1972 small block 3991399 to 330813 water pump changeover

[Patrick H.]

Do any of you with April / May / June / July 1972 Corvette small blocks (L-48 or LT-1) know if your car still has the original water pump? If so, would you mind checking the pump casting number? Date on the pump would be interesting if you can read it, but casting number is the primary part of data I'd like to know. I've already narrowed down the casting date changeover to about April 1st, 1972.

I'm trying to "pin down" the changeover from the 3991399 pump to the 330813 pump. The 330813 pump used in late 72 does not have the large boss on the top tapped and plugged. It has a smaller, non-tapped boss. So, if you have a pump with the large tapped boss (see upper picture below) then it's not correct and I don't need to know anything about it. The water pump in the bottom picture below is a 3991399 on an early 72.

The Judging Guide lists both 20 000 and 22 000 as possible serial number changeover points depending which paragraph you read. I'd like to see if it's a range, and if so then correct the next edition of the JG.

Thanks,

Patrick

[Henry A.]

Re: 1972 small block 3991399 to 330813 water pump changeover

The bottom pic looks like it is of my 72....am I correct?

[Patrick H.]

Re: 1972 small block 3991399 to 330813 water pump changeover

The bottom pic looks like it is of my 72....am I correct?

Yup.
I knew the pics was in my collection and easy to pull up.

[Harmon C.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Patrick
I would be interested in the data but mostly the use of the plug in the first picture. As a 73 judge I'm looking for a pipe plug with a square head and would like to know if the one in your picture could be correct for an early 73 built car built in Sept. 72 or if it was ever correct for any Corvette.

[Don L.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Patrick
I would be interested in the data but mostly the use of the plug in the first picture. As a 73 judge I'm looking for a pipe plug with a square head and would like to know if the one in your picture could be correct for an early 73 built car built in Sept. 72 or if it was ever correct for any Corvette.

Lyle, by "square plug", do you mean the one in the attached pic? I recently removed this pump and replaced it with the correct 399 casting.

[Patrick H.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Lyle, by "square plug", do you mean the one in the attached pic? I recently removed this pump and replaced it with the correct 399 casting.

Don,

Casting number and date on your former pump?

I'll admit that I have no idea what the casting # and date are on my 72 as shown in the first pic. Maybe I should check.

Patrick

[Edward J.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Patrick, My Apr Late 72 Corvette Has The Water Pump Without The Boss The Date On Pump If Im Reading Correctly Looks To Be C22, The Part No Must Be Under The Pulley I Cannot Seem To See It Even With The Mirror On The Bottom.(ser. No Is 519388)

[Don L.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Don,

Casting number and date on your former pump?

Patrick

Dunno, but will climb up in the attic and retreive/check/advise later this afternoon.

I'm rained in today, and plan to tinker on the car. Hmmm. One thing I'll do is re-tape my vacuum harness - know what I mean?

[Patrick H.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Patrick, My Apr Late 72 Corvette Has The Water Pump Without The Boss The Date On Pump If Im Reading Correctly Looks To Be C22, The Part No Must Be Under The Pulley I Cannot Seem To See It Even With The Mirror On The Bottom.(ser. No Is 519388)

Ed,

I'd pay to to check that casting number.

However, my bet is that it will be a 3991399 based on the casting date. I own a C 8 2 that is a 3991399.
If you can check at some point I'd be grateful.

[Patrick H.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Dunno, but will climb up in the attic and retreive/check/advise later this afternoon.

I'm rained in today, and plan to tinker on the car. Hmmm. One thing I'll do is re-tape my vacuum harness - know what I mean?

LOL!

No rain here "yet" though it looks like it could hit at any moment.

[Edward J.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Pat, Ill Check Later Today And Let You Know.

[Don L.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Me too thinks the C22 is a 3991399. Mine is a C 23 1.

When researching the numbers for my project, Bill Mock advised me that these pumps were made in batches, and for my August 11, 1971 built engine, the closest he'd ever seen was the March 1971 batch. It fit my date window (barely), so I took it.

Patrick/Lyle, my "former pump" as shown in my earlier pic is GM 330813. How 'bout that? Looks like the date is H 25 2. What is this?

[Edward J.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Pat. Casting Date Is C82 And Part No. Is 3991399. I Got A Better Look W/ The Pulleys Out Of The Way.

[Patrick H.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Me too thinks the C22 is a 3991399. Mine is a C23.

When researching the numbers for my project, Bill Mock adivsed me that these pumps were made in batches, and for my August 11, 1971 built engine, the closest he'd ever seen was the March 1971 batch. It fit my date window (barely), so I took it.

Patrick/Lyle, my "former pump" as shown in my earlier pic is GM 330813. How 'bout that? Looks like the date is H 25 2. What is this?

Don,

C 2 3 doesn't make sense. Mar 2 1973?!? Not if they stopped making them 1 year earlier... Maybe a C 23 1?

Most parts are batch built. FYI my June 71 (71 MY car) had an August of 70 (!) 3991399 on it.

I would suggest that your other pump is for an early 1973 motor. It may have some value to a 1973 owner.

[Don L.]

Re: 1972 small block 3991399 to 330813 water pump changeover

Don,

C 2 3 doesn't make sense. Mar 2 1973?!? Not if they stopped making them 1 year earlier... Maybe a C 23 1?

I "typoed". Typing too fast causes errors, eh? See edit - I fixed it to read C 23 1. Indeed that's what it is.

I would suggest that your other pump is for an early 1973 motor. It may have some value to a 1973 owner.

I plan to take it to Carlisle, hoping someone can use it. First need to know that it's not just a "general" pump...

Now. Back to the vacuum taping...