Machine Or Not To Machine
Thread Starter
Racer
Joined: Mar 2005
Posts: 306
Likes: 0
From: WAY SOUTH OF HEAVEN inebriated
Machine Or Not To Machine
I picked up a set of march performance undersize pullys for my big block and i was recomended to use a water pump with a 3/4'' shaft i got them up and realized the w/p pully center hole is 5/8 not 3/4 should i take it in for machining ? or get a different pump? switching the pullys is not an option . 
Burning Brakes
Joined: Apr 2004
Posts: 847
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From: Des Allemands LA
I would think getting a different pump is the only real option. Either a whole pump or change the hub on the pump you have now. I can't see doing weld build up and machining on the hub seams like that would be expensive. I also don't think I would trust putting a bushing in place as you would only have 1/16" on each side.
Melting Slicks
Joined: Jun 2002
Posts: 2,844
Likes: 99
From: Orrtanna Pa.
It seems to me that the Corvette water pump (with the 3/4" shaft) is a bastard length pump. It's in between the other Chevy short and long pumps in lenght between the block and pulley mounting surfaces. I'd check this to be sure before you drill a new pulley. I changed my water pump to the standard Chevy short pump when I did mine.
Mine is a small block though.
Mine is a small block though.
Last edited by The Money Pit; May 28, 2005 at 04:25 PM.
Safety Car
Joined: Feb 2002
Posts: 4,286
Likes: 4
From: Guam
I would call March Performance and talk to them. If I remember correctly, there is a difference in offset on the hub of the 3/4 pump. So if you merely machine out your pulley, you might end up with the pulley being misaligned. Then you would have another problem and have to use spacers....But like I said, I am not sure if they are different, but you should check to be sure. You could get both pumps and compare. But then again, if you are going thru all that trouble, just use the correct one that March Performance reccomended.
Thread Starter
Racer
Joined: Mar 2005
Posts: 306
Likes: 0
From: WAY SOUTH OF HEAVEN inebriated
Does anyone know for sure if there is a difference in offset on the hub of the 3/4 pump compared to a 5/8 shaft size pump i dont have my engine here yet its still at the farm waiting for other parts.but this info would save me weeks of time thanks .
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From: Toronto Ontario
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I had the same problem. I have the March serpentine kit, and I at first had the Corvette specific Edelbrock Victor water pump with the 3/4" shaft. I comtemplated drilling the pulley out, but in the end decided that it was better to change the water pump because I didn't want to have any problems as a result of doing so.