C3 3782608 Waterpump hub wrong diameter

[Jimmy B.]

Ok all you back yard mechanics I need some help. Got my rebuilt waterpump installed on my rebuilt 350/350 engine for my 69 and I discovered when I went to bolt on my fan pulley the holes did not line up on the hub, and this hub was larger than my original. I have a used wp with the correct hub staring me in the face.

Can I take a gear puller and remove the hub off the spline/shaft of my new rebuilt waterpump, take it to a machine shop and get the old hub off the other used waterpump and press it on the new shaft and all is well or I am up the creek without a paddle? This is starting to really $%^&* me off!!!

For all you snow boarders it is 75 deg. here in sunny Florida. I knew there was a reason I moved to this mosquito/alligator infested state. I hope the 8 foot gator that lives in the lake behind my house doesn't come into my garage to offer assistance or I might have a good deal on some "gatorbacks" for some one.

Thanks for all help and any recommendations.

Regards,

Jim Blakely

[Gene M.]

Re: C3 3782608 Waterpump hub wrong diameter

Jim,
You can go thru all the pressing off and on if both shafts are the same size. At some point in C3's GM went to a bigger diameter shaft on the water pump. Make sure the flange ends up in the same place. When pressing back on be sure to remove the back cover and back up the shaft. Do not press against the cast housing.

Be sure casting is correct configuration because if not the pulley will not clear the casting.

[Jack H.]

Re: C3 3782608 Waterpump hub wrong diameter

The change date for the water pump hub was 1971 (small hubs with small bolt pattern prior to '71).

Jimmy, the advice Gene gives you regarding removing the back of the water pump and supporting the impeller during pressing the replacement drive hub onto the water pump shaft is DEAD ON! Plus, you need to know the correct distance to press the replacement hub on or you'll have a pulley/belt mis-alignment.

The good ole boy here in Denver who we used to overhaul water pumps will NOT re-use a pump shaft that's had a hub pressed onto it before. It's his judgement that this is an interference fit and once a hub has been pressed onto a shaft, neither the hub or that shaft are safely reuseable again.

I know there are many who disagree, but this is your decision. Why not go back to the guy who rebuilt your water pump and have HIM make good on the job? You paid for a correct overhaul and didn't get it....

[Joe L.]

Re: C3 3782608 Waterpump hub wrong diameter

The change date for the water pump hub was 1971 (small hubs with small bolt pattern prior to '71).

Jimmy, the advice Gene gives you regarding removing the back of the water pump and supporting the impeller during pressing the replacement drive hub onto the water pump shaft is DEAD ON! Plus, you need to know the correct distance to press the replacement hub on or you'll have a pulley/belt mis-alignment.

The good ole boy here in Denver who we used to overhaul water pumps will NOT re-use a pump shaft that's had a hub pressed onto it before. It's his judgement that this is an interference fit and once a hub has been pressed onto a shaft, neither the hub or that shaft are safely reuseable again.

I know there are many who disagree, but this is your decision. Why not go back to the guy who rebuilt your water pump and have HIM make good on the job? You paid for a correct overhaul and didn't get it....

Jack-----


I completely agree with that "good 'ole boy"; he's got it right. The shaft, itself, could probably withstand multiple installations of a hub. However, in most cases, the shaft/bearing assembly will not be re-used, anyway. At least, if I remove one from a waterpump I'd never re-install the same one REGARDLESS of whether it might seem like it's "good".

The real problem is the hub. This is where the interference fit is "taken up". Upon re-installation of a USED hub, 2 things happen:

1) The original interference fit is lost;

2) Excessive runout on the face of the hub is OFTEN created. This causes TOTALLY UNACCEPTABLE pulley "wobble".

To some degree, the problem described in (1), above, can be ameliorated by "staking" the bore of the hub and using Locktite Anaerobic Sleeve Compound (green). However, this just exacerbates the problem described in (2), above.

[Joe L.]

Re: C3 3782608 Waterpump hub wrong diameter

Ok all you back yard mechanics I need some help. Got my rebuilt waterpump installed on my rebuilt 350/350 engine for my 69 and I discovered when I went to bolt on my fan pulley the holes did not line up on the hub, and this hub was larger than my original. I have a used wp with the correct hub staring me in the face.

Can I take a gear puller and remove the hub off the spline/shaft of my new rebuilt waterpump, take it to a machine shop and get the old hub off the other used waterpump and press it on the new shaft and all is well or I am up the creek without a paddle? This is starting to really $%^&* me off!!!

For all you snow boarders it is 75 deg. here in sunny Florida. I knew there was a reason I moved to this mosquito/alligator infested state. I hope the 8 foot gator that lives in the lake behind my house doesn't come into my garage to offer assistance or I might have a good deal on some "gatorbacks" for some one.

Thanks for all help and any recommendations.

Regards,

Jim Blakely

Jim-----


I don't understand how you could have a hub that's not usable. Original "4 bolt hole" hubs are usually smaller in OD than replacement "8 bolt hole" hubs. However, the latter hubs will fit perfectly in any Corvette pulley. So, from that perspective, the hub should present no problem, at all.

As far as the bolt pattern goes, the replacement hubs with "8 bolt holes" are a DUAL PATTERN HUB. They have both a 1-3/4" and 2-1/4" bolt circle patterns. One or the other of these patterns was used for EVERY Chevrolet V-8 engine ever made between 1955 and 1982 and most of those made well after 1982. In fact, I believe the same bolt patterns were used for many Ford and Chrysler applications, too.

So, it's hard to imagine that you have a hub with a bolt pattern that's incorrect.

There's ONE possible exception, though. This would be a hub with a SINGLE PATTERN, 2-1/4" bolt circle hub. Some original 71-82 Corvette waterpumps use this type of hub. However, these fit only a 3/4" shaft and could not be installed on your 5/8" shaft pump. It's possible, I suppose, that there were 2-1/4" single pattern hubs made for 5/8" shafts, but these were never used on a Corvette.

So, the bottom line is do you have a dual pattern hub or a single pattern and, if it's a single pattern, what is the bolt circle?

[Jimmy B.]

Re: C3 3782608 Waterpump hub wrong diameter

I have a single 4 bolt hub and it's around 2 1/4" center to center bolt hole. I'm taking both waterpumps and correct upper pulley to my engine rebuilders/machine shop tomorrow so they can mike and tell me we can switch hubs or it's back to the drawing board.

Thanks to all who responded.

Also just discovered my new DELCO 10 1/2 clutch I've had in a box under my bed for over a year and a half will not fit the bolts holes in my 11 in. flywheel. Now I'm really getting $%^&* off!!!

As the "late" Paul Harvey would say "Have a nice day"!

Jim

[Joe L.]

Re: C3 3782608 Waterpump hub wrong diameter

I have a single 4 bolt hub and it's around 2 1/4" center to center bolt hole. I'm taking both waterpumps and correct upper pulley to my engine rebuilders/machine shop tomorrow so they can mike and tell me we can switch hubs or it's back to the drawing board.

Thanks to all who responded.

Also just discovered my new DELCO 10 1/2 clutch I've had in a box under my bed for over a year and a half will not fit the bolts holes in my 11 in. flywheel. Now I'm really getting $%^&* off!!!

As the "late" Paul Harvey would say "Have a nice day"!

Jim

Jim----


I assume you mean a 14" flywheel for an 11" clutch; there's no such thing as an 11" flywheel for a Corvette. Usually, 10-1/2" clutches are designed for use with 12-3/4" flywheels. However, they will also work with a 14" flywheel IF THE 14" FLYWHEEL IS DUAL-DRILLED. Some are, but, apparently, the one you have is not. I DO NOT recommend attempting to drill a 14" flywheel not originally dual-drilled for a 10-1/2" clutch.

[Clem Z.]

Re: C3 3782608 Waterpump hub wrong diameter

i have removed and replaced the same hub on water pumps with no problems. remove the hub have the correct bolt pattern drilled and tapped and then have it pressed back on.

[Jimmy B.]

Re: C3 3782608 Waterpump hub wrong diameter

You're correct on the flywheel Joe, it is only drilled once. Also it has a cast date of HXX9 on it and my car is a Sept. 69 build. Thanks for all your help.

I am taking my waterpumps to the machine shop tomorrow to see what they say.

Regards.