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Old 03-04-2017, 03:09 PM   #1
63frankintruck
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Water pump for L31 with Serp

Installing aftermarket reverse flow water pump with serp system
Problem------original water pump pulley for serp system has different bolt hole pattern than new aftermarket pump (see pics)

Anyone ran into this issue and have any solutions?


Sorry pics rotated, not sure how to correct this
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Old 03-04-2017, 03:50 PM   #2
B. W.
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Re: Water pump for L31 with Serp

the stock pulley has a larger center bore & bolt pattern because the fan clutch screws onto the water pump hub rather than using the four bolts to hold it on
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Last edited by B. W.; 03-05-2017 at 11:35 AM.
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Old 03-04-2017, 05:14 PM   #3
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Re: Water pump for L31 with Serp

^^^^^^^^^^^^^^^^^^^^^^

you have a standard reverse rotation pump on your l31 , the truck is the same other than the hub and fan mount..
This was done, because of passed issues of people installing the wrong rotation pump on cars .. This set up, you get the pump and go that isn't the same..

I'll bet they make a pulley for the car pump that works with that whole set..
So you don't have to replace the pump.. as long as that pump IS a reverse rotation..
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Old 03-04-2017, 08:29 PM   #4
63frankintruck
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Re: Water pump for L31 with Serp

The pump I purchased is a standard reverse rotation.
This one
https://smile.amazon.com/dp/B01L0YPH..._prd_ttl_sol_0
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Old 03-04-2017, 08:51 PM   #5
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Re: Water pump for L31 with Serp

TBI trucks ran reverse rotation also. I couldn't tell you if a TBI pulley would line up or not.
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Old 03-05-2017, 01:01 AM   #6
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Re: Water pump for L31 with Serp

The pulley you have is specific to the L30/31 Vortec water pump. What you need for your aftermarket water pump is a pulley for a '88-'95 TBI truck. I think it should line up with the other pulleys but I do not have experience with that to say for certain.
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Old 03-05-2017, 12:33 PM   #7
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Re: Water pump for L31 with Serp

call the maker of the set up.. I'll bet they will swap pulleys..
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Old 03-05-2017, 12:49 PM   #8
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Re: Water pump for L31 with Serp

From the OP's pics, it appears he is using stock L31 brackets

BW has TBI brackets on an L31 motor.
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Old 03-05-2017, 08:31 PM   #9
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Re: Water pump for L31 with Serp

Quote:
Originally Posted by Bigdav160 View Post
From the OP's pics, it appears he is using stock L31 brackets

BW has TBI brackets on an L31 motor.
Yes the brackets are from a TBI 350 motor I bought for parts (I was told that the motor was from a 97 Suburban)

Captian Fab - 85-95 TBI pulley I think is smaller diameter.

This is all I found so far-

http://www.jegs.com/i/Chevrolet-Perf...85760/10002/-1

Last edited by 63frankintruck; 03-05-2017 at 08:41 PM.
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Old 03-06-2017, 07:31 AM   #10
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Re: Water pump for L31 with Serp

Quote:
Originally Posted by 63frankintruck View Post
Yes the brackets are from a TBI 350 motor I bought for parts (I was told that the motor was from a 97 Suburban)

Captian Fab - 85-95 TBI pulley I think is smaller diameter.

This is all I found so far-

http://www.jegs.com/i/Chevrolet-Perf...85760/10002/-1
That don't matter.. other than pump speed.
you want it to have the same rib count(if aplical)/width as your other pulleys .

That part # above is for a bbc

GM Replacement Water Pump Pulley - 1987-1995 Chevy/GMC Truck 7.4L & GM Serpentine Drive Kits - Big Block Chevy


does not say gm serpentine drive kits- big and small block chevy..

I'd call and check first..

me I'd go get a pulley off a 1995-back tbi truck for 5 bucks at a junk yard..
as you need the balancer bolt and washer , the starter bolts (they are different thread /size than the 70's bolts) the dipstick tube and dipstick..
the coolant temp sender.. (threads and size is different than older engines.)

I even took the plug wire holders..

Last edited by James the III; 03-06-2017 at 07:46 AM.
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Old 03-07-2017, 12:02 AM   #11
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Re: Water pump for L31 with Serp

The serpentine water pump pulleys are not ribbed. They are smooth since the back of the belt is wrapped around the water pump pulley.

I agree with just getting a '88-'95 TBI water pump pulley. The diameter is not that critical. The other alternative is to switch to the '96-'02 L30/31 water pump.
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Old 03-07-2017, 05:50 PM   #12
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Re: Water pump for L31 with Serp

pulley diameter on 5.7 truck TBI is 5.75", vortec is the same diameter. Bolt pattern on TBI is 2.0" O.C.
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Old 10-04-2017, 08:32 PM   #13
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Re: Water pump for L31 with Serp

How did this turn out?
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Old 10-05-2017, 09:57 AM   #14
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Re: Water pump for L31 with Serp

Quote:
Originally Posted by kacy View Post
How did this turn out?
I dont know what the OP did, but I have the L31 brackets on my 350 and I used a 88-95 water pump, pulley and thermostat housing. Its working fine, I have both the L31 and the TBI pulleys and the only difference between them is the center bore and bolt pattern. The diameter is the same.

Heres what I used and the year ranges

88-95
Water pump
Pulley
thermostat housing
upper radiator hose

96-99
Bracket set
Idler
Tensioner
Crank pulley
Power steering pump and pulley
A/c delete/compressor
Belt

2003 5.3L (suburban or tahoe with 145A option)
AD244 alternator

Lower radiator hose, heater hoses and power steering lines are stock parts from my 1978 C10. I swapped the pressure line fitting from the original pump into the L31 pump to allow me to use the factory line.
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Old 10-05-2017, 12:02 PM   #15
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Re: Water pump for L31 with Serp

Quote:
Originally Posted by bluex View Post
I dont know what the OP did, but I have the L31 brackets on my 350 and I used a 88-95 water pump, pulley and thermostat housing. Its working fine, I have both the L31 and the TBI pulleys and the only difference between them is the center bore and bolt pattern. The diameter is the same.

Heres what I used and the year ranges

88-95
Water pump
Pulley
thermostat housing
upper radiator hose

96-99
Bracket set
Idler
Tensioner
Crank pulley
Power steering pump and pulley
A/c delete/compressor
Belt

2003 5.3L (suburban or tahoe with 145A option)
AD244 alternator

Lower radiator hose, heater hoses and power steering lines are stock parts from my 1978 C10. I swapped the pressure line fitting from the original pump into the L31 pump to allow me to use the factory line.

Thanks for the info I was wondering if the TBI pump/pulley would line up correctly. AS for the power steering pump, I used the pump from my 79 vette when I added serp to it. It bolted on like it was made for it.
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