C2 water pump 3839175, need some details

[Alan Drake]

Sorry, back on the water pump issue for a Mar64 FI car. Need some conformation on the 3839175

Are the original pumps date coded?? Believe they are not and only the later units in the 70's are date coded.

Is the rear plate flat steel secured with pan head screws?

The Bypass is a 1/2NPT fitting with the later units 3/4NPT, therefore any pumps available with the 3/4NPT are not correct for a 64 car.

Have found a number of 175 pumps however a mix of the above items varies and I want to get the correct one the first time. If a later pump is available and one grinds off the date code on a pump that has the 1/2NPT and replaces the rear cover with a solid flat cover secured with pan head screws - Is the result an original look alike pump??

Thanks for your ideas.
Alan

[Jack H.]

Re: C2 water pump 3839175, need some details

Dating on Saginaw castings is thought to have started sometime in 1965. I've got one '175 pump that's dated in the May '65 timeframe.

On 'massaging' a core to make it 'correct' for your needs, this is a game of 'appearance'. Yes, there ARE guys out there who 'grind' off casting dates and, using something like a punch, repetitively 'tap' on the cast iron surface to simulate the as-cast surface texture.

Also, there are adaptor sleeves that can reduce a 3/4-inch NPT bypass outlet to 1/2-inch. And, there are guys who'll install a reducer, mill it flush with the upper boss and re-texture that area of the pump to mask/hide the reducer's installation.

Bottom line, while this/that modification may pass judging scrutiny, YOU are the hardest judge you'll ever meet. You know what's right/wrong on your car and it boils down to a matter of personal pride. If you can live with 'cooked' parts on your car, hey, have at it! Some can't bring themselves to this and insist on taking the time/paying the price for real McCoy items. So, it's a personal ethics issue...

[John D.]

Re: C2 water pump 3839175, need some details

Alan, A friend of mine said this past year that he has seen a lot of water pumps with a date code on them but not on the outside of the casting. The inside of it. Never verified this though. This is just trivia but interesting stuff. Course no one will ever see the date except you will know and it might bug you. It's like guys wanting the correct dates for the bottom of FI intakes. Makes them feel better and some day when the car changes hands it will look more like the "real deal". John

[Alan Drake]

Re: C2 water pump 3839175 - 1/2 v 3/4 NPT

Can I assume that if a pump has the 3/4NPT it will also be dated?

Assume that the correct 175 pump for my car is NO date, 1/2NPT, and what about the rear plate and its screws?

Seen some 175 pumps with raised back plate and hex bolts - no date code.
Then then some same as above but with the 3/4 NPT
Assume none of these are correct, but modified??

[Robert Jorjorian]

Rear plate is attached with hex bolts *NM*

[Jack H.]

NO! Assume nothing...

Like Joe Lucia said in an earlier post, the casting number ONLY differentiates the housing of the water pump. Any secondary operations performed on that casting (like drilling and tapping the upper boss for external bypass) were a part of the process that took a generic casting to a finished GM PN (the PN is NOT on the part).

So, if a given casting was undrilled (internal bypass), or drilled/tapped for 1/2-inch NPT (Corvette and other HP passenger car applications) or drilled/tapped all the way out to 3/4-inch NPT (most truck applications), the raw casting number on the water pump housing tells you NOTHING. Plus, some after-market rebuilders made a 'one fits all' part.

They'd drill the upper boss to 3/4-inch and throw a blind pipe plug in the box (fits & works with internal bypass engine configurations) as well as a 3/4 to 1/2 inch reducing sleeve (install it an you've got a HP Corvette/Camaro water pump). That saved them after-market part inventory proliferation...

[John D.]

Re: Rear plate is attached with hex bolts

Robert, When I saw the pics of the 326 I said to myself the slotted screws were used on the earlier pumps. My Feb built 63 engine has the 609 with the hex bolts. But I have another early 609 that has the slotted screws. Don't know if the early 609 is dated. When did the 609 for from slotted screws to hex bolts. Also what are the correct head logos Robert for the late 609's. Do you always go by Robert??? Jr.

[Robert Jorjorian]

Slots I think end in 1960 pumps,YES always Robert *NM*

[John D.]

Re: Slots I think end in 1960 pumps,YES always Rob

Robert, Could you elaborate your answer please. Like putting it in the message box which is much larger than the subject. All this NM's lately from the guys. You learn a lot from NM's.
So slotted screws end in 1960 pumps. What years were the 609 pump used for the Corvettes. Remember we had about a 100 posts on this pump. Drove me crazy and cost lots of bucks trying to get the correct pump on my 63 FI car. First had a 326 and the guys said car much to early for a 326. Then bought a 609 that was rebuild. Then had it re-rebuilt because you know what happens when you assume someting. So now the car has a a 609 with hex bolts. Had a nice thick backing plate from a 1980 Corvette pump and said boy that one's like brand new. But it was too thick. In all the posts didn't see one guy mention anything about the distant between the hub and the flange where the pump mounts. Course that wasn't the issue. Had to use a reinforcement spacer so the pulley's would line up on my 609. Wish I could answer a question though with NM. Jr.

[Robert Jorjorian]

Re: Slots I think end in 1960 pumps,YES always Rob

JR I believe slots end on 1960 SBC water pump back plates, when the plate changed from solid to stamped tin.
My favorite hex on a 609 is R

[John D.]

Re: Slots I think end in 1960 pumps,YES always Rob

Robert, Althought he judges at the big shows aren't looking at the pump numbers sometimes you can easily spot a 609 vs a 326. Someone pointed this out to me this past year. SO I lined up the two style pumps and the 609 is all on it's own. With only 45 minutes a car permitted at the big shows cause toooo many to judge the pumps seem to be overlooked. As long as they have the correct configuration, fittings, and hardware they fly. The 63 manual though doesn't say anything about a 609 pump does it??? I think the manual lists 326's and 175's but I haven't looked at it for a while. So what other logos do you see besides R on the hex Robert M. Jr.

[Robert Jorjorian]

63-64 JG is comedy of errors......find R bolts JD *NM*