[mountaingoat]

Im new but need info on what is probably a common question. I have a 67 GTO with the original 400 small block and I cant enjoy driving it because of the overheating. It does have a .30 overboar with 10.75/1 compression and the HO heads have been converted to run on unleaded fuel, other than that it is stock. I have tried many combinations of shrouds, fans, and thermostats but I think the real problem is in the pump itself. I did replace the impeller when i did the rebuild and have heard there are problems with the aftermarket replacement part. I shut it down when the temp reaches 210 to protect the engine but it makes it hard to get anywhere. My big problem is running in stop and go traffic, which I think indicates an air flow problem. I have tried a few shrouds, flex, clutch, and electric fans(mounted on the back too keep from restrictiong airflow), different temp or no thermostat, and even larger radiators(not yet tried an aluminum aftermarket), but none have given me a good result. I am interested on info about my water pump, dropping a gear and keeping my rpm's up helps so I think that the pump is the problem. The block was boiled out before the rebuild so im pretty sure its clear. The water pump and timing chain cover are one unit on this engine. I would really like to replace this with a more standard two piece timing chain cover and seperate water pump (a high flow electric would be prefferable), but am unable to find any info on suitable parts. If this is not an option where do I obtain one of the good cast original impellers and or a whole new unit? I will probably eventually go to a griffin radiator and electric fan setup (my desire for the electric pump and fan is to maximize the HP), am I on the right path? I have also heard of a way to increase and equalize flow through the heads by placing a nipple on the left head. Is this something i should do? if so can anyone tell me the correct procedure? One last bit, I have heard of a plate that prevents flow under the radiator and keeps air moving through the radiator, is this a part I cat buy or do i need to fabricate it myself? Any info would be greatly apreciated.

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[mountaingoat]

Im new but need info on what is probably a common question. I have a 67 GTO with the original 400 small block and I cant enjoy driving it because of the overheating. It does have a .30 overboar with 10.75/1 compression and the HO heads have been converted to run on unleaded fuel, other than that it is stock. I have tried many combinations of shrouds, fans, and thermostats but I think the real problem is in the pump itself. I did replace the impeller when i did the rebuild and have heard there are problems with the aftermarket replacement part. I shut it down when the temp reaches 210 to protect the engine but it makes it hard to get anywhere. My big problem is running in stop and go traffic, which I think indicates an air flow problem. I have tried a few shrouds, flex, clutch, and electric fans(mounted on the back too keep from restrictiong airflow), different temp or no thermostat, and even larger radiators(not yet tried an aluminum aftermarket), but none have given me a good result. I am interested on info about my water pump, dropping a gear and keeping my rpm's up helps so I think that the pump is the problem. The block was boiled out before the rebuild so im pretty sure its clear. The water pump and timing chain cover are one unit on this engine. I would really like to replace this with a more standard two piece timing chain cover and seperate water pump (a high flow electric would be prefferable), but am unable to find any info on suitable parts. If this is not an option where do I obtain one of the good cast original impellers and or a whole new unit? I will probably eventually go to a griffin radiator and electric fan setup (my desire for the electric pump and fan is to maximize the HP), am I on the right path? I have also heard of a way to increase and equalize flow through the heads by placing a nipple on the left head. Is this something i should do? if so can anyone tell me the correct procedure? One last bit, I have heard of a plate that prevents flow under the radiator and keeps air moving through the radiator, is this a part I cat buy or do i need to fabricate it myself? Any info would be greatly apreciated.

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[PHILLYGOAT]

First, you should confirm temperature with a cooking thermometor placed in the radiator. Your gauge could be way off. While the radiator cap is off check the water flow. Does it flow at low rpm,does it flow better with more rpm? Switching to a larger crank pulley/smaller pump pulley may help.
Oh yeah, drop the smallblock unless it is a Chevy.
P.S. Maximum Performance in Lakewood had an aluminum Milodon pump for $60. I can't remember which years it was for. Talk to Max ,he's a good guy.
If you go thru enough rebuilt pump boxes at the local parts store you can usually find one with a good impeller.
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Too stubborn to do it the easy way. What else would I spend all my $ and time on?

[This message has been edited by PHILLYGOAT (edited 02-18-2001).]

[mountaingoat]

Thanks for the suggestions phillygoat. I havent tested my guage with a kitchen therm but the last time the temp guage read over 220 I blew the top off the radiator. Your other suggestion to just scrap my block for something different doesnt make any sense because it is an original GTO block with matching serial #'s. I will look into the water pump though, thanks!

[PHILLYGOAT]

Mountaingoat,
What I meant is drop the term "smallblock". When referring to PONTIACS just state the size. PONTIACS are not small or big blocks, just small or big journals. OK, maybe the 301 is a small block but who cares?

[Black 65 GTO]

I would check to see your PSI rating on your radiator cap! If it is insufficient, it will raise the boiling point of your coolant!
It should be about a 14 lb cap.

Also, excessive ignition timing will cause an overheat situation. Check to see what your total timing is and make adjustments as necessary. Being that your in Denver, CO, your octane and ignition requirements could be different due to the elevation (6000 ft ?)
The elevation will also change to rating on the radiator cap, I think the higher the elevation the lower the pressure.

[Ed Neasham]

Black 65

Think you have it backwards. ("I would check to see your PSI rating on your radiator cap! If it is insufficient, it will raise the boiling point of your coolant!")Lowering the pressure - insufficient pressure rating - lowers the boiling point. By the way the boiling point at Denver is approximately 203 degrees (pressure 12.36 psia). Remember that the rated pressure of the cap is the differential between the radiator and atmosphere. So a radiator cap rated at sea level would have a boiling point of about 248 degrees, while the same system at Denver would have a boiling point of about 244 degrees.

Ed

[Half-Inch Stud]

...be sure to set your ignition timing for
Some ideas;

34degrees at 2500RPM; full-advance, vac hose disconnected.

May want to richen the fuel mixture on the carb Primaries.

If the motor does not idle well then you may want to have the distributor recurved.

[mountaingoat]

Thanks for all the info guys but i feel pretty good about my radiator cap, fuel mixture, and timing but mostly im interested in info about equalizing the flow through the heads and/or changing my pump set up. I have already tried the things suggested here and im pretty sure that the pump is my main problem. Air flow through my radiator could use some optimization but all signs point back to the pump. I am also very interested on equalizing the flow through the heads but want to make sure that i do it right so any info on this process would be greatly apreciated.

[Black 65 GTO]

Your right Ed! I should probably cut back on the Diet Coke! I meant what I said, and I said what I meant! Ha!

[llucas]

How were the HO heads converted to run on unleaded? Do you really have 10.75 to 1 compression? If you do have 10.75 to 1 compression and you are running unleaded gas, your problem is you are running the timing backed off so far that you will never cool that engine. Contrary to popular belief retarded timing will make an engine run hot much more so than advanced timing. The reason that dropping a gear makes the engine run cooler is two-fold. One, you are reducing the load on the engine, and two you ARE moving the coolant through the engine faster. Post the head casting number, the mods done to the heads, the initial and total timing, and the type of pistons you are running.

[mountaingoat]

llucas,
The heads were casting #670, they were resurfaced and hardened valves and seats complete the unleaded conversion. The pistons were from EPW (part #p587), they are cast and are flat top and were rated at 10.75/1. I have played with the timing but things seem to run best with an initial setting of 12 degrees and 29 degrees at full advance.

[Tim Corcoran]

Mountain Goat,

If everything is working properly you shouldn't have to modify anything to cool your 400 properly even in stop and go traffic at 120 degrees. The only thing I would recommend changing from the factory set up would possibly a better radiator, like a Desert Cooler or an aluminum radiator, a Bee Cool or a custom. For the street the absolute best set up is the factory parts, including the factory seven blade 17" clutch fan, AC style shroud, AC size pulleys, and factory style pump. Some of the after market pumps have inferior impellers and that could be part or all of your problem. Don't over look other possibilities such as ignation advance, vacuum or mechanical, or total advance. Too high of compression for 92 octane, or too lean of a mixture on the primaries. Like I said if everything is working properly..... You should not have to modify your factory system, all that will do is bandaid another problem. When I used to drive my 65 LeMans on the street, it was a .060 over 455 running high 11's in the 1/4, and it had all the factory cooling system stuff with the exception of a Desert Cooler radiator. It never went over 190 even in the Summer here in Phoenix at 120 in traffic. Just my .02.

Tim Corcoran

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65 LeMans 11.13@120
going into the 10's
this winter

[Reed]

Hey Mountaingoat, it may be a little late to answer, but there is a guy in the Rocky Mountain GTO club that is really up on cooling of GTO's. His name escapes me at the moment, but he has published a booklet of advice for cooling that I have seen advertised in The legend. If you drop me a line I can get you his name and number. Cooling these goats is a tough job at altitude on a warm summer day in traffic.

Reed 303.805.0071 Eves.

[71Sport]

I am not sure how far you want to go but here is my set up and it works great.
I have a 455 bore .60 over, 12.75:1 compression, block filled, running 7000 RPM. Mainly drag racing, but it goes out for the Friday night runs and to car shows in 100 + degree days.
We originally had a stock radiator with two electric fans. On hot days in traffic we would need both fans to keep it down to 200 degrees.
Okay ... now we have an elctric water pump, a griffin 1" tube aluminum radiator and twin 14" fans, and thae stock shroud. The shroud requires "minor" snipping to fit with the Griffin radiator but no big deal. Also .. we added a trans cooler and took the trans lines OUT of the radiator.
Now I have a difficult time getting the car up to operating temperature (180 degree oil temp)and most of the time I have to keep the fans off until I get to 190 - 200 degrees.

As far as the radiator goes I would check out Rodney Red. From what I have heard it is very high quality and a fraction of the price of a Griffin.