Wrong SB Waterpump?

[Tom W.]

I have a 1971 350/270 with AC & PS.
I've noticed that my waterpump pulley has a wobble to it.
Pully P/N is 3991434BY which I believe is correct for this engine.
There were 4 washers being used as spacers between the pulley and the waterpump mounting flange. When I removed the washers and placed the pulley back onto the waterpump, the pulley rubs against (what I believe is a bypass fitting snout - see attached photo). There is no P/N on the waterpump. "H14" is in raised letterson the right side of the pump. Also, "60" and "19" are stamped under the shaft. It has a weep hole above & below the shaft.

The archieves mention that "pump #3991399 was used only for 1971-E1972 Corvette small blocks and some MD/HD trucks of that period. Overall, it's one of the rarest of all Corvette waterpump castings.
It was the ONLY waterpump casting of short leg, large bearing, reinforced snout and no upper bypass fitting. So, as you say, it's very easy to ID without even looking at the casting number."

So, my questions are:
1) Is this the wrong pump for this engine? I believe the answer will be Yes.
2) Any recommendations on where to find the correct pump?
3) Any recommendations on how to space the pulley so I can drive with this pump?

Thanks in advance.
Tom

[Patrick H.]

Re: Wrong SB Waterpump?

Yes, it's the wrong pump. Any generic GM replacement will likely be fine.

However, I had a similar problem on my 71. The hub was too close to the pump and the pulley rubbed. I was able to use a puller (steering wheel type?) and move the hub forward on the shaft. It didn't take much movement to correct the problem. I then epoxied the hub in place once I verified that the pulley was now no longer hitting the pump and would run freely. Over 20,000 miles later, no issues.

Patrick

[Michael W.]

Re: Wrong SB Waterpump?

Your pump looks like a '73 and up small block config which will function perfectly. As Patrick H stated, probably the only issue is that the pulley mounting flange is located too far rearward on the shaft.

[Joe L.]

Re: Wrong SB Waterpump?

I have a 1971 350/270 with AC & PS.
I've noticed that my waterpump pulley has a wobble to it.
Pully P/N is 3991434BY which I believe is correct for this engine.
There were 4 washers being used as spacers between the pulley and the waterpump mounting flange. When I removed the washers and placed the pulley back onto the waterpump, the pulley rubs against (what I believe is a bypass fitting snout - see attached photo). There is no P/N on the waterpump. "H14" is in raised letterson the right side of the pump. Also, "60" and "19" are stamped under the shaft. It has a weep hole above & below the shaft.

The archieves mention that "pump #3991399 was used only for 1971-E1972 Corvette small blocks and some MD/HD trucks of that period. Overall, it's one of the rarest of all Corvette waterpump castings.
It was the ONLY waterpump casting of short leg, large bearing, reinforced snout and no upper bypass fitting. So, as you say, it's very easy to ID without even looking at the casting number."

So, my questions are:
1) Is this the wrong pump for this engine? I believe the answer will be Yes.
2) Any recommendations on where to find the correct pump?
3) Any recommendations on how to space the pulley so I can drive with this pump?

Thanks in advance.
Tom

Tom-----


The pump is a GM #330813 or, if without casting numbers, a clone thereof. This pump was originally used for L1972-82 Corvettes and is SERVICE for 71-E72.

The fit between the pulley and the waterpump casting for these pumps is "hit-and-miss"; yours "missed". The same thing can happen with a GM #3991399 which would be correct for your car. You can do as Patrick mentions and move the flange out by just a small amount. You can also relieve the casting in the areas where the contact occurs using a die grinder. Usually, very little material needs to be removed.

However, in your case, if the pullies were aligned with the washers previously used as spacers, then your best bet is to move the waterpump flange forward. If there was some misalignment when the washers were used, then your best bet is to grind the reliefs.

[Tom W.]

Re: Wrong SB Waterpump?

Patrick/Joe:
Thanks for the info. I'll try moving the flange forward a bit. Looks like I have plenty of room on the shaft. I'm guessing that you applied epoxy around the front & rear of the flange to ensure the puller didn't permanently loosen the whole setup. Would the 2 part JB-Weld work OK?

So, if I keep the current pump in place, what do you estimate the judges would say? Does this unit look much different than the original? I've not seen an original yet. I don't believe they can check Part numbers anyway.

Thanks again for your sage advice.
Tom

[Joe L.]

Re: Wrong SB Waterpump?

Patrick/Joe:
Thanks for the info. I'll try moving the flange forward a bit. Looks like I have plenty of room on the shaft. I'm guessing that you applied epoxy around the front & rear of the flange to ensure the puller didn't permanently loosen the whole setup. Would the 2 part JB-Weld work OK?

So, if I keep the current pump in place, what do you estimate the judges would say? Does this unit look much different than the original? I've not seen an original yet. I don't believe they can check Part numbers anyway.

Thanks again for your sage advice.
Tom

Tom------


The GM #3991399 differs from the one you have in a VERY obvious way----it has no bypass fitting or boss on the top of the pump, at all. Believe me, no one will need to look at a casting number to tell the difference. However, the pump you have is 100% functional for your application.

[Patrick H.]

Re: Wrong SB Waterpump?

Tom------


The GM #3991399 differs from the one you have in a VERY obvious way----it has no bypass fitting or boss on the top of the pump, at all. Believe me, no one will need to look at a casting number to tell the difference. However, the pump you have is 100% functional for your application.

Exactly. Once you see a real one, you'll understand.

Be careful putting anything on the front surface of the hub. Remember - the pulley has to mount there.

Patrick

[Jeff W.]

Re: Wrong SB Waterpump?

Tom, here is a picture of the WP on my 72. Hope this helps you.
Jeff

[Patrick H.]

Re: Wrong SB Waterpump?

Tom, here is a picture of the WP on my 72. Hope this helps you.
Jeff

Jeff,

The 71 pump is different from your 72. It has only a very small bump on top, not the larger boss/bump seen on yours.

Patrick

[Joe L.]

Re: Wrong SB Waterpump?

Jeff,

The 71 pump is different from your 72. It has only a very small bump on top, not the larger boss/bump seen on yours.

Patrick

Patrick-----


Yes, the pump pictured is a GM #330813 casting although it's an early one that is not drilled and tapped for the bypass fitting.

[Patrick H.]

Re: Wrong SB Waterpump?

Patrick-----


Yes, the pump pictured is a GM #330813 casting although it's an early one that is not drilled and tapped for the bypass fitting.

Yup.
I'm looking for one for my 72. They're not easy to find.

Patrick

[Joe L.]

Re: Wrong SB Waterpump?

Yup.
I'm looking for one for my 72. They're not easy to find.

Patrick

Patrick-----


Yes, they are difficult to find since they were only used for a short time in 1972. However, I'll bet a drilled and tapped example could be "converted" in a non-discernable way without too much trouble.

[Gerard Q.]

Re: Wrong SB Waterpump?

A pic of my wp...71 s/b

[Joe L.]

Re: Wrong SB Waterpump?

A pic of my wp...71 s/b

Gerard-----


Yes, that's the correct configuration for a GM casting # 3991399 water pump

[Tom W.]

Re: Wrong SB Waterpump?

Yes, it's the wrong pump. Any generic GM replacement will likely be fine.

However, I had a similar problem on my 71. The hub was too close to the pump and the pulley rubbed. I was able to use a puller (steering wheel type?) and move the hub forward on the shaft. It didn't take much movement to correct the problem. I then epoxied the hub in place once I verified that the pulley was now no longer hitting the pump and would run freely. Over 20,000 miles later, no issues.

Patrick

Patrick:
Yesterday, I successfuly "pulled" my WP flange forward using a 3-prong puller (Alot of WD-40 helped). The pulley now clears the WP just fine & everything is purring like a kitten. Thanks again for your advice.
I never would have assumed that I could fix the problem in that fashion. The forum is a great resource !
Tom