[mechanickeith]

Here are 4, 4 bolt pumps. For everyones info, 2 of these pumps are correct for the 4 cyl Tempest. One is correct for an early Pontiac V8 & one isn't worth the stamped steel it is made out of.

Notice that all 4 have the same casting number on them.

Looking at the impellers you will see the one that is stamped steel. This was purchased at NAPA & is incorrect for the 4 cyl's & V8's!!! The impeller is not the correct diamater or depth & will cavitate/bypass coolant & your motor will run HOT!!!


Next, look at the thickness of the impellers. You will see one that has much taller vanes & is sitting close to the pump housing. This is correct for a early V8.

Now for the Tempest 4 cylinder pumps!! Notice that 2 pumps have a shallow vane impeller & the impeller is off of the pump housing by about a 1/2 inch. This IS correct for our 4 cylinders. This different impeller sits further back in the timing gear/pump housing & only pumps the water that is in the back half of the housing. The back half of the housing is the half that supplies water to the right bank of cylinders. Our little 4 cyl motors use the same timing housing that is used on the V8's but the water pump impeller was modified so it only pumps water to the right half.

You can run a V8 pump in the 4 cyl & it will pump coolant & cool, but,,,, The motor is just wasting energy trying to pump coolant to a half of a motor that is not there. So, next time you have your water pump out, check the impeller!!!!!!!

Last but not least!!!! I have yet to be able to purchase a correct 4 cylinder new/rebuilt 4 bolt water pump from ANY parts house/supplier!!! What I have been doing is purchasing a V8 pump from NAPA, pressing the pumps apart & putting the correct impeller on the new pump!!!

http://www.kodakgallery.com/ShareLan...localeid=en_US

Keith

PS!!! The correct pumps are the first & 3rd!!