Topic: Water Pump for a 1971 Big Block
in Forum: C3 Cooling and Heating Systems
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Here we go again. Sorry, I know there are plenty of posts on that same subject but I couldn't find definite answers to my questions.
Those big block are know to be hard to keep cool. I have been struggling with the cooling system when I was in Florida and I am struggling again. If I have to change the water pump:
1) Can you confirm that only "short" water pumps would fit in my 1971 LS5, as opposed to "long" style. I found a few posts on this topic, but there was a change in 1971 and I couldn't find a CLEAR answer.
What about the shaft?
2) Of course, I am considering going with a "Hi-flow" water pump. Stewart offers "stage I" and "stage II". According to the description, the only difference is cast iron vs aluminum. Weird denomination, then...
What is the benefit of the aluminum beside the weight? Any drawback? Any corrosion side-effect?
Thank you for your comments and suggestions.
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
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#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Take a look at the pump that is on the engine now. It's fairly easy to see the difference between the long style and the shorty.The long pumps have extra cast on "fins" on them that are easily visible. The short pumps are pretty much smooth. You can also do a little measuring to see which one you have now.
I personally see no need for any fancy type pumps. Hi flow is ok, but you would also need a hi flow thermostat to take advantage of the pump's flow capacity. Another issue with a hi flow pump is pushing the coolant thru the radiator too quickly. If the coolant runs thru too quick, it doesn't have time to actually COOL....it has to be in contact with the cooler outside air going thru the rad to do any good. The best bet is to use a design the same as OE used. You have to treat/repair the entire cooling system to get the best results. This includes making sure ALL of the seals for the rad and shroud are in place, and in good condition. If this is an A/C car, be sure the condenser isn't packed full of road debris(bugs, ciggy butts, cats, etc.), as well as the radiator. Make sure you have a good front air dam. The big block cars used an air dam that was deeper(longer) than the small block cars, so be sure yours has the correct dam.
Lots of heat, and a small engine compartment on these cars can make cooling them tough....but it can be done.
dam spel chek...
|UPDATED|9/9/2015 10:15:47 AM (AZT)|/UPDATED|
I personally see no need for any fancy type pumps. Hi flow is ok, but you would also need a hi flow thermostat to take advantage of the pump's flow capacity. Another issue with a hi flow pump is pushing the coolant thru the radiator too quickly. If the coolant runs thru too quick, it doesn't have time to actually COOL....it has to be in contact with the cooler outside air going thru the rad to do any good. The best bet is to use a design the same as OE used. You have to treat/repair the entire cooling system to get the best results. This includes making sure ALL of the seals for the rad and shroud are in place, and in good condition. If this is an A/C car, be sure the condenser isn't packed full of road debris(bugs, ciggy butts, cats, etc.), as well as the radiator. Make sure you have a good front air dam. The big block cars used an air dam that was deeper(longer) than the small block cars, so be sure yours has the correct dam.
Lots of heat, and a small engine compartment on these cars can make cooling them tough....but it can be done.
dam spel chek...
|UPDATED|9/9/2015 10:15:47 AM (AZT)|/UPDATED|
Joel Adams
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Christian - browsing around the interwebs the other day and I came across a GM Technical Bulletin that reminding me of your post. It dealt with '70 - '73 BB cars with A/C and over heating problems.
|UPDATED|9/11/2015 12:04:13 PM (AZT)|/UPDATED|
The TB is number 73-T-28, I believe it highlights the larger air dam Joel mentions plus the switch from the standard clutch fan to a fixed flex blade fan. Hopefully newer radiator technology keeps you from going this route, but I thought you might be interested in reviewing it.
Do a search for a website called the "The73Spot" and click on Technical Bulletin's from the home page. You may also find it other places on the web by searching for the TB number. PM me if you have any difficulty finding it, I can e-mail you a copy.
Good Luck and let us know how everything turns out. !!
|UPDATED|9/11/2015 12:04:13 PM (AZT)|/UPDATED|
John Sigmund
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
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#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
There is another page(install instructions) to this TSB....somewhere....however..it was put out for the later, soft-nose cars. The premise is the same, tho....ya needs more air thru the rad. 
Joel Adams
C3VR Lifetime Member #56
My Link
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
OK. Here is the explanation for all my concerns:
Thermostat, Pump and Fan are doing fine. I was just not getting the expected flow rate because the rad was clogged. Has been re-cored 2,000 miles ago or so.
Now, the system is completely flushed down to the cylinder side-walls, and I am mounting the pump back (Stewart, Hi-flow). I have ordered a Dewitt Direct-fit (1239069M) and waiting for it.
I am fairly confident my overheating issues will soon become history.
Thanks y'all for your tips and advices.
Thermostat, Pump and Fan are doing fine. I was just not getting the expected flow rate because the rad was clogged. Has been re-cored 2,000 miles ago or so.
Now, the system is completely flushed down to the cylinder side-walls, and I am mounting the pump back (Stewart, Hi-flow). I have ordered a Dewitt Direct-fit (1239069M) and waiting for it.
I am fairly confident my overheating issues will soon become history.
Thanks y'all for your tips and advices.
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Crestview (near Pensacola), FL - USA
Joined: 9/16/2015
Posts: 22
Vette(s): 1970 built 454 coupe., M21, 336-1 rear, numbers matching . Approx. 550 hp/600 tq. #2 Condition . For Sale : $32,000 very firm . Have a full write up with closeup walk-around video for the serious minded only please.
Ive got a stage 3 Stewart Pump on my built BB . Cools extremely well with a Dewitts Radiator. Had I to do it all over again, I think I would have popped for the little extra money and got a stage 4 Stewart Pump with a 4 row Radiator now that I moved to hot FLorida from Illinois. But if youre in a non tropical area of the nation, you should do fine with a Stage 2 or 3 . A Stage 3 will move a bit more water Stewart told me .
1970 built 454 coupe., M21, 336-1 rear, numbers matching . Approx. 550 hp/600 tq. #2 Condition .
For Sale : $32,000 very firm .
Have a full write up with closeup walk-around video for the serious minded only please.
For Sale : $32,000 very firm .
Have a full write up with closeup walk-around video for the serious minded only please.
Former Member
Send PM
Crestview (near Pensacola), FL - USA
Joined: 9/16/2015
Posts: 22
Vette(s): 1970 built 454 coupe., M21, 336-1 rear, numbers matching . Approx. 550 hp/600 tq. #2 Condition . For Sale : $32,000 very firm . Have a full write up with closeup walk-around video for the serious minded only please.
Ive got a Stewart stage 3 pump on my BB. No problems at all. Wish i would have popped for the stage 4 though....stage 4 is a monster capacity pump., perfect for our FLorida climate
1970 built 454 coupe., M21, 336-1 rear, numbers matching . Approx. 550 hp/600 tq. #2 Condition .
For Sale : $32,000 very firm .
Have a full write up with closeup walk-around video for the serious minded only please.
For Sale : $32,000 very firm .
Have a full write up with closeup walk-around video for the serious minded only please.
in Forum: C3 Cooling and Heating Systems
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