71LS5

The car 1971 LS5 454 (same as it ever was)

Had 336199, GM6T, C 4 74 I believe this to be off of a 1974, it has a 3/4 in shaft-4 bolt flange.

Just got what I thought was the correct water pump 3992077, GM5T, C 6 71 BUT its a 5/8 in shaft-8 bolt flange.

Question: 1. Why does this have a 5/8 shaft?
2. Can I swap shafts and make the 3992077 work?

TheDucci

You can also buy a 5/8 to 3/4 bushing from summit. That is what I did for my BBC swap. I got the pulleys from a 74 but the aftermarket pump had the smaller dai. pump shaft; It worked great.

71LS5

I looked at the over depth of the two units and they are not the same. So its not just a bushing issue and fitment into the fan clutch its an overall shaft length issue as well.

zwede

Corvette BBC water pumps had 3/4" shaft. Other Chevy BB had 5/8". So the new pump did not come from a Corvette.

Mike Ward

No pump came from the factory with an 8 bolt flange. You have some weird generic rebuilt unit.

Paul L

And he needs a "short" pump.

71LS5

Can I use the parts at my disposal to make the this work? Are the castings the same? What is the difference between the two units. The casting on the 5/8 is the correct unit but maybe the shaft and flange changed?

71LS5

Ok I just verified that the shaft lengths are the same and the casing is the right one. It must have been rebuilt with the smaller shaft. Does anyone have an exploded view or can offer any advice on how to swap shafts and replace with new bearings and seals? I have not dismantled once before but I am sure its not rocket science

71LS5

Neither Ecklers nor Zip carries a rebuild kit for these pumps......still need to know about a shaft change out....

babbah

71LS5

Ok I think we all agree I need a "short pump". What does that really mean? I have determined that the pump I had was the 3/4 shaft which I understand to be the correct size for the corvette. I have also stated that the two units (the one I had which was correct but not the original casting number) was the same depth from block to shaft end/flange face. Lastly I also stated that the housings are identical except that the one I want to use has the correct date code and casting number but has the 5/8 shaft (see opening thread).

Knowing this why are all of you telling me I need the "short" pump?

When you say short what dimension are you referring to?

Can some one please help answer my questions

1. Can I swap shafts assuming I can get the right bearing and press it in using an arbor?
2. Are there any rebuild kits available for these anymore?

Tom454

Set the pump on the table legs down. Measure from the table to the face where the fan or fan clutch mounts. It should be 5-3/4". I have a new AC Delco #252-372 gm#12494121 sitting here and it has 8 holes.

Edit: the extra holes are for different fan mounting configurations.

71LS5

Hi Tom thanks for the reply! Ok so that dimension is what I thought is how we define "short" pump. Not exactly a geometric tolerance While I was going to measure that I alternatively took my level and put it on the face of the flange where the fan mounts and its level like I described above. I this this clearly indicates that I now confirmed they are the same. When I get home I will measure that dimension but I am sure its correct namely 5-3/4. With that out of the way we can get down to business.

Have a 1971 H20 water pump I want to rebuild and change shafts on.

Parts anyone? Shaft replacement is it possible? I have access to a hydrolic press

Tom454

Can't help you with sourcing parts... tried it a few times and dead-ended. There used to be a guy who rebuilt Corvette pumps for people wanting correct date coded parts... but I don't know if he is still in business. Someone else will have to chime in on that one. I picked up the AC Delco pump from Rockauto a few months ago for $75. It's $87 now.

Mike Ward

AC Delco has sourcing universal pumps for these cars on an off-shore basis for many many years. That's why your service replacement has 8 holes instead of the OEM 4 holes.

Bill Mock is the guy you're thinking of. He's still around.

gcusmano74

The 3/4 water pump shaft rides in a larger, stronger bearing. The Corvette used the same water pump as the "medium" trucks, C60's and such. If you put a 5/8 X 3/4 bushing on your pump, the pulleys will fit, but you will not have a heavy duty pump.
Get the right pump.

Tom454

The non-gm rebuilt one that I just pulled also has 8 holes... it was installed probably around 1986 when I bought the car. I think it's a conspiracy. But there's too many holes in it to succeed.

And yes... the box says "ASSEMBLED IN USA FROM COMPONENTS MFG'D IN CHINA, USA"

I can't find China USA on a map though.

ajrothm

Edelbrock makes a Victor series aluminum water pump that has the larger hole for 71' BBC vettes...

Also Stewart Warner makes the correct pump with the larger hole...

noonie

You have a bb short Corvette pump from a 1970 and earlier.
In 1971 the Corvette pump changed to a 3/4" pilot.

71LS5

Going a little batty here and trying to be upbeat..I love working on my Corvette...never drive it just work on it and throw lots of money into it.... OK some pictures from today might help some one else in the future. Hey that what its all about helping each other and keeping the cars together after all these years...42 years in fact.

I have the right pump from the casting number! Its casting number is correct however it may have been rebuilt for a different application......

Or its the wrong pump built for another application for lighter duty use with the same casting number?

Cant verify either....



Above you see the side by side and they are both short pumps as defined by Tom 5-3/4 tall measurement doh I mean short! (thanks Tom your helping me keep my sanity here




Here you can see this pump is dated in 1971 with the casting number I listed above and one that is documented for this car (as well as some other numbers used during this time frame).

Nope I am not an NCRS Judge but this is what I know to be accurate from my research. Is it possible for me to be wrong you bet...let me hear otherwise....from some one.



Here above you see what lurks inside. My initial unit dated 1974 but original pump on the left with the cast impeller. The one on the right rebuilt with a stamped impeller and possibly the wrong shaft (5/8). I got this from ebay from some one who claimed it to be for a corvette and rebuilt. Well the numbers are right but the devil is always in the details. The shaft is not right and the gasket looks old. The bearing and impeller maybe new but with a crappy gasket it tells me it was not done to my standards.

I measured the shaft size where the impeller looks pressed in and they both are the same diameter. So I maybe able to answer my own initial question. The shaft should be replaceable with the correct top bearing assuming I can get it out and remove the impeller and bearings. I would want to use the cast impeller on the 3/4 shaft where the cast impeller is currently thus making this exactly like what it would be like from GM.

So at this point I will work on dissassembly and see how that goes. If it goes well I will see if anyone responds here about parts but at this point either the guy or guys that know how to find the rebuild parts are not seeing this post or they don't exist. Is Lars here anymore or GDinia?