98arcticwhiteT/A

so rockauto lists two part #s for the ac delco water pumps..anybody know the difference between these two besides the impellar one is $106 and the other is about $180..this is what rockauto told me

"Thank you for your email. The 251744 is the Original Equipment (OE) design with a steel impeller that Pontiac/GM used originally on the vehicle. The 252846 is the aftermarket replacement version with a cast iron impeller"

Marc 85Z28

iTrader: (8)

Seems pretty straightforward to me?

The pump with the steel impeller is a quality aftermarket unit, and you pay for it.

The pump with a cast iron impeller is a cheap aftermarket and probably has other compromises elsewhere to meet a price point. Take your chances...

demonspeed

iTrader: (7)

You'll also want to ensure if you're getting the updated pump which will require a new filler neck and separate thermostat (rather than the thermostat that's integrated in the housing like came stock).

DANOZ28

iTrader: (1)

i ran into this problem back when i changed my waterpump. they (gm) discontinued the ls1 pump so only ls2 was available for me. as the other poster stated i needed a diff housing which meant a diff 160 therm. new pump bolted up just fine. cheers!

98arcticwhiteT/A

talked to a GM dealer, ls1 pumps are updated which like you said is pretty much the ls2 pump..so I would need the ls2 housing and two new bolts..so does that mean I use the thermostat from the ls2 as well aka gto?