Join Date: Jul 1999
Location: Colleyville, TX
I posted a topic several months ago regarding this subject. Kurt S. and Jonesy were kind enough to reply. However, I am still confused and need further assistance.
Anyone out there with a 396-375 hp with a short water pump?
My main question is what is the diameter of the crank pully?
I have a water pump pully that is about 7-1/8" in diameter and have been told by Kurt S. that the water pump pully should be 7.1" I think I have the right water pump pully but it is not stamped with the any numbers. The correct number should be 3906656.
I also have a two groove crank pully with the number 3874414 stamped into it. Kurt S says this is for a '68 BB w/ A/C. The diameter of this pully is 7-3/8". Kurt says the correct pully would be a 3869978 three groove pully.
At his point I am not as concerned about the correct numbers as I am about the correct diameter.
I thought I would be able to use the above mentioned crank pully with my 7-1/8" water pump pully. Here is the problem, they will not fit into their respective areas without interfearing with each other.
I measured about 6-7/8" between the centerline of the crank and the centerline of the water pump pully. As you can see, if I take the radius of my two pullys and add them together I come up with a centerline distance of 7-1/4". Should my crank pully be smaller? Maybe the water pump pully is incorrect?
If the crank pully is smaller than the water pump pully then the water pump will be turning slower than engine speed.
I do not want to turn the water pump too slow and overheat the engine.
Any help would be much appreciated.