[General Z]

Thanks, that is on my list. However, installing a new radiator from Jegs, and a water pump without a bad bearing cured my ills. Running between 170 and 180 all day, never higher than 190 any longer.

[Indiangoat]

Hello:

My 455 65 goat is overheating at idle. I think when it sits around for awhile the radiator is growing filaments of corrosion that might be causing heat exchange problems. I've already checked the:

- Ignition timing ok (9 deg BTDC)
- Plug color ok (brown)
- Jet and rod combo ok (standard for 428 Pontiac)
- Idle screws set ok (2.75 turns out)
- Fan clutch play ok (when cool the fan will spin less than one revolution when slung by hand)
- Fan shroud fit ok (only 1/4 inch gap on sides)
- Fan pulley function ok (tight),
- Fan pitch and air flow through radiator ok (piece of paper will stick to front grill when car runs hot)
- Water pump ok (new high flow aluminum water pump installed with high flow 160 deg t-stat)
- Coolant flow (not sure if its good. visual observations indicate that fluid passes by filler neck hole at about 1 to 2 inches per second. If I had a laser temp gauge I would use it to look for temp variations in radiator and block)
- Radiator hose spring to prevent hose collapse from suction is no problem (little rust on spring)
- Radiator fluid level (full but has some particulate material floating around)
- Temp gauge operation ok (Temp reading (230 deg) not confirmed but rad hoses get way too tight and engine gives off too much heat after running 15-20 minutes with outside air temp in the 90s)
- Compression test for head gasket failure ok (no turbulent bubbles or oil floating in radiator),
- No vacuum leaks on carb mounting gasket (67 carb - new metal/fiber base plate gasket)
- Only slight looseness in carburetor throttle shaft (slight air leak at shaft confirmed with carb cleaner test).

I think I need to replace my 15.5 inch 1965 Pontiac radiator. It's 11 years old and I can see some corrosion building inside which i think may have been caused by chlorinated tap water. Also, after working on the water pump and water neck over the years, I think its possible that little strands of gasket maker-sealer may have found their way inside the radiator tubes. I have decided to try a new Rodney Red aluminum radiator. Once I flush out the engine and install the new radiator, I'll dissect the old one and see what's inside.

Should I proceed?

Cruise and stay cool.

[george kujanski]

Sounds like you covered all the important stuff xcept you didn't mention if you set the impeller-to-plate clearance on the water pump.

If you did, then the radiator is the next item to change.

George

[Indiangoat]

The hi-flow aluminum water pump that I installed (Milodon) had taller impeller fins compared to the stock impeller. The bigger impeller fins looked like they significantly reduced the clearance between the impeller and divider plate hole. With respect to reducing the amount of backwash activity between the impeller and divider plate hole, and improving coolant flow, wouldn't installing a hi-flow aluminum water pump with taller impeller fins be an alternative solution to modifying the stock divider plate and changing the offset of the divider plate hole?

I wonder if on stock cast water pumps, the extra clearance distance between the impeller and divider plate was suppose to provide a margin of safety in case the water pump shaft bearings failed and the shaft began to wobble?

[george kujanski]

The taller impeller vanes certainly are a good idea, but excessive clearance between the vanes edges and the plate will make the pump less efficient.

I guess extra clearance would be a good idea in case of bearing failure, but contrary to pump efficiency, which would be good to maximize during normal operation.

so, in my opinion, i doubt if that would be the case.

george

[brohloff]

Another guy here with a hot running '67 400. Just finished reading all 47 pages of posts. After reading the first 22 pages went out and pulled the water pump. Found a cast impeller with .240" clearance. Vanes are 5/8" high (good). Installed this pump when I rebuilt the 400 at 110k miles 10 yrs ago. Also have the original removed water pump (that was working fine) which appeared exactly the same. Clearance of .220" and cast impeller 5/8" high on this one. Going to do the clearance mod and will advise temp results ........BUT have a comment and a question:

Comment: My car is a 3/67 build, 335hp/400,4spd, no AC and it has a 7 blade clutched no shrouded fan. The 67 shop manual says the no AC cars have a fixed 4 blade fan, no shroud. AC cars have the 7 blade clutched fan with shroud. I know this 7 blade clutched fan on a no AC car was an OEM setup since I ordered the car new and this is how it came from the factory. Anybody seen this on their cars? (original clutched 7 bladed fan on a no AC car).
Suspect since it was near the end of the model year build they had a lot of extra 7 bladers left so they used what they had.

Question: In all these 47 pages of posts I did not see a reference as how to check if one's fan clutch is working or needs to be replaced. This one spins with a little resistance by hand when hot or cold. But how can you be sure that once hot the clutch tightens up enough to get more fan rpms???????????????? Should they lock up solid?As long as it's now apart would like to check this part of the cooling system out.

Sorry for the long post..........Comments? bob...

[performerrpm]

i wish i woulda knew about dif impeller tolerances on my old 400 after the first pump went bad it ran hot 200 always in the summer and if stuck in traffic it really was bad, but i dont think it is the cast vs stamped pumps it is the clearance as stated because my 71 455 has the stamped pump and new divider plates and a 160 thermostat 16 inch fan with adjustable thermostatic switch and i dont think either the gauge or fan switch is right because i have it set to come on a 160 degrees but it doesnt come on til gauge reads 190 so one or the other is off but in any case the motor never leaves past 190 when the fan comes on i can let it just idle for 30 minutes if i want and when it gets movin the gauge drops t 185

[500plus]

General rule of thumb for clutch fan operation is when the engine is at normal temp and you turn off the ignition, the fan should stop spinning within 3 turns. I know this probably bring up some flack from others, but this is how most everyone I know tests them. Bill

[ginlisbon]

Well, I read all the book here and figured I would give it a shot even though my goat (74 406,Rpm intk.,87cc e-heads,4speed,4 core chev.radiator,cast pump with a stamped impeller,aftermarket plastic flex fan with a smaller 6 inch pulley vs. my stock 8")only ran 190-195 at cruise in any ambient temps and would slowly creep up to 220-230 when idleing for more than 10-15 min wich I know is caused from not having a shroud.

Pulled the pump and saw that I had about a 1/4" gap between plate and impeller.Bought a Cardone cast pump with cast impeller and the tolerence was better so I pounded it and got a gasket width.Hooked her up and now Iam running 185-188 when cruising

Still need a shroud though,still creeps at idle.Excellent info and a very simple mod that works! Thank you to all who contributed to this thread and especially to the dicoverer.

[Tony_D]

I'm new to this site and have been reading up on cooling issues. My 1966 GTO doesn't overheat per se but the TEMP light will come on (230 F?) and it will spit water after running for some time in the Phoenix 100 degree heat!
I haven't had a chance to pull my pump and check the impeller and clearance but hope I can share some data.
I have a 1966 vintage 326 engine in my garage and after reading this thread decided to remove the pump and I also took some photos. I have no idea if this is the original pump and its an 8-bolt type.
The pump front cover has "GM8" and "8772716" cast onto it.
The cast impeller has "RG" and "9773426" on it. The vanes are approx 5/8" tall and 1 1/4" measured along the length. The OD is 4 1/2" and the ID (inner circle described by the vanes) is 2 3/4 inch.
The vane clearance is approx 0.110 inch.
This engine was installed in the GTO while I had the 389 rebuilt and I did not have overheat problems and the TEMP light never came on.

There was a question earlier in the thread about the purpose of the cut out in the housing. It looks like its to avoid a cast "hump" in the timing cover. Maybe later designs did away with the cut out and just let the parts come together.

Anyway, some more input for us all to consider!

Looks like I can only attach 5 photos - I'll submit another post with the rest (3).

[Tony_D]

Here's the last 3 photos.

[Indiangoat]

I installed a new Rodney Red crossflow radiator in my 1965 GTO and installed some fan seal material (masticated rubber) between the radiator and fan shroud to improve suction. Also I isntalled an 18 inch heavy duty 7 blade fan with a heavy duty fan clutch. The motor (455 stock) runs real cool at any speed above 30 mph, but still has temperature creep when idling. It will climb to 230 deg after about 20 minutes of idling with ambient air temps in the high 70s.

I took the water pump off to reduce the divider plate clearance from about 1/8th of an inch to about the thickness of a gasket. Strange, I noticed some rust on about 1/3 of the impeller surface in my new high-flow water pump (Milodon). Even though the car sits around a lot, it seems unusual to have only part of the impeller rusting. It seems like the water pump would be full of coolant and not have any air pockets when the radiator is full. To help alieiviate potential trapped air in the top part of the pump I drilled a little 1/16th in hole in the top part of the diver plate to help let out any trapped air which could be stuck and causing cavitation. Tommorow, I'll put the water pump back on and do another idling test.

[Indiangoat]

After I reduced the divider plate clearance to about the thickeness of a gasket and made a 1/16th in hole in the top of the divider plate to let out any trapped air bubbles, the motor did not cool off as fast at highway speeds like it did before I made the change, and it seems to overheat faster at idle. Maybe flow is too great. It's flowing past the radiator filler hole at about 1 ft per second. This flow which seems fast, could be forming a thin boundry layer of slower moving water on inside surfaces of the radiator which could be acting as a buffer and hindering heat transfer from the rest of the flow. I will attempt to reduce flow by installing a standard T-stat in place of the existing hi-flow T-stat and see if that improves radiator efficiency and lowers engine temps at freeway speed.

[Indiangoat]

The 455 seems to run a little cooler at freeway speeds with a standard T-stat instead of a high flow T-stat. Maybe there is such thing as too much radiator flow after all. I think the slightly smaller orifice of the standard T-stat reduced the extra flow that I gained by installing a hi-flow water pump while simultaneously minimizing the divider plate clearance. Maybe the slightly lower flow is allowing the cooler water on interior surfaces of the radiator to mix more efficiently with the hotter water in the middle of the flow.

The motor still creeps up to 220-230 at idle though. Ugh. Since this is probably not the result of a lean condition, I think I'll try a bigger fan and fan shroud to help pull air through the new aluminum radiator. Interestingly, it's harder to see through the new aluminum radiator than a standard 4 core desert cooler when looking directly though them. The horizontal fins on the aluminum radiator that run between the vertical tubes look serrated on the aluminum radiator which allows turbulent air to move up and down within the radiator as well as go directly through from front to back. I guess this engineering design helps provide more surface area on the fins for heat exchange. Still, it's harder to see through, and it may be harder for air to pass through. Thus, I guess I'll try a larger fan (19.5 inch) and fan shroud. If that doesn't work maybe a pusher fan will help.

[george kujanski]

Either low air or coolant flow at idle will cause the temps to go up.

As a test, try increasing idle speed a bit to improve coolant flow. AIr flow will increase slightly too, but I would think coolant flow would improve more.

Did you connect vac advance to manifold vac? It will increase timing and RPM at idle, indicating more efficiency.

George

[1967Tempest]

All:
I am not sure if I posted this before and I am not looking through 30 pages to see. But since I finished, and we are now into fall, where temps are around 45 to 62 depending. I cant get the car to run warm enough to get great performance. I will say that again. TOO COLD!!! I have the Kujanski mod completed on my cast water pump. I have a overflow tank. And I have a Griffin aluminum radiator. Connected to a mild 77' 400 6X heads is a 6.25 water pump pulley and a Flex-A-Lite 18"fan (Summit part number FLX-1618P). The monster ran much cooler.between 185 and 195. But my brother knew I was having cooling issues and bought me an electric fan. Now there was no spot for it since the race fan was already installed. So we thought that it might fit between the grille and the radiator to act as a pusher. So we removed the horn support, and attached the electric 16"fan to the front of the radiator. Next I installed the Derale deluxe adjustable fan controllers with radiator probes (Summit part number DER-16759). I adjusted the fan to come on a little after the standard 160 degree thermostat opens at around 163. So once the thermostat opens the electric fan is running. Now ay 80 degree weather, I can leave the car idleing at 800-1000 rpms for hours and the temp never creeps up past 170. Now that the temp drops in the 40s and 50s. I need to adjust the electric fan to come on around 175, because when I am going down the road with the original set-up the car temp gets into the 150s.

Thought this might help. I have pictures of what the electric looks like in the front upon request.
Dave

[Indiangoat]

I modified my new plastic 1965 15 inch radiator fan shroud to accommodate a 19.5 inch fan instead of the stock 18 inch fan (see picks attached). The 19.5 inch 6 blade fan seems to pull a heck of a lot more air through the radiator (at idle) compared to a new 7 blade 18 inch fan.

The stock opening in the 1965 shroud was originally an oval (about 19.5 inches vertially and 21.5 inches horizontally), thus all I had to do was cut it in half and increase the vertical opening by 2 inches. In order to get the sizing right, I re-attached the shroud after it was cut and then riveted on the copper sheet on the inside and outside of the shroud. Also, if you do this, you will need to cut out around the bottom of the shroud to make clearance for the radiator outlet. I added reinforcement in this area too using copper sheet metal and aluminum rivets (see pics). It kind of looks Frankenstienish, but I guess I could add some fiberglass matting on top paint like others have done in this forum. Overall, the modified shroud is just as sturdy.

No more problems with temperature creep when the outside air was about 70 degrees, but I guess I'll have to wait until next summer when ambient temps are around 100 deg. to know for sure. Meanwhile, there are plenty other GTO systems to work on.

Thanks for the help George.

[Old-Goat]

Another satisfied customer, thanks George

I had two problems, someone had put just one of the old style plates in a new style housing on my 67, and i had a stamped pump. The car ran hot 210 -220 degrees. I found a cast impeller pump at NAPA (Thruflow) and got the proper plate from Ames. Adjusted the plate, ran 175-180 today on a 25 mile trip. It got to 190 when stopped for a light so I'm guessing I should replace the fan clutch as well. I'm pleased.

Oh My 67 had the 7 bladed fan no shroud as well Brholoff. I think the HO and probably the Ram Air cars had them. Mine was built Dec 66.

[fast72lemans]

I am another satisfied customer as well. I drove my 70 Lemans on my 1 hour ride to work and noticed the temp was near 210, weird since it had a 180 degree high flow t-stat and it was only 65 degrees out. I checked the coolant, level was fine?? on the drive home, it was 80 degrees and sure enough...by the time I was home, it was at 230 and just starting to push coolant. I pulled the pump off and found it was a cast impeller but had nearly a half inch of clearance. I adjusted the clearance to roughly 1/8" and re-installed. While I was there, I changed the t-stat to a 160 standard flow, and changed from a 4 blade to a 6 blade plastic flex fan(I think the stock 4 blade moved more air?) Once it was warmed up, I took some temps at the t-stat housing to compare to the gauge, The t-stat housing was 158-160, the autometer gauge was at 170-172.......weird. Took it for an extended ride, temp never moved passed 175, it was 56 degrees so the true test will be when its in the 80's but so far I'm happy. Now to replace that inaccurate temp gauge.

[george kujanski]

1/2"' of clearance?????? the pump was probably not working at all. Now it's on the cool side with a 160 stat. Once the weather gets warmer and if your temps stay around the t-stat value use a 180 stat.

George