[dhcarguy]

I flushed the cooling system and I bought a new 4 core Harrison look a like radiator from our host. The temperature still climbs to almost 230 degrees when I run on the highway above 3000 rpm.(3.90 rear,4 sp.). I have the stock water pump also.
What can I try next?

Thanks, Dave

[grandville455]

Where is your jetting? timing ?

[1967Tempest]

Originally Posted by grandville455

Where is your jetting? timing ?

Fan set-up?
Pump clearance?
Top gear ratio?
Compression ratio?
Fuel octane? Straight gas or ethanol?
Crank pulley and water pump pulley diameters?
Rear tire size?
Ambient temperature?
T-Stat temperature?
Spring in lower rad hose?
Top rad hose smooth or ribbed?
Water Wetter?
Rad cap pressure?
Over flow catch can?
Auto trans cooler in radiator?
Headers or manifolds? (adds to under hood temps)
Is your E-Brake adjusted?

[Pontirag]

x2 on that entire list . I think with your rear end gears that may be causing your problem. 390's at sustained highway speeds will tax any cooling system. 230 plus degrees is kinda high so I would look at some other areas mentioned above

[GT182]

Dave, go to a lower rear ratio. You don't race do you, so why need 3.90s? 3000 rpms with 390 gears out on the highway will make it heat in a big way.

[steve25]

The gears are not the cause of the over heating for gods sake, Hell Pontiac sold cars with 4.33 gears that could cruse at highway speeds all day long!
What is your total timing at, and do you have at least 10 degrees of vacume advance on tap?
At highway speeds the only things that will make for overheating are 1) timing, 2)Jetting, 3)restricted water flow, or 4) a fan set up that moves tons of air at idle but blocks the needed air flow when traveling down the road.

[Pontirag]

steve, your wrong and your right, 390' and up gears will cause overheating and especially on the highway. dont know what your thinking there but even the literature written back in the day comented, not complained, but commented that engine temps creaped up 'There" at highway speeds. so with that gearing it was a common problem.back then. hence all the extra cooling capacity that went olong with special order gear sets. and racing packages.

390 and up gear sets were for quarter mile drag racing ,maybe 11-18 seconds at a time. Not driving from Kansas to Nevada at 90 MPH or 16 hour road trips.Those kinds of cars were trailered or operated at much more sensible engine speed on high way or road trips.

but your right that other contributory factors should be looked at. You cant put a set of 433 gears ina car and not look at other demands it plces on the car.

[Formulabruce]

Originally Posted by Pontirag

steve, your wrong and your right, 390' and up gears will cause overheating and especially on the highway. dont know what your thinking there but even the literature written back in the day comented, not complained, but commented that engine temps creaped up 'There" at highway speeds. so with that gearing it was a common problem.back then. hence all the extra cooling capacity that went olong with special order gear sets. and racing packages.

390 and up gear sets were for quarter mile drag racing ,maybe 11-18 seconds at a time. Not driving from Kansas to Nevada at 90 MPH or 16 hour road trips.Those kinds of cars were trailered or operated at much more sensible engine speed on high way or road trips.

but your right that other contributory factors should be looked at. You cant put a set of 433 gears ina car and not look at other demands it plces on the car.

I agree, and will add that there is NO lead in gas ( cooled valves, and took heat out of engine) AND there is at least 10% Alcohol, which makes the engine WORK harder to do the same job it used to do with less rpm.
pump plate clearance, Fuel ratio, timing, and T stat should be at 160 for sure in this application.
maybe even run one heat rating colder spark plug

[Pontirag]

I was always under the impression that alcohol in fuel reduced combustion amd engine temps.

[steve25]

I had a 68 firebird for a while with 4.33 gears and a 4 sp behind a worked over high comp(10.7 to 1 iron heads) 400 cid, and on the highway at 60 mph it never topped 200 degree`s with a 3 row radiator.

[Pontirag]

yea, actualy when I think of sustained hiway speeds with a 433 rear i'm thinkin about 60 mph's. but out here anything less than 80 mph stays to the right...by law.

so actualy your right.

[dhcarguy]

Originally Posted by 1967Tempest

Fan set-up?
Pump clearance?
Top gear ratio?
Compression ratio?
Fuel octane? Straight gas or ethanol?
Crank pulley and water pump pulley diameters?
Rear tire size?
Ambient temperature?
T-Stat temperature?
Spring in lower rad hose?
Top rad hose smooth or ribbed?
Water Wetter?
Rad cap pressure?
Over flow catch can?
Auto trans cooler in radiator?
Headers or manifolds? (adds to under hood temps)
Is your E-Brake adjusted?

Compression ratio : (guess from previous owner = 10.75)
Cam : lunati, 230 dur., 460 lift ,
For fuel : I run 5 gals of 93 Sunoco mixed with 1 gal of leaded Sunoco 112 octane.
Timing : 11 degrees idle , 34 degrees all in.
T-stat : 180
Jetting : 68 in center, 70,s in ends
Plugs : AC Delco 45s
Manifolds : Stock
Hoses : smooth w/ spring in bottom hose.
Cap ; 15lb
Pullys : stock
Rear : 3.90

How would I be able to tell if the fan is restricting air at highway speeds??
Would running cooler plugs, like 44s, help ??
Would a 160 t-stat help??

Thanks everyone.......I still learning

[grandville455]

Originally Posted by dhcarguy

Compression ratio : (guess from previous owner = 10.75)
Cam : lunati, 230 dur., 460 lift ,
For fuel : I run 5 gals of 93 Sunoco mixed with 1 gal of leaded Sunoco 112 octane.
Timing : 11 degrees idle , 34 degrees all in.
T-stat : 180
Jetting : 68 in center, 70,s in ends
Plugs : AC Delco 45s
Manifolds : Stock
Hoses : smooth w/ spring in bottom hose.
Cap ; 15lb
Pullys : stock
Rear : 3.90

How would I be able to tell if the fan is restricting air at highway speeds??
Would running cooler plugs, like 44s, help ??
Would a 160 t-stat help??

Thanks everyone.......I still learning

Are you running vac advance?

[Franko67]

Originally Posted by dhcarguy

Compression ratio : (guess from previous owner = 10.75)
Cam : lunati, 230 dur., 460 lift ,
For fuel : I run 5 gals of 93 Sunoco mixed with 1 gal of leaded Sunoco 112 octane.
Timing : 11 degrees idle , 34 degrees all in.
T-stat : 180
Jetting : 68 in center, 70,s in ends
Plugs : AC Delco 45s
Manifolds : Stock
Hoses : smooth w/ spring in bottom hose.
Cap ; 15lb
Pullys : stock
Rear : 3.90

How would I be able to tell if the fan is restricting air at highway speeds??
Would running cooler plugs, like 44s, help ??
Would a 160 t-stat help??

Thanks everyone.......I still learning

Have almost identical problem to what you are having with a '67 GTO. Its a Tri-Power with stock '66 jetting. '70 400 Ram Air III block .030 over, 96 heads. Lazer cams hydraulic roller, dont have the cam card in front of me but it is over .500 lift. Hooker comp. headers, timing is at 17 intial and 37 total. Running a mix of 93 unleaded and VP Q16 race fuel. Rear is 3.55. 160 thermostat. 20 lb cap. Running the March performance serpentine set up, had the Edelbrock aluminum water pump that came with the kit. Took it apart last week to check the clearance from the pump to plate and it was just under a 1/4 inch. Pump was also starting to leak from weep hole. Replaced pump with stock rebuilt pump with stamped impeller. Clearanced plate to impeller to .055 of an inch. Car still went to over 220 on highway. Ordered new Flow Kooler pump from PY, should have it next week and will try that one. Havent checked the lower hose to see if it collapses, will check that next as well. Changed the advance curve yesterday, timing wasnt coming all in until close to 4000 rpm, changed it to come in closer to 2200. Car drives a whole lot better, more responsive, more power around town. Just have mechanical advance only, wondering if putting on a vacuum advance would help it some too?

[goatracer]

Stock mechanical fan or electric? Shroud or no shroud?

Bryan

[GT182]

Originally Posted by dhcarguy

Would running cooler plugs, like 44s, help ??
Would a 160 t-stat help??

Cooler plugs? Possible but not sure. Could possibly cause detonation too with highter octane fuel. Don't know for sure.... just an idea to think about.

160 t-stat? Not really. Remember, they came with 190 or 195s from the factory. I say 180 is the lowest to use so moisture doesn't accumulate in the engine.

There's a guy here I was talking to last week that said he's not running a thermostat. He's using a restrictor instead and his temps stay at 180 with it. I've no idea what size it is. All he said was to experiment with the hole size to get the temp you want. Must be some kind of waher with a certain hole size in it for coolant flow. Sounds good but I'm very leary of going that route.

What is your mix of antifreeze to water Dave? I've been told that in the hotter areas like ours and down south to run 30% to 70% water with Water Wetter added. It's helped my temps come down, along with everything else I've done.

[1967Tempest]

How are the temps at idle? Does it sit right at t-stat or just above? Might need that A/C kit with the flaps to cover the area around the rad. Air might be going AROUND the rad instead of through it.

[geeteeohguy]

Drive it at 2500 rpm down the highway and see if it overheats. At over 3000 rpm, you are generating a lot more heat that has to be gotten rid of...simple physics. The stiff gear may not be the entire problem, but it's a big contributor, IMO. Put a 3.23 in it and enjoy the good gas mileage, better traction, and reduced engine wear...(as well as being able to cruise at 70mph!)

[GT182]

Highway speeds back in the 60s were still at 50/55 and maybe 60 tops on the Interstates that were around. So sure 4.33 gears wouldn't be much of a problem back then. But for today, any speed seems to be fair game locally and out on the Interstates. 70 to 80mph with 4.33s is gonna make the engine run a lot hotter than it would back in the 60s, especially with the crap we have now for gas.

[Formulabruce]

Originally Posted by Pontirag

I was always under the impression that alcohol in fuel reduced combustion amd engine temps.

Alcohol has MORE calories than the Gasoline its mixed in. ( Calories are a measure of how much heat something produces when its burned)
10% alcohol runs, burns hotter but is way less dense than regular gasoline.
It makes cars run even leaner.
Also,Since your car is working harder to reach the same goal, you get more heat..
The epa ratings with e85 will tell you this on window stickers on brand new cars and trucks.