How old is the engine? as in is it the original build? Also check to make sure that you really have an A/C water pump, there is a difference and what I found was that when you order an A/C pump most parts suppliers will supersede the A/C pump and send what ever and it will most likely be a non A/C pump. The factory service manual will have the specs of your pump impeller that you need. I went thru a lot of hassle with my big block cooling when I found it to be the block was full of crap, I used the Mopar clutch fan with factory shroud A/C pump and flushed block, that car never bothered me again. It would run at a consistent temp in all traffic. My engine was a factory original with 70,000 miles in great shape cept for all the grud.
