Inline 6 water pump question.

[CJ Loeffelholz]

Good evening, fellas.


I noticed my 1970 C10 with an I6 engine was making some racket, and I identified the water pump bearing as the culprit.

I ran to NAPA to grab a replacement pump, picked it up and it looked correct. I painted it, pulled off the old one and then noticed the offset is different.

The one I pulled off has a 3-7/8 offset from the mounting surface to the mounting surface of the fan pulley - and add to that an 1/8 spacer that was stuffed in there too. The NAPA one only has a 3-1/4" offset.

In the interim, I yanked the water pump and fan off of my 65' and installed them, which out to get me by until I can identify what pump I need.

The engine is stamped F0318TCK. Can anyone give me any advice as to what pump I should be using? Is this the correct engine for a 1970? I figured it was the original 250, but maybe it's not. Or maybe I got the wrong part from NAPA.

[silverstreak]

TCK is listed in my GM parts catalog that I saved from the dumpster many years ago.
1970 250 cid 155hp
C-10,20,30 K 10,20,30 P20,30
4 speed and HD clutch


Might be boxed wrong. They might have an illustration catalog with various specs.

[CJ Loeffelholz]

Originally Posted by silverstreak

TCK is listed in my GM parts catalog that I saved from the dumpster many years ago.
1970 250 cid 155hp
C-10,20,30 K 10,20,30 P20,30
4 speed and HD clutch


Might be boxed wrong. They might have an illustration catalog with various specs.

You rock. I can't tell you how much I appreciate the help. I've been sitting here since I posted this hoping someone would reply. My truck has a long spacer or standoff between the pulley and fan to place the fan closer to the radiator. I'm sure that's supposed to be there. It has to be the wrong part in the box from NAPA - it's the only thing that I can figure.

I looked up the part myself on their website, and the part number appears to be correct. I wish I had another truck nearby to compare that dimension.

[silverstreak]

Another possibility is when they rebuilt / assembled it, they might have pressed the pulley mounting flange on the shaft too far.?????

[CJ Loeffelholz]

Originally Posted by silverstreak

Another possibility is when they rebuilt / assembled it, they might have pressed the pulley mounting flange on the shaft too far.?????

I thought about that too, but that would be 5/8" too far. I don't think there's that much extra shaft to pilot into the pulley.

[Shyguy]

I worked at two different box auto parts stores for quite a few years and it is not unusual to find the wrong part in a box. There are quite a few ways it can happen.

When I bought a water pump for the 250 I have in my '67 out of a '70 Chevy car the first one I got was the wrong one. They had to order it since they did not have it in stock so I took the first one back and had them re-order another one, when I got the second one it fit perfect.

[68gmsee]

My original water pump on my stock 68 six cylinder, which I still have, also measure 3 7/8. I bought a replacement from Auto Zone some years back and had no problem with fit.

You probably just have to keep returning it until they get it right or go to another distributor. Napa's not what it used to be and does not always have the proper fit or best parts. Sign of the times these days...

[CJ Loeffelholz]

Originally Posted by 68gmsee

My original water pump on my stock 68 six cylinder, which I still have, also measure 3 7/8. I bought a replacement from Auto Zone some years back and had no problem with fit.

You probably just have to keep returning it until they get it right or go to another distributor. Napa's not what it used to be and does not always have the proper fit or best parts. Sign of the times these days...

You're absolutely right. I drove to the NAPA (30 miles each way) again this morning and very apologetically asked them to look at the other pumps with the same part number to compare. They pulled a different one, and lo and behold, it was correct. They exchanged it without question, which was nice, considering I soaked the whole thing in lacquer thinner to get the paint off. I can't imagine that the the seals any good.

[Shyguy]

Thank you for letting us know you got the right water pump.

I am about in the same situation distance wise as you to the nearest auto parts place.