I am going to check it with the infrared gun when I get it out next.
Thank you everyone with taking the time to respond. I do appreciate it, Nicholas.
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