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Water Pump Info circa 2019

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304-dude View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2019 at 11:31am
Originally posted by mmaher94087 mmaher94087 wrote:


The boys a MOPAR will tell of shearing the front off the pump with high horse power motors.  They recommended removing every other vane off the water pump impeller.  If one thinks about what's happening; it makes sense.  Engine revs quickly and the impeller in the pump tries to move water quickly.. water cannot be compressed.  Something breaks.


A bit of common sense... though, it will kill city driving on a hot day.

Though, my feeling is, if your engine is to run above 6000 RPM 90% of the time... then you would be better off with underdriven crank and waterpump pulleys.

Problem is they will need to be a home brew custom setup, since nobody makes them for AMC. Though if Edlebrock has both AMC and GM patern on its water pump, and your using an ATI or early harmonic damper with Chevy pulley bolt patern, you could find under drive pulleys to work.

Also I would think having power steering shared on the same belt would add side load on the pump to the torque being generated at the RPM extremes.

NASCAR and many other motor sports will offset sideloading on the pump bearing by using a separate belt to the power steering pump. Though another benefit is making belt jump minimal with using smaller belts.

There is a lot of subtle things to ponder that when added all together can make a big difference.

71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2019 at 12:35pm
I suppose you could consider the early V8 pulley setups underdrive compared to the later 4-bolt crank pulley stuff.
1968 AMX 390 w/T5
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve_P Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2019 at 4:45pm
Modern cars all use aluminum pumps and many turn 7k+ RPM.  If the AMC aluminum pumps are failing the problem isn't RPMs and aluminum, it's the design of the pump
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2019 at 4:55pm
Originally posted by Steve_P Steve_P wrote:

Modern cars all use aluminum pumps and many turn 7k+ RPM.  If the AMC aluminum pumps are failing the problem isn't RPMs and aluminum, it's the design of the pump


I dont think anyone said it was the use of aluminum that is faulty. Looking at the overall dimensions, nothing indecates the castings were enlarged enough at the snout end to retain the bearing from being pulled and breaking through. The lack of proper reinforcement on GMB castings, is never going to be as strong as iron. You would need to double the thickness at around the parameter to help with the lack of material from 90° cut for bearing and seal retension.

Haven't taken any of these aluminum pumps apart to verify how well chamfered, and thickness at the bearing seat, but assume they did not make it a critical part of manufacturing design.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ChillyB Quote  Post ReplyReply Direct Link To This Post Posted: May/14/2019 at 7:04pm
Agree with all of that.  Replicating iron parts with aluminum castings skips any design effort and goes ahead with a lot of assumptions.  Titanium gun parts are my favorite example of this.  A well designed steel part is made out of titanium instead and advertized as an upgrade.  For dimensionally equal parts steel is stronger than Ti.  Ti advantage is only realized when size of part is increased such that for a comparable weight the larger Ti part is stronger, often with addition of extensive gussetting.  A Ti scope mount dimensionally equal to steel is weaker but much lighter.  Sometimes that is strong enough.  Sometimes not.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2019 at 3:13am
GMB new iron pumps routinely only last me about 30,000 miles before the shaft bearing gets loose and begins to wobble. It gets looser until I replace it. Six and V8.

...which is why I buy them from NAPA with a lifetime warranty and keep the receipt.

No, I am not over-tightening my belts.

I wonder if the shaft seal slowly leaks and contaminates the lubricant in the bearing. I've started using an anti-rust and water pump seal lubricant additive in my coolant so we'll see if that helps.

Edited by FSJunkie - May/15/2019 at 3:16am
'66 Marlin: 327/T10/3.54 Twin Grip
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'84 Eagle: 258/TF998/2.35
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2019 at 1:10pm
I've been running GMB aluminum pumps at high rpm for years no failures. in circle track and drag. Hundreds of laps
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Hurst390 Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2019 at 1:16pm
Another basic aluminum GMB pump at work that I've ran for years with zero issues..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2019 at 6:17pm
My NAPA cast iron lifetime warranty pump started leaking after 5000 miles. Fat lot of good the warranty does me when they don't offer an early style pump anymore.
1968 AMX 390 w/T5
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2019 at 6:35pm
I wonder what accessories where on the engine that constantly broke the pump nose?

Seems like the two replies with users of the GMB pump, have tested race only motors that may not have power steering or may have a belt setup that does not overly effect torque at the nose of the pump.

Since my theory with bearing break out is based on how torque is applied through the belt setup with a base copy of tye iron core using cast aluminum.

71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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