[brianl269]

I have a 67 250HP 326 in my 65 Pontiac. Engine is stock except for Edelbrock Performer cam. My heat problem is opposite of most. I can drive around town, or idle ALL DAY and never go over 195 degrees(w/180 thermostat). When I hit the highway it slowly creeps up to 220-230. If I exit and start driving street again or even just pull off and let it idle, temps drop back down to mid 190's within 5 minutes. Never overheats on street, only at highway speed. I observed flow with cap off and it moves well when t-stat opens, no boiling over or spillage. I'm running 50/50 although I'm in So. Cal and don't need any freeze. I have a flex fan and factory shroud in place. I've used Wetter in my other Pontiac but never in this one. Since the problem is specific to highway, I don't think chemicals are the issue, but if I knew the answer I wouldn't be asking you guys.
Any help appreciated! Ya'll haven't let me down yet!

Brian
writebrian@charter.net

[brianl269]

I have a 67 250HP 326 in my 65 Pontiac. Engine is stock except for Edelbrock Performer cam. My heat problem is opposite of most. I can drive around town, or idle ALL DAY and never go over 195 degrees(w/180 thermostat). When I hit the highway it slowly creeps up to 220-230. If I exit and start driving street again or even just pull off and let it idle, temps drop back down to mid 190's within 5 minutes. Never overheats on street, only at highway speed. I observed flow with cap off and it moves well when t-stat opens, no boiling over or spillage. I'm running 50/50 although I'm in So. Cal and don't need any freeze. I have a flex fan and factory shroud in place. I've used Wetter in my other Pontiac but never in this one. Since the problem is specific to highway, I don't think chemicals are the issue, but if I knew the answer I wouldn't be asking you guys.
Any help appreciated! Ya'll haven't let me down yet!

Brian
writebrian@charter.net

[Mootie]

Well Brian my 1970 had pretty much the same symptoms--I didn't get quite that hot but same scenario-around town or idling even in 95 degree heat no worries-take it for a 75mph blast down the Interstate and the temp guage would creep down
(always liked that engineering) to the point where I would be watching it instead of enjoying the ride. Anyway-problem solved big time-it wasn't cheap and I did a bunch of stuff at once meaning not the scientific approach but heres what I did.
--Bought a kick-ass Rodney Red aluminum radiator
--Milodon aluminum water pump
--found an NOS fan shroud (mine was a bit buggered)
--new Flex-a-Lite HD Thermal fan clutch
--Complete March underdrive pulley set
--Used some Home Depot type foam pipe insulation to seal any gaps around the shroud

Like I said--turned out to be expensive and a LOT of parts--it was one of those projects that took on a life of its own after I ripped into it.

Results were great though, probably the biggest difference maker was the Rodney Red (though I can't be sure as I did all this pretty much over a weekend). Jerry makes an awesome radiator, the weld quality and finish is great-no fitment problems at all--the pulley situation evolved out of my installing the new water pump(correct for my year/engine) and as I was zipping it up I noticed my PS and Alt pulleys were out of line at least a 1/2 inch from previous. From the boards I learned that the cast iron pump on my Judge was the model that 1/2 inch shorter than it should have been--but the best part is the previous owner corrected the misalignment by coming up with his own concoction of brackets and pulleys! They were chromed, sure, I just thought they were what should have been on there. The guy I bought this car from in '94 was a big-time soybean farmer in central Illinois, and had a 40x60 work building with all kids of projects-3GTO's, 2 Chevelles, a '55 Chevy, and restored old John Deere tractors, so no telling where his rig came from!
To the point, after it was all back together, with a Stanton 160 thermostat, it was not even getting 1/3 guage sweep warm, even on the highway on those hot days--I was very surprised and pleased too. I ended up putting in a 180 (even in the summer) as I kind of like to see the guage about half mast, and thats where it stays. My Judge is a factory air car too.
I'm running the factory 7 blade RA type fan, and 50/50 antifreeze.
Hope this helps with some ideas, I will post a coupla pics if I can get my wife to "learn" me how.
Good Luck;
Mootie

[mike nixon]

what carb are you running with this combo?

what you're describing sounds like a lean condition at highway speeds.

you may benefit from a slightly richer jetting in the primary cicuit of the carb.

also check the advance in the distributor and verify the timing settings.

mike

[brianl269]

What should I be looking at in terms of timing for this car. Like I said it's nothing trick just stock with a cam. What's a good starting point?

Brian

[Ryche400]

Dont mean to jump in on your post. But I have a similar problem. I have 1980 Trans Am, with a 400 out of a 74. I am running 3.42 gears and a TH400. My problem is in town it runs about 170-180 with no thermostat. Once i cruise on the freeway above 2500 rpm, it starts to creep to about 200. Everything is new. Radiator, OE fan shroud, water pump, and a HD fan clutch. I was thinking without the thermostat, the water is probably rotating too fast and is not cooling in the radiator. Carb is a 750 Holley. The plugs do come out a bit light after a hard run also, so could be leaning out..any suggestions???

[mike nixon]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by brianl269:
What should I be looking at in terms of timing for this car. Like I said it's nothing trick just stock with a cam. What's a good starting point?

Brian<HR></BLOCKQUOTE>


you'll probably want it to have 30- 36 degrees of total timing at highway rpms. be sure the vac advance and the mechanical weights in the distributor are functioning properly.


you say the car is all stock with a cam. if this includes the carb i still think you'll need more jetting.

mike

[mike nixon]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Ryche:
Dont mean to jump in on your post. But I have a similar problem. I have 1980 Trans Am, with a 400 out of a 74. I am running 3.42 gears and a TH400. My problem is in town it runs about 170-180 with no thermostat. Once i cruise on the freeway above 2500 rpm, it starts to creep to about 200. Everything is new. Radiator, OE fan shroud, water pump, and a HD fan clutch. I was thinking without the thermostat, the water is probably rotating too fast and is not cooling in the radiator. Carb is a 750 Holley. The plugs do come out a bit light after a hard run also, so could be leaning out..any suggestions???<HR></BLOCKQUOTE>


the first ? i have for you is, are all of the spoilers on the front of this car? you need the air deflector under the front fascia to channel the airflow to the radiator.

definitly put a thermostat in to slow the flow down.

mike

[Ryche400]

Yes, all the spoilers are there. Im suppose to drive it in a parade on the 21st, so I better get my butt to work on getting the car cooled down. Nothing worse than having a car overheat during a parade.... That would suck.....lol I guess ill start by installing a thermostat and go from there.

[Brad B. Hillebrand]

Brian, quick question in addition to the others.

Is the fan a clutch or just flex? Do you have the original fan and is this an AC car. Is it the original water pump or replacement, if replacement what kind?

Couple quick tests for you that won't cost much

1) Swap out the 50/50 for straight distilled water and one bottle water wetter.

2) Install a RobertShaw extra performance balanced thermostat at 180. Most speed shops have them.

Timing is important.

Brad

"It's the last thing I'll ever say, I promise"

[Brad B. Hillebrand]

Brian, here is the link to stewart for the t-stat. I bought mine from them and were delivered in 3 days. Best t-stat on the planet (in my opinion)

Brad

"It's the last thing I'll ever say, I promise"

[Brad B. Hillebrand]

http://www.stewartcomponents.com/htm...hermostats.asp

Guess you will need this.....

"It's the last thing I'll ever say, I promise"

[STripleduce]

Flex fan could be the culprit.While increasing the rpms note where the blades flatten out, if this rpm matches your rpm at speed that overheating is caused then I would guess that the flex fan is acting like wall rather than pulling air through the rad.Clutch fans are better for street use than flex fans which are intended for track use as they flatten to reduce hp loss at higher rpms.

http://community.webshots.com/user/stripleduce

[robscar]

you may want to check to be sure that the heat riser in the exhaust mainfold is operating and opening as is should.
i once had a similar problem and this was the cause.

[Steve O]

As STripleduce said, the flex fan could be flattening out at speed...ESPECIALLY if you're using a shroud, effectively blocking out all of the air flow. Don't like flex fans...JMHO.

Steve O
1966 GTO Convertible
1968 Camaro Convertible
1995 Harley Road King
http://www.stevewaddington.com/vehicles/

[78 GHOST]

I hope you don't mind yet another opinion..

When I began reading the first post in the thread, there were a couple of things that grabbed my attention. All of the following can be checked without turning a single screw (except the flex fan.)

First, as previously mentioned the flex fan can be a problem.

Second, as Mike Nixon recommended be sure the mechanical advance is operable. They get funked up and frequently malfunction, causing problems with heat. Use a timing light and a check of advance up to 3,000 RPMs, it should all be in by then.

Third, examine the lower radiator hose while checking the mechanical advance (when you have the RPMs up) and verify it's not being collapsed by water pump suction. Older hoses had a wire inside to prevent this. Newer hoses allegedly don't need this wire because the rubber is of a better compound.. I say allegedly.

Fourth, verify you aren't suffering any vacuum leaks.

I hope I don't bore you by reinforcing the message others have initiated.. these are things that have bitten me in the past.

Best of luck, -Matt

____________________________________
Much love out to my Peeps

[Ryche400]

Well, I put a thermostat,as well as a severe duty fan clutch, and still the car runs hotter than it should. You know how embarrasing it is to be cruising in a parade, and having the car start to get hot?? One thing I remember is when I was building the engine, the timing cover was kind of corroded. I was reading that the tubes that go through the cover also have to be in VERY good shape, which mine are not. I guess ill try getting a new cover, and see what happens. BTW, i have the heater fittings on the head plugged, could that restrict water flow?? Any help would be appreciated.