I have a 65 Cutlass with a 425 (year ?) and its pretty tired , I have a 455
(1970) that came with the car . I might toss in the 455 and see how it does, anything to be careful of or look out for ?
Seems it would be a straight forward swap ? thanks!

 

They are the same externally

 

Balancer on the front and flexplate/flywheel are different. Different water pump snout lengths for different year ranges.

 

Go for it, and good luck.

 

The water pump length varies due to A/C or non-A/C. It is not related to year or engine size. Use the pump that matches the brackets and pulleys you plan to use.

 

My experience has been that in 66, for example, all water pumps are about 5.12" height; AC pumps have a .75" diameter circle near the pass side port. I think it was about 68 when Olds went to the 5.62" height.

 

Thanks guys , I am pretty sure both engines have pulleys on them .
So I should be able to "drop" in 455 but if nec. steal parts of the 425 ?
I am not worried.
Now the important stuff run headers ?(got em) Run the 2 spd . till it dies?
put in the T350 at the same time ? (not real hot on adding the floor shifter)

Just stuff for me to figure out !

 

The difference in water pump heights is a function of A/C vs. non-A/C. It is not generally related to the year. The pump height is matched with the brackets and pulleys. Use them all as a matched set.

 

Joe, if you get to NM or NV, I will show you some AC pumps for 66 that are 5.12" high, just like the non-AC pumps. I don't know much about any other years. Since I never use AC pulleys either, I suppose it is possible Olds used 5.62" pumps then but the GMPD parts book doesn't list anything but the 5.12" high pump in 66 (388182 regular, 388183 AC).

 

Actually, the A/C pump is also the HD cooling pump. My W-30, for example, uses a long nose "A/C" water pump in a non-A/C application. I was simplifying my response (since I'm lazy ), but my response remains the same: Use the pump, pulleys, and brackets as a matched set.