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Discussion Starter #1
What is the normal operating temperature on the original 1972 temperature gauge when driving at +-80mph, and what is it if driving at 110mph. Is it normal for it to get higher at a higher speed?
 

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Well, I bought an Auto Meter guage to replace my original temp guage because I wanted to know numbers. Mine sat at about 1/4 of the sweep (With a new sending unit) and when I got my Auto Meter it said about 165deg. So at about a 1/4 of the sweep on the stock guage, mine is 165deg. Not sure how different it is for the 71-3, or the 351C, but this is a 69 351W guage. And, I am runing a 160-165 thermostat.
 

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I've done no sustained driving at that kind of speed. My 351W ran cooler at higher speeds up to 80 MPH than lower speeds. This was before fan shroud was installed. It now runs cool at all speeds. I don't even get to middle of gague.
 

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it can be normal under load but on average it should only raise by degrees. Most often at higher speed the temp will decreese and will increase at the lower speeds due to less air traveling over the fins. best thing to due though is get a real temp gauge and get the numbers since those old gauges are just that old. springs loose tension and can be inacurate.
 

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If your engine is really getting that much hotter going from 80 to 110, you might want to be sure you're not detonating by putting it under that much load. Use some octane boost or other additive (or retard your timing a bit) and try to go that speed. If your temperature decreases, you know you're detonating which can be DEVASTATING to your engine; the best thing that can come out of that is a blown head gasket, and it gets worse from there.
Do you have headers? My gauge was always towards the bottom half unless I was sitting in traffic, but since I've put headers in, I'm much closer to midrange (underhood temp is WAY higher now) and it gets HOT when I'm just sitting in traffic.
 

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Discussion Starter #6 (Edited)
Thanks guys. A couple of other things I should have asked, but was to tired to really think straight. As you may have guessed this is the first time we have taken her on a long run, went normally for the first 50 odd miles, but she was definitely begging to go faster:). She gets up to about 110 no problem, barely touching the accelerator, goes up hills like a dream as well, but regarding the water temp, the fan shroud is broken, obviously by someone trying to get to the pulleys or something down that way, could this cause the high temp? Our Sierra's whole shroud and underbody stuff is geared towards cooling the engine [V6] and if we removed anything for whatever reason we would notice the temp going up. Also the timing - she has a slight metallic sound when she idles, like an old VW engine, also makes a metallic pinging noise when we pull off, just on the pull off.
Tyres, do they affect the temp. at all, if they are wider surely it puts more stress on the engine [woman logic here]. And I mentioned in an earlier post that the intake manifold was 'sweating' out fuel on the one side, actually forgot about it till now, we bought another gasket set for it, but she was in the body shop for so long that it just slipped my mind. Here's a pic of the radiator shroud and the 'sweating'. Also seems to be running a bit rich, could get aphixiated if I stood behind her for long.
No Headers.
 

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If you have an intake leak, your engine will run hotter because of a lean fuel condition. I would pull your spark plugs and "read"them. If they're very white, (especially on one bank or a few cylinders) you could have a leak. Also, you can sometimes spot detonation by plug condition. If they're all pretty much the same, it could also be jetted to lean. Intake leak and lean carb not a good thing. Overadvanced timing could play a role too. Tired radiator, loose water pump belt, etc. Good luck! Bob
 

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Discussion Starter #8
"Good luck! Bob"

Thanks, I think. Hmm and we were going to work on the ranchero this week, guess it will be the cougar instead. First off going to change the IM gasket and torgue it down properly, then check the plugs, once I source some new ones, kinda scarce for good quality ones, then gotta find a good carb. guy, thats going to be a mission, replace or rebuild the radiator shroud,..........................and so on. Yep, I need that luck, thanks Bob.
 

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Ok what the other guys said is a possiability but, 9 out of 10 times these old cars that run cool at low speeds and tend to run hotter or overheat at highway speeds or above is because of lack of cooling capacity. Meaning your radiator could be partialy plugged and restriciting capacity and flow.

That little bit of fan shroud missing has no bearing at freeway speeds as the air passing over the raidator virtually renders the fan itself almost useless. Dose the car cool back down quickly when speeds are reduced? If not thats another sign of a bad radiator.


It is possiable if the radiator is up to snuff that you should check for a lean condition at higher speeds.mm
 

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Discussion Starter #10
She takes quite awhile to cool back down to just under the middle of the sweep. Radiator looks good, no busted fins or anything, will have it checked out tho'. Problem is our fear of letting any of these ham handed guys here do anything to anything. They stuff up something and we are going to s**t to find a replacement.
Another thought, the car is originally from upcountry, we are at sea level, could it be that the jets have been set for high altitude and running her here is causing a problem, once again, to find a good holley mech. There is a lot of spillage on the carb, now I'm old fashioned, I believe that if the carb is designed to keep fuel in, then thats what it should do, I don't go for this 'its only sweating' crap that I hear all the time. Fuel, oil, water, they got their place, and they got no business spilling/leaking out anywhere.
 
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