New water pump 6 impellers whats up with that!

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Oklacarcollecto said:
From the factory A/C cars used pumps with 8 blades and non A/C used 6 blades. At least that is what my original factory Mopar parts manual shows.
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Not true. The AC cars ran 6 blade pumps from the factory and the non-AC cars ran the 8 blade pumps.

I run a FlowKooler water pump on my car. Has a plate welded on the impellers to prevent cavitation.
 
Double M said:
However, I have a Factory 1970 Dodge Challenger/Dart service manual on my desk right now, and on page 7-10, towards the bottom of the page, it says 318/340 standard pump blades 4.38" - 8, Air Conditioning 3.70" - 6.
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Above is correct.

AC cars - 6 blade.
non-AC cars - 8 blade

AC cars had a pulley ratio to spin the water pump/fan faster. Both crank and water pump pulleys were different between AC and non-AC cars.
 
I have an old rusty 8 blade '67 pump (I think) Some measurements off that OEM is blades stick out .175 off the gasket surface and the impeller clearance from the housing is a measly .025 and that was scratching my feeler gauge. Blades @ 4.180, overlap the cavity/machined lip by .675. The bearing is still tight so Ill use it again as it exits out the correct side.
 
Thanks for posting that Pishta.

.025 on the housing side is good. Hopefully it fits that close on the backside too.

.
 
OK. I should have checked the service manual. You all that said use the 6 and the manual says 6 for AC cars and 8 for non-AC. You are correct. I looked at the specifications in the 1972 and it says six also. If anyone needs the manual it is available here on the forum. I’m guessing there is some reason why the AC and non-AC have different part numbers. I’ve seen both at Oreilly and they are visually different. Thanks for the discussion. Craig

 
bohica2xo said:
.025 on the housing side is good. Hopefully it fits that close on the backside too.

.
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It's been a while since I put mine together last time and I did measure the back clearance just to see what it was. Unfortunately I didn't write it down so I don't remember for sure but I'm positive it was well more than .025"... if I remember right it was on the order of .100"... The car doesn't run hot. The only reason I'm planning on changing it this time is it keeps spitting out gaskets. I checked the timing cover for trueness and it's within .001"... Never checked the pump for trueness cause it was new but there must be something wrong with it cause it's spit out 2 gaskets.
 
Double M said:
When I posted what I posted, I was going from memory. But with your post, I thought I'd check.

I didn't post what was in a factory service manual, but what I remembered reading somewhere around 1972 or so. However, I have a Factory 1970 Dodge Challenger/Dart service manual on my desk right now, and on page 7-10, towards the bottom of the page, it says 318/340 standard pump blades 4.38" - 8, Air Conditioning 3.70" - 6.

I guess my CRS isn't as bad as I thought.

Russ.
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FYI on big blocks the 6 blade water pump is for AC cars not the other way around. Pulley is smaller, turns faster, 6 blades do reduce cavitation.
 
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