# Yet ANOTHER engine temp. question....



## Flambeau (Dec 30, 2013)

Okay, I promise Ive already searched and read all the engine temp posts but I still have questions and need y'alls help. 

I have a nearly 100% stock '68 GTO with 67k miles and factory A/C. The only upgrades have been a new Edelbrock carb and a mechanical temperature gauge - that's it. 

I haven't had this car long and it was in nearly a storage state for the last 25+ years. The owner maybe did 50 - 100 miles a year just to keep it running. So a couple weeks ago I went on a little highway trip and used the A/C and about 50 miles into our trip (doing 70ish) I got a temp light and a bunch of coolant boiled out. I let it cool off, refilled the coolant and turned the A/C off and didnt get the light again on that trip. When I got home I had the A/C checked and the R12 was 2 cans low. I had the A/C services and I installed the temp. gauge.

Now Ive driven her another 150 miles since then and when Im driving around town, the car stays around 225 and when I get on the highway, she wants to be just shy of 230, like 228-229. When I turn the A/C on, she stays around 230 at any speed. I double checked the temp gauge with a laser temp gun pointed at the brass fitting that is in the block and its accurate. 

So, is this normal? Seems hot to me but before I got the gauge I was driving around fat, dumb, and happy because the light doesn't come on until 240. 

Any input would be appreciated, thanks...


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## SCG Pontiac (Feb 23, 2014)

Has the water pump been replaced my guess would be at some point it has. The cast impeller pumps are getting replaced with the MUCH less efficient stamped steel. You have probably already read about the indexing trick on the pump divider. When is the last time you checked your timing. Timing can make a big difference in operating temps. The factory set the red light at 243 degrees on your car that is what they considered too hot. When you installed your gauge you probably watch it more than the road now. If you still had only a light you would have no concern at 228 because you wouldn't know it was at 228. Bottom line it would be nice to see 200 under all driving conditions but that is not reality. 210 to 220 is not hot. 230 to 240 is hot. Many people wonder how our cars can run hotter today than 45 years ago, you only need to look at the gas we put in them today for the answer. Lead made a huge difference in friction and friction = heat. Put a piece of tape over the gauge and enjoy your GTO .


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## geeteeohguy (Feb 2, 2008)

Pretty much what SCG said. 230 plus is too hot. The fact that it runs hot all the time tells me it is likely a water pump/flow issue. You need a pump with a cast impeller and it needs to be clearanced to the divider plate. It's not a fan issue, or it would run cooler on the freeway. Is your radiator core in good condition: has it been rodded out? Where is the timing...is the vacuum advance hooked to manifold vacuum? How is the carb jetting: is it too lean? I am aware that you have the universal, multi-valve relief pistons in your engine. These pistons have a rounded edge, sit low in the hole, and are known to run hotter than regular flat top pistons due to poor quench. That could be part of the issue, but would not cause the overheating you are experiencing in and of themselves.


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## rexs73gto (Nov 25, 2012)

Flambeau, I run a water pump with the stamped steal impeller, but I had to spend a lot of time to clearance the divider plate so it was within 20ths. & that took care of my problem as I to had a problem with my car running a bit hot. If I didn't stay driving the car it would over heat in about 2 min's of sitting still. I took off the pump clearanced the divider plate close & put in a 180 T-stst. I to made sure the timing was set right on , which it was but I did take it down 2 degrees just to be safe. I added some of the BE Cool stuff that helps bring the temp down. Now I can idle all day long if needed & it doesn't get over 190 degrees. I have a 462 with E-heads & the car runs 11.50's. Clearance the divider plate as close to 20 ths as you can & like with mine I do believe thats what fixed mine.


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