3/4" NPT
Water pump heater hose fitting
Melting Slicks
Joined: May 2002
Posts: 2,717
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Plugged mine today. removed the bypass hose on my BBC and plugged.
1/2" NPT both stewart stage 4 pump and intake were the same, all parts on my car are aftermarket.
Neal
1/2" NPT both stewart stage 4 pump and intake were the same, all parts on my car are aftermarket.
Neal
Race Director
Joined: Jul 2004
Posts: 12,706
Likes: 329
From: Scottsdale Arizona
Isn't that odd. I know that the hose sizes are 3/4 inch and 5/8 inches. Both the fittings on my water pump (also Stewart) are the same and though they don't have any markings are 0.81 inches OD at the top of the threads. Can't be 1/2 inch but it doesn't seem likely that trw and 77 are just guessing. Odd 
Melting Slicks
Joined: May 2002
Posts: 2,717
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Isn't that odd. I know that the hose sizes are 3/4 inch and 5/8 inches. Both the fittings on my water pump (also Stewart) are the same and though they don't have any markings are 0.81 inches OD at the top of the threads. Can't be 1/2 inch but it doesn't seem likely that trw and 77 are just guessing. Odd
3/4" NPT drill size is 59/64" (.9219)
OD of 1/2" NPT pipe thread are .84
OD of 3/4" NPT pipe thread are 1.050
Neal
Last edited by chevymans 77; Aug 21, 2007 at 03:53 AM.
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Thread Starter
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Joined: Mar 2007
Posts: 91
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From: London, UK
I was confused about the whole thing too. I have a SBC 1979 and am replacing the water pump with a GM Performance aluminum pump.
I measured the outside diameter of my existing hose fitting and found it to be just over 3/4 inch. When I searched for one to order with my pump I found that almost all were 1/2 NPT and only found one 3/4 NPT?
From all your responses I am thinking that the correct one to buy is a 1/2 NPT with 3/4 barb for the heater hose? I'm lost......
Also the top plug (that some use for water bypass) has a 1 inch diameter and I have only found 2 available. I guess I am not understanding the correct way to measure these fittings
I measured the outside diameter of my existing hose fitting and found it to be just over 3/4 inch. When I searched for one to order with my pump I found that almost all were 1/2 NPT and only found one 3/4 NPT?
From all your responses I am thinking that the correct one to buy is a 1/2 NPT with 3/4 barb for the heater hose? I'm lost......
Also the top plug (that some use for water bypass) has a 1 inch diameter and I have only found 2 available. I guess I am not understanding the correct way to measure these fittings
Race Director
Joined: Jul 2004
Posts: 12,706
Likes: 329
From: Scottsdale Arizona
Race Director
Joined: Jul 2004
Posts: 12,706
Likes: 329
From: Scottsdale Arizona
Basd on Neal's post, looks like it's 1/2 inch NPT. It would explain why all the fittings that you find are 1/2 NPT. I've noted this before when looking for pipe nipples for my water pump.
