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Water pump differences


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I replaced the water pump last night on my 350, and was dismayed to find (after I'd painted it) that the alternator bracket boss on this pump is approximately 3/4 inch closer to the radiator than the old pump. What's going on here? I thought all smallblock pumps were the same. My engine is a 1986 fuel injected block, if that makes a difference. I asked for a water pump from a 1974 Nova, thinking they were all the same. The alternator bracket and original water pump were from a 1984 Camaro 305.

 

Can someone help educate me?

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There were two styles of small block chevy water pumps (excluding the new LT-1) that I know about, a short and long style water pump. I thought the short was for 68 and below, the long for 69 and up. I believe the difference was about 3/4 of an inch as well. I know you can buy spacers for the short one, but it sounds like you have the long style.

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There are quite a few different water pumps. Short pumps with 5/8" pilot for Corvettes through '81, short pumps with 9/16" pilot for pass cars through '68 and trucks through '72. As you have found out, early and late style long pumps. Aluminum pumps like the '84 Corvette that is a short pump but a different dimension block to pulley than the earlier short pumps. Then throw either standard rotation or reverse rotation into the mix if you have serpentine drive. As you can tell, whatever accessory drive you have dictates the pump you need.

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Can you weld on a piece of steel and drill a new hole?

 

I could, but since the pump was a whopping $18.00, I'd probably just buy another one instead just to keep from going through the trouble. Since the new pump already has a boss on it (but in the wrong location) I'd have to grind that one off before I could weld the new one on. Major PITA.

 

Thanks for the suggestion, though!

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