326 water pump question

[Jack P.]

I have a 326 1968 water pump with a GM 5

I have a 326 with a GM 1

What do the numbers 1 or 5 indicate

Both have the larger bypass hole.

Jack

PS 66 L-79 motor

[Duke W.]

Re: 326 water pump question

Those are the tooling set numbers.

Duke

[Jack P.]

Re: 326 water pump question

Hi and thanks, but does that mean one was made before another......5 was the 5th tool ? Casting ?

Jack

[Joe L.]

Re: 326 water pump question

Hi and thanks, but does that mean one was made before another......5 was the 5th tool ? Casting ?

Jack

Jack------

"1" would have been the first pattern fabricated for the pump casting. "5" would have been the fifth. However, they both could have been done at essentially the same time and, whether they were or not, they could have been in use at the same time. Not too much can be inferred from pattern numbers.

[Duke W.]

Re: 326 water pump question

Most GM iron castings have these tooling set numbers embedded in the casting. At any point in production, several sets could be in use. If it was a high volume part that was in production for some time the tooling set numbers go into double digits.

Tooling wears with use. Sometimes it can be refurbished, but sometimes it's just scrapped and replaced.

If there were casting problems - either high reject rates or problems in the field like leaking due to porosity, the tooling set numbers allowed GM to trace the problem. That's why the casting part number, tooling set number, and casting dates are embedded in the castings. It's a way to track and trace quality issues.

Duke

[John D.]

Re: 326 water pump question

I have two 326's including an older one with a cast "S" in it. I have heard it's a Saginaw casting which were not used on Corvettes...is that correct ?

[Jack P.]

Re: 326 water pump question

Hi and thanks for the info, Great, I now have a # 1 casting for a 3/4 bypass, that is better than # 5 however, it is not a 1/2 " that would be correct for my incorrect car.

Jack

[Joe L.]

Re: 326 water pump question

I have two 326's including an older one with a cast "S" in it. I have heard it's a Saginaw casting which were not used on Corvettes...is that correct ?

John------


Saginaw castings were used for virtually all small block components used on Corvettes. However, Saginaw castings only rarely are identified with an "S" casting mark.

[Joe L.]

Re: 326 water pump question

Hi and thanks for the info, Great, I now have a # 1 casting for a 3/4 bypass, that is better than # 5 however, it is not a 1/2 " that would be correct for my incorrect car.

Jack

Jack------


I don't think a #1 pattern number is really any better than a #5. The '326' casting is the same regardless of whether it's external bypass boss is tapped for 1/2" NPT or 3/4" NPT.