Water pump pilot shaft diameter confusion.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 107
Likes: 0
From: Bolingbrook Illinois
Water pump pilot shaft diameter confusion.
I ordered a set of aluminum pulleys for my crank and water pump (I have a '78 L-82 with A/C) off of ebay. I got impatient and did the buy it now without confirming fitment. The seller is happy to work with me to get what I need but now I am not so sure. My steel water pump pulley has a 3/4" dia center hole, the new one has a 5/8". I figured I could open the hole but the bolt circle for the new aluminum one is smaller than the bolt circle on the old steel one. The height on both of them appear the same so I am pretty sure I should have the "short pump" version.
What am I missing?
Thanks in advance for the input.
I forgot to mention that the car has an Edlebrock Performer water pump (that the stock pulley fit on).
Racer
Joined: Nov 2000
Posts: 290
Likes: 0
From: Omaha, NE
The 71-82 Corvette small block water pump was unique to vettes and a few medium and light duty trucks. All the bolt patterns and pilot size was different. Aftermarket pumps will have a dual bolt pattern and a pilot shaft bushing.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 107
Likes: 0
From: Bolingbrook Illinois
I recall the hub of the water pump having two sets of mounting holes for the pulley. When I get home tonight I will check to see if the holes line up with the new pulley. If they do, then I will just open the hole.
I will post later with the results.
Thanks for the input.
I will post later with the results.
Thanks for the input.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 107
Likes: 0
From: Bolingbrook Illinois
The second set of mounting holes on the water pump match the new pulley. I am going to ream the hole to 0.750 and put on the new pulley.
BTW, Hotzone Performance is a superb ebay seller.
Thanks for the input.
BTW, Hotzone Performance is a superb ebay seller.
Thanks for the input.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 107
Likes: 0
From: Bolingbrook Illinois
Yes, you are correct.
My dilemma is this: the lathe is tied up for the next 6 hours, the CNC machine is open. I will circular interpolate the bore on the CNC to 0.745 dia and then ream to final size to keep it pretty.
Its a clearance hole but you cant overdo your Vette, right?
In fact, I will go check on it right now as it should be done!
My dilemma is this: the lathe is tied up for the next 6 hours, the CNC machine is open. I will circular interpolate the bore on the CNC to 0.745 dia and then ream to final size to keep it pretty.
Its a clearance hole but you cant overdo your Vette, right?
In fact, I will go check on it right now as it should be done!
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Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
Might have been cheaper/easier to swap out the waterpump with a standard short pump.
When I replaced my water pump, I got a short chrome plated one. Also ordered chrome pulleys. Both were 5/8". Really dont understand why the vette "needs" the 3/4".
When I replaced my water pump, I got a short chrome plated one. Also ordered chrome pulleys. Both were 5/8". Really dont understand why the vette "needs" the 3/4".
Pro
Joined: Jun 2005
Posts: 581
Likes: 60
From: USA
it DEFINITELY centers the pulley, and if the pulley's spinning at 5,000 RPM and higher, you need to get that sucker dialed in right-on, like in the range of thousandths. Otherwise, I could see that that the high-RPM out-of-balance could cause premature water pump bearing failure, possible thrown belts, just general mayhem.
