Small block Water Pump

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CUDACOX

CUDACOX

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Hi All, This might sound like a Dumb Question,but.. When building a 340 with X Heads, can a 8 blade water pump be used or would it have to be a 6 blade? I have heard that an 8 blade can only be used with Aluminum Heads.Any Comments? Thanks, Craig.
 
I recently replaced my 6 blade with an auto parts store 8 blade... works just fine on my 340 with x-heads. Pay close attention to the housing shape if you have air, some of the auto part store options have a large "hump" cast into them that may cause issues with the a/c compressor...
 
8 blade water pump on my small block.....6 blades were for non A/C cars...8 blades were for heavy duty or A/C cars

IMG00022-20101020-2256.jpg
 
I found some info on the web that said 6 blade was for a/c cars (said the info came from '69 factory service manual), and I took off a six blade from my a/c car. I am not 100% sure if this is true ... anyway my 8 blade works great, and I will send the 6 blade out to be rebuilt when I get the a/c working...
 
View attachment 340right.jpg

I have a .040 over 340 with J heads that have 2.02/1.60 valves with a Be Cool radiator.

I put an AC water pump on it and have heating issue. Also had a large underdrive water pump pulley which has been changed.

This is what i found out,

FACTORY AC CARS HAD 6 BLADE with smaller water pump pulley to speed air flow thru the radiator and Non AC had 8 blade & larger pulley so the water flow thru the engine is the same on an AC car as on a NON AC

I'm going to switch to a 8 blade high flow pump, even though I have AC on my car, also have electric fan so no need to worry about fan speed.
 
if the lager shaft 'w/reinforcement tubes' 6 blade pump was with a/c in mind, it's due to the extra belt causing more tension and further out on the shaft.

I have a 6 blade in the shop that has the tubes and larger shaft, check the shaft diameter on that 8 blade, bremetric.
 
What came off my Aspen was an 8 blade..it is non A/C car and has a larger pulley so that's what I put back on it because of no over heating issue..the radiator is smaller than a 22" small one and it does fine in hot *** Texas..there have been several tests that state the stock 8 blade one flows the best gpm at low and higher rpm....
 
1wild&crazyguy said:
if the lager shaft 'w/reinforcement tubes' 6 blade pump was with a/c in mind, it's due to the extra belt causing more tension and further out on the shaft.
Click to expand...

1wild&crazyguy,

"... further out on the shaft" suggests that different water pumps might stick out farther from the timing cover. Is that what you mean? I just put the newer style aluminum water pump (72+?) on my '65 273. It looks just like the photos (didn't count the blades). Problem is it sticks out ~1" more than the stock cast-iron pump, which prevents me from installing a clutch fan. I will also need to get a later style pulley (deeper) to locate it in the correct plane.

I went with the later style because I could only buy the later style 22" radiators (lower tube on pass. side), so needed the corresponding pump. Also, the aluminum one is lighter, cheaper, and looks better. I didn't imagine a different size.
 
same shaft length between the 6/8 blade 'new style'
I know cause I switched with no issues.

Iyou need the deeper wp pulley and maybe even the newer crank pulley and alt brackets to move it outward some.

or...have your cast iron re man'd with an 8 blade impeller.

I'm not super wise on the early pulley configuration and what it would all take to switch to the newer pumps, I do know that the early A power steering cars had the pump bracket mounted to the driver side wp housing.
 
An 8 blade pump will cavitate earlier than a 6 blade at higher rpm's, not a good choice for 4:11's and small tires.
 
Got my Aspen R/T started back up today...it has two row small radiator and the eight blade water pump and a high flow thermostat and it ran at 160 degrees at 87 degree ambient air temp...
 
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