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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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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...
 

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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. :thumbsup:
 

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Discussion Starter #4
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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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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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.
 

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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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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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Discussion Starter #10
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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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.
You are doing great, sounds smooth. I like the “Redline S1” it is a fuel system cleaner but the carriers are an octane booster and an upper cylinder lubricant. It has PEA which is Techron and will clean carbon off valves and pistons, super stuff.
 

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You are doing great, sounds smooth. I like the “Redline S1” it is a fuel system cleaner but the carriers are an octane booster and an upper cylinder lubricant. It has PEA which is Techron and will clean carbon off valves and pistons, super stuff.
I know the jury is out yet on the verdict whether or not these octane boosters work. Some say yes. Some no. I happen to think they do work. I buy mine by the case on Amazon. Free shipping and the cheapest way to purchase. Much better then a bottle at a time at your favorite parts store, Nicholas.
 

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I agree, octane is simply an organic chemical with a certain molecular structure. That molecule resists detonation from high compression, chemistry not voodoo....

Refiners add it to their gasoline, but it costs more money so the price goes up. Now how much each tank needs?

It would take an Einstein style guy with a slide rule mind a a fast computer To figure that out so we just rely a bit on the advertising, a bit on the company selling the octane boost and a bit on our own observations.....as it is not pinging when it is added and pings when not.

Dieseling or run on after shut down is sometimes an indicator of too low an octane fuel.

That is why I like fuel cleaners with PEA, poly ether amine, the best chemical for cleaning fuel systems carbon etc. A few products have it. Again chemistry not voodoo. But a whole lot of stuff on the shelf is snake oil.....you put it in and a big bunch of smoke comes out when you race the throttle....what does that mean?....

It means it makes smoke.......smoke don’t actually mean clean......you have to look with a bores ope or small camera....

You get much result if you don’t have PEA in it. Although some fuel cleaners use a solvent and that works on gum and crud, but not carbon.
 

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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.
Have you considered the Thermo fan clutch, viscous drive could be the problem? If it intermittently changes fan speed cooling performance will be effected
 

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Hi guys. Had my car out today and wanted to get it up to operating temperature so I could take some readings. Seems like it takes quite some time to get it to 180 degrees. I ran it a little on the hard side and eventually it went to 195 degrees. Stayed there a while then crept up to 210. Never above that. Headed home and the temperature went down to about 195-200. Took some readings with my infrared gun.

189 degrees at the sender in the intake.
149 degrees upper radiator hose.
150 degrees lower radiator hose.
140 degrees heater hose.
105 degrees top of radiator.
271 degrees at driver side exhaust manifold.
240 degrees at passenger side exhaust manifold.
172 degrees at thermostat housing.

With the engine still running, it cooled off to 165 degrees on the gauge. 160 degrees on the sending unit. Kind of strange I thought?? So, what do you think?? The temperature gauge is fairly accurate?? Thanks, Nicholas.
 

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Hi guys. Had my car out today and wanted to get it up to operating temperature so I could take some readings. Seems like it takes quite some time to get it to 180 degrees. I ran it a little on the hard side and eventually it went to 195 degrees. Stayed there a while then crept up to 210. Never above that. Headed home and the temperature went down to about 195-200. Took some readings with my infrared gun.

189 degrees at the sender in the intake.
149 degrees upper radiator hose.
150 degrees lower radiator hose.
140 degrees heater hose.
105 degrees top of radiator.
271 degrees at driver side exhaust manifold.
240 degrees at passenger side exhaust manifold.
172 degrees at thermostat housing.

With the engine still running, it cooled off to 165 degrees on the gauge. 160 degrees on the sending unit. Kind of strange I thought?? So, what do you think?? The temperature gauge is fairly accurate?? Thanks, Nicholas.

So are you satisfied with the results? Looks darn good to me. Looks like the gauge reading may be off about 10 degrees based on the sending unit in the intake.
 

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Yes Jim, I think I am. I do agree with the gauge being off about 10 degrees. I might try a mechanical one sometime soon. They have always been my preference over electrical ones which I have. Thanks, Nicholas.
 

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I see no problem at all. As for the jury being out on Octane boosters, it isn't. Not to me. I have had extensive experience with most of them and have found only two to work. Octane Supreme 130 (which is actual tetraethyl lead) and Torco. I have not used the Redline stuff. The stuff you see at the counter of the auto store in the little bottles (104, 108+, etc.) is absolutely not effective, and will instead coat your plugs with yellow or red fuzz.
 

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Those temps look pretty good Nick, seem pretty normal to me. Temp guns and gauges sometimes vary....even my temp gun and my thermal imager vary a bit. Hot days and hard running can get temps up a bit, if it gets hot when you are stuck in traffic you want to make sure your fan clutch is right. They gradually leak out the silicone fluid through the seal and sometimes fail slowly over time, I think GTO mentioned it. He is right sometimes they don’t fail all at once, but slowly and the heat creeps up.

Other little things are like fresh anti freeze and water, the 1/8 holes drilled in thermostat, I do that and it helps I believe, a fresh radiator cap. It must hold the pressure at 15 or 16 lbs, the rubber seals gradually go bad as well and less pressure water heats up faster,...same as your fuel. More pressure like in fuel injection prevents fuel boil. So the cooling system is sensitive to those little things.

But look pretty good we should all always pay attention to temps Ikeep a heat gun behind my seat, and use it even when everything is good. Try it on carb and fuel lines as well
 
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