RanBurVette

I am installing a new A/C condenser and will be changing water pumps
at the same time. Want GM part number for a LS3 pump that will interchange with a 1998 LS1. Do I need a thermostat housing and stat
to make the swap. Assuming the drive belts are the same. Anyone made
the swap? LS3 is a better pump. Any help will be much appreciated!!!!!
THANKS

bullitt4110

A LS1 pump will work just fine, but if you really want a LS3 pump the only thing that might be different is the thermostat housing, some of the eariler LS1/6 had the thermostat and housing as one piece and the later ones are seperate. Your belt and tensioner should work just fine.

trackboss

Do the replacement water pumps have the short pulley? The original on my '99 uses a generic pulley that works on all the LS motors with various accessory drives. I'd prefer to use a short pulley reduce weight and free up some space.

C5Spirit

General information:

Remember the water pump gasket thickness is different than the LS1 water pump if you go to a supercharge later this is a need to know because it will throw the alignment off and the belt will walk over one rib. In my case that is what it did. My .02

trackboss

Any reason I couldn't just use the early gasket? I have never heard anything about the thickness. Will never go supercharged so I'm not worried about that.

RichieRichZ06

The part number for LS3/LS7 pumps are the same. 89018052.

After late 2003, the pump housing changes where the t-stat goes and it is a different size. The later pump will work, but will require the newer style housing if ever replaced.

C5Spirit

I believe it's because the T-stat housing is different.
I believe Richie can give you the gasket part# for the LS1 water pump gasket and it will be different than the LS3/LS7 gasket.
I think the LS3/LS7 gasket is .060 thicker...or the other way round. But as you said no worry for you because you won't be going to a supercharger...

trackboss

I'll have to measure the gaskets for myself. They don't appear to be any different in the packaging. Hopefully I won't have any belt issues. I don't have any ls1 gaskets available (assuming they are different) and would rather not do this twice. I can't see any reason why gm would make such a change. The pump is noticably lighter than my original which is really nice as is the smaller pulley to free up some much needed space.

C5Spirit

Myself and Andy at A&A can tell you there is a difference in the LS1 and LS6 water pump gasket, because we had an alignment problem with the Vortech supercharger to the point that Andy has put this information in his installation instructions. LS 3 water pump may be entirely different.

trackboss

Ok, I'll try to remember to take some measurements. Is the belt best centered on the water pump with the included gaskets or with the old LS1 gaskets?
-V

C5Spirit

I'm only guessing but I'd say centered...someone will chime in I'm sure with a correct answer if I'm wrong..

trackboss

With which gasket?

trackboss

I measured the included gaskets and they average .065" total thickness. That is about 1/16" of an inch. When I get to my old pump I'll measure the difference in gasket thickness as well as set the pumps next to each other and see how the pulleys align.

trackboss

I put both pumps side by side on a flat surface and took some measurements. This is what I found:
My original LS1 pump has a wear stripe on the pulley indicating the belt is riding right along the back edge of the pulley. There is about 3" of pulley forward of the belt not being used. GM did this in order to use one pulley for multiple accessory drives (corvette, camaro, truck, etc.)The original (used/compressed) gaskets are roughly .060" thick. The back edge of the LS3 pump pulley vs. the LS1 pump pulley is about .094" closer to the mounting surface (gaskets excluded). Using the LS3 pump with the included .065" (new) gaskets puts the back edge of the pulley .089" closer the engine. Using the early gaskets puts the back edge of the pulley .094" closer than the original pump. By looking at the wear strip the closer to the engine the pump is the more centered the belt will be on the pulley. However, regardless of gasket the LS3 pump allows the belt to ride inward of the back edge of the pulley which is a good thing. In all, the gaskets thicknesses are extremely close and should be a non-issue. I have not looked at a vortech setup to see how sensitive the pulley alignment is, but keep in mind the back side of the belt is what rides on the water pump pulley because of it's reverse rotation and in most cases it is not nearly as sensitive to belt alignment as any of the ribbed pulleys.