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Question: 427 big block water pump pulleys

Tom66

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1966 Nassau Blue Corvette roadster
I have a 1966, 4 speed roadster with a 1975 454 block set up as a 427 with 1967 L88 heads. When I bought the car a few years ago it did not have A/C. Due to the very hot CA summers I decided to install a Vintage A/C system. The car is now running very hot, especially in slow traffic. I can hit the yellow warning line on the heat gauge, no problem. One school of thought is the water pump pulley should be smaller in diameter which will make the fan spin faster. The WP pulley is now 7-1/4". Did Corvette use small pulley's for A/C equipped cars? If so does anyone know what the diameter is and possibly the part number? If not does anyone have any idea's, other than installing an auxiliary electric fan, to make this engine run cooler. I have installed a racing high capacity water pump; not much help. It already has a 7 blade fan, but not sure if it is aggressive enough or not. It has been suggested to check the fan clutch, but I am sure that is working ok. Also to check the seals around the radiator core, work in progress. Thoughts? Thanks
 
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thinking out loud here - did you check thermostat, as maybe a "cooler" one would help, like maybe a 160; also what about the radiator what are you using currently
 

Toms007

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I was thinking that the radiators were different from non AC to AC cars....when you added the AC, did you swap radiators?
 

Tom66

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1966 Nassau Blue Corvette roadster
Water Pump Pulley

thinking out loud here - did you check thermostat, as maybe a "cooler" one would help, like maybe a 160; also what about the radiator what are you using currently

Yes thank you. I am using a 160 thermostat. I am using a "stock radiator" I have thought about replacing it with an aluminum radiator but I want to keep the car as stock as possible. Yes the engine numbers don't match but the engine looks correct.
 

Tom66

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Swap radiators

I was thinking that the radiators were different from non AC to AC cars....when you added the AC, did you swap radiators?

thanks no I didn't. I am trying to keep the car as stock as possible. I admit I may have to revisit this position if I can't get this problem resolved in other ways. I did some research and I concluded that the radiators for A/C and non A/C are the same. At least I could not find separate part numbers. Not 100% conclusive but I am relatively confident I am correct. If not please advise
 

navy2kcoupe

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Outside possibility is that the radiator is partially clogged.
Maybe take it out and have it flow tested. While it's out
would also be a good time to get any "clogs" out of the fins as well.
Spinning the pump faster might help with the temps, but it could
just be a band aid as well. Maybe one or more of the cores have
been crimped and soldered shut by a previous owner. Can't tell
what a previous owner did until you lay your own eyes on it.
Andy :w
 

Tom66

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Flow Test

Outside possibility is that the radiator is partially clogged.
Maybe take it out and have it flow tested. While it's out
would also be a good time to get any "clogs" out of the fins as well.
Spinning the pump faster might help with the temps, but it could
just be a band aid as well. Maybe one or more of the cores have
been crimped and soldered shut by a previous owner. Can't tell
what a previous owner did until you lay your own eyes on it.
Andy :w

Thanks Andy, all good thoughts; thank you. I did have the readiator flow tested and the coils are in preteen condition. I also blew them out with compressed air. They look pretty clean. You are correct I truly hope I am not creating a bandaid when something else is going on that could prove to be more serious. One interesting note is that I was told by a Corvette friend of mine that I should be able to hear the fan sucking the air, like a roaring noise. I don't so he suggested a more agressive fan and make sure the seals around the radiatior core are tight with the radiator frame so that the air is not leaking around the radiator. I have done that and it don't feel much air other than through the radiator. So I am going to try a fan with a larger CFM at low speeds to see if that makes a difference and see if I get that sucking sound from the fan. Crossed fingers.
 

navy2kcoupe

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Tom, do you think that there could be a "bubble of air"
trapped in the block? It sounds like a long shot to me,
but also might be worth checking. Sure as heck would
NOT be fun seeing all that work you put in, seizing up,
or warping the heads. Is there any such thing as a larger
volume water pump?
Andy
 

Tom66

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Air Buble

Tom, do you think that there could be a "bubble of air"
trapped in the block? It sounds like a long shot to me,
but also might be worth checking. Sure as heck would
NOT be fun seeing all that work you put in, seizing up,
or warping the heads. Is there any such thing as a larger
volume water pump?
Andy

Thanks Andy for the time and thought you have put into my question. Air bubble: been there done that. When I had the antifreeze changed last year to a "wetter" mix I got an air bubble. It turns out that big block chevy engines have a tendency to get air bubbles when changing the antifreeze; who knew? Anyway the cure is to drill a small hole in the flange of the thermostat to let air pass-by and I also ran the engine with the radiator cap off to let out any air bubbles when the thermostat pops. So I think I have that covered. I also installed with this antifreeze change an Edelbrock 8850 Victor series high flow racing water pump. Looks just like the stock pump on the outside. Helped a little, but not well enough when in traffic. Warping the heads is my biggest fears, 1967 L88 headers are not too common anymore.
 

LLC5

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Thanks Andy for the time and thought you have put into my question. Air bubble: been there done that. When I had the antifreeze changed last year to a "wetter" mix I got an air bubble. It turns out that big block chevy engines have a tendency to get air bubbles when changing the antifreeze; who knew? Anyway the cure is to drill a small hole in the flange of the thermostat to let air pass-by and I also ran the engine with the radiator cap off to let out any air bubbles when the thermostat pops. So I think I have that covered. I also installed with this antifreeze change an Edelbrock 8850 Victor series high flow racing water pump. Looks just like the stock pump on the outside. Helped a little, but not well enough when in traffic. Warping the heads is my biggest fears, 1967 L88 headers are not too common anymore.



Keep in mind that there is no cold, only absent of heat. You need to evacuate as much heat as possible from the radiator and condenser. Make sure the seal is tight around the radiator shroud and that the fan is drawing maximum amount of air past the radiator assembly. Racing water pumps can flow coolant too fast past a radiator also, not allowing proper convection. Make sure you have the proper components for a big block and a/c combination including the radiator (which will be rendered useless without proper airflow).
 
Last edited:

IH2LOSE

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1966,and a 1962 thats almost complete
Welcome to the forum. I been away for a while and stopped back in for a quick reminder of how to do things, While researching some thing for my self. I came across and excellent article written by one of the most knowledgeable men with early corvettes and Chevrolet performance I have ever had the pleasure of meeting. If you take the time to read his article you'll walk away enriched with new knowledge . What I learned from that man was its never some big giant solution , But lots of tiny minute details that never seam like much on there own but when you add them all together they are the problem

Good Luck on your journey to try and get a an air-conditioned Big Block to run cooler.

http://www.camaros.org/pdf/corv_cooling2.pdf
 
Last edited:

Tom66

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1966 Nassau Blue Corvette roadster
No cold

Keep in mind that there is no cold, only absent of heat. You need to evacuate as much heat as possible from the radiator and condenser. Make sure the seal is tight around the radiator shroud and that the fan is drawing maximum amount of air past the radiator assembly. Racing water pumps can flow coolant too fast past a radiator also, not allowing proper convection. Make sure you have the proper components for a big block and a/c combination including the radiator (which will be rendered useless without proper airflow).

Thanks again Andy, very thoughtful response and suggestions. I will recheck the cooling system as suggested.
 

Tom Bryant

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As to your question about pulleys, the 1966 non a/c and the a/c engines did use different water pump pulleys. The old parts book doesn't list diameters on these as they do one someothers which makes me think they are the same diameter with the difference being 2 groves for non a/c and 3 grooves with. The listing for a/c says "(3 pulleys)". There is a smaller diameter pulley for high performance small blocks and 427s without a/c for 1968 and 1968/1969 L88. It's part number 3848904 and it's stamped the same but it's only a 2 groove.

Tom
 

Tom66

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1966 Nassau Blue Corvette roadster
Water Pump Pulley

As to your question about pulleys, the 1966 non a/c and the a/c engines did use different water pump pulleys. The old parts book doesn't list diameters on these as they do one someothers which makes me think they are the same diameter with the difference being 2 groves for non a/c and 3 grooves with. The listing for a/c says "(3 pulleys)". There is a smaller diameter pulley for high performance small blocks and 427s without a/c for 1968 and 1968/1969 L88. It's part number 3848904 and it's stamped the same but it's only a 2 groove.

Tom

Thank you Tom, very informative. Your information makes me wonder if I am concentrating on the wrong pulley. If I might trouble you again, do you have any information on the crank pully; a/c vs. non-a/c? If they are of different sizes that may provide the higher fan speed that I think I need.

Thanks again
Tom
 

LLC5

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Thank you Tom, very informative. Your information makes me wonder if I am concentrating on the wrong pulley. If I might trouble you again, do you have any information on the crank pully; a/c vs. non-a/c? If they are of different sizes that may provide the higher fan speed that I think I need.

Thanks again
Tom


Make sure your fan clutch is working properly, at idle with the engine hot and a/c on you need to feel a real strong push of air at your hand when positioned behind the radiator shroud. If your not sure what is enough air flow, find a vehicle with a electric radiator cooling fan and do the same test with that vehicle (vehicle static, a/c on). It should be a strong force of air.
 

Tom Bryant

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I checked the parts book and other sources and I can't find diameters of these pulleys. The 1966 427 used the 2 groove cast iron pulley.

Tom
 

Tom66

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fan clutch

Make sure your fan clutch is working properly, at idle with the engine hot and a/c on you need to feel a real strong push of air at your hand when positioned behind the radiator shroud. If your not sure what is enough air flow, find a vehicle with a electric radiator cooling fan and do the same test with that vehicle (vehicle static, a/c on). It should be a strong force of air.
Thanks Tom. I don't have a fan clutch, its direct drive. However the air flow is weak. I am looking for ways to increase the air flow. Turning the fan faster is on of my thoughts. Thanks again for your time and advice.
 

Hib Halverson

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71 04 12 19
Turning the fan faster may not make as much of a difference as you think, but it will make a lot of noise and the faster you turn it, the bigger the power loss and the higher the load on the V-belts.

First of all the, a C2 BB was cooling challenged even when everything is right. Add aftermarket A/C and you're making a marginal cooling system worse. My guess is if you insist on a stock fan and a stock radiator, you're going to have to live with high coolant temperature at low speeds and when the car is stopped. Combine that with a hot day and you'd better get used to seeing the temp gauge up in the high 220s or low 230s in traffic and below 30-mph.

You said it has a "racing water pump". Not sure what that is but I'd install a modern water pump, such as an Edelbrock. Use the stock accessory drive for that engine with a new clutch fan. Make sure the proper fan shroud is installed.

Even better would be to scrap the engine driven fan assembly and shroud all together and go to an aftermarket electric fan system.

Use a 180° thermostat. Keep in mind that putting in a 160° stat doesn't necessarily lower coolant temperature. All it does is open at a lower temp. The cooling system then rises to whatever temperature it can sustain which, in your case, is obviously not 160 or even 180.

Install an aftermarket, all aluminum radiator from Griffin or DeWitts intended for use with A/C.

Also, possible issues are engine running lean at idle or low rpm, spark timing retarded at idle and low rpm, both of which will make the engine run hot.

Big Block even without air are very difficult to cool. With my 71 (modified 460-in BBC) it took a lot of cooling system mods to get the car to cool well, even at idle and low speed.
 

Tom66

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1966 Nassau Blue Corvette roadster
Pulley

I checked the parts book and other sources and I can't find diameters of these pulleys. The 1966 427 used the 2 groove cast iron pulley.

Tom

Tom, thank you for your time, very much appreciated
 

Tom66

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1966 Nassau Blue Corvette roadster
BB turning fan faster

Turning the fan faster may not make as much of a difference as you think, but it will make a lot of noise and the faster you turn it, the bigger the power loss and the higher the load on the V-belts.

First of all the, a C2 BB was cooling challenged even when everything is right. Add aftermarket A/C and you're making a marginal cooling system worse. My guess is if you insist on a stock fan and a stock radiator, you're going to have to live with high coolant temperature at low speeds and when the car is stopped. Combine that with a hot day and you'd better get used to seeing the temp gauge up in the high 220s or low 230s in traffic and below 30-mph.

You said it has a "racing water pump". Not sure what that is but I'd install a modern water pump, such as an Edelbrock. Use the stock accessory drive for that engine with a new clutch fan. Make sure the proper fan shroud is installed.

Even better would be to scrap the engine driven fan assembly and shroud all together and go to an aftermarket electric fan system.

Use a 180° thermostat. Keep in mind that putting in a 160° stat doesn't necessarily lower coolant temperature. All it does is open at a lower temp. The cooling system then rises to whatever temperature it can sustain which, in your case, is obviously not 160 or even 180.

Install an aftermarket, all aluminum radiator from Griffin or DeWitts intended for use with A/C.

Also, possible issues are engine running lean at idle or low rpm, spark timing retarded at idle and low rpm, both of which will make the engine run hot.

Big Block even without air are very difficult to cool. With my 71 (modified 460-in BBC) it took a lot of cooling system mods to get the car to cool well, even at idle and low speed.

Thanks HIb, I have been thinking along your lines as well. I did put in a Edelbrock 8850 water pump which is advertised as a high performance racing pump. Which I interpret as increased water flow, which as I find out may or may not help. So far not much help. I have been looking into aluminum direct replacement radiators which look stock. There is even have a "stock" aluminum radiator setup with electric fans as you suggested above. I think this set up will be my next step if this doesn't work out. The engine has been dyno'd at around 500bhp so loss of power is not too much of a concern, but I am a little concerned about the wear on the v belts and top and lower pulley bearings. Thanks for the validation however, at least my Plan B sounds like it is making sense. Yes I have been told by many people that BB's run hot and has been a well know problem that has been solved by going the restomod route. I may be chasing my tail since I know I am not the only one that has faced this problem and may have to make some compromises between originality and practicability. Thanks again for your time to respond to my inquiry.
 

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