# Best aftermarket 389 (8 bolt) water pump?



## goatcheese (Mar 25, 2011)

Seems like I've narrowed my overheating problems down to the pump. Any of you researched the aftermarket for the 8 bolt pump?
Thanks, Brent


----------



## rickm (Feb 8, 2012)

there are many makers of waterpumps, most american pumps are good quality like trw, airtex, federal mogul. the most important thing is to install a pump with a cast impeller (stock style), not stamped steel. and of course, proper distance between pump impeller and plate like you must have read in an earlier reply. ive heard the flow kooler pumps work well. also i think edelbrock makes a pump now, not sure.


----------



## BearGFR (Aug 25, 2008)

Before you spring for another pump, try setting the plate clearance on the one you have. You may be surprised...


Bear


----------



## goatcheese (Mar 25, 2011)

I did take the water pump apart a couple days ago to check the clearance. I have the cast impeller. Gap was about 3/16". I tightened up to .035 or less but, didn't help. I did take my thermostat out and that didn't help. I borrowed my friends infrared thermometer since then. Cranked it up cold and observed both sides of the radiator and 6 points on the engine. As it heated up the radiator got to 190 on both sides and stayed there. Then engine remained consistent per area (heads, intake, etc.) and kept climbing. My temp gauge was right on with ir thermometer. Engine temp climbed to 230 before I shut it down. I do have a new t-stat in it now but, again it's been doing the same thing even without a t-stat. New lower hose with a spring. 5.75" water pump pulley and new aluminum radiator with 2 electric fans. I will check the timing again but, it runs great and if I remember correctly we set it at 8-10 degrees advanced. I'm out of town now so I'm thinking about it till I get home. I will take the t-stat out again and run it to pull temps with ir thermometer again to verify it to be the water pump.
I need to call summit but, in the catalog it looks like edelbrock only has an 11 bolt pump. I don't like the factory design with the little thin back plates. I'd like to get a pump that has a newer type of back plate design as well. If they don't have a such thing, maybe I'll start making them. Mine doesn't have the 2 tubes with grommet seals either. Appears it's not that design. I've read that about others as well.


----------



## the65gto (Oct 9, 2008)

Does your cast WP have the rounded vanes or the ones that appear to be milled flat on top like this photo


----------



## goatcheese (Mar 25, 2011)

Mine is not the ground flat veins. Must be older rounded ones? Were any of the stock 8 bolts ground flat or only aftermarket? Seems like there's more brands/options for the 11 bolts. Worth changing timing cover to 11?


----------



## BearGFR (Aug 25, 2008)

I just looked in the 65 Service Manual for the 8 bolt water pump and internal housing / divider plate. It wasn't obvious to me from the diagrams how it all goes together, but if it's similar to the 11-bolt setup in any way, it looks like the critical dimension for flow might be the smaller hole that's in the back of the rearmost "internal housing". That's the one that needs to be tight to the impeller vanes - just a gasket-thickness away from touching them.

Bear


----------



## the65gto (Oct 9, 2008)

Here is pic of original 11 bolt rounded vanes. I know that some of the vane variations do no extend to the edge of the rotating plate and some vanes are different height off of the plate. When you replace, you should re-check the vane to divider plate.


----------



## the65gto (Oct 9, 2008)

BearGFR said:


> I just looked in the 65 Service Manual for the 8 bolt water pump and internal housing / divider plate. It wasn't obvious to me from the diagrams how it all goes together, but if it's similar to the 11-bolt setup in any way, it looks like the critical dimension for flow might be the smaller hole that's in the back of the rearmost "internal housing". That's the one that needs to be tight to the impeller vanes - just a gasket-thickness away from touching them.
> 
> Bear


Bear, if this is what you are refering to??? the "internal housing" sits on a little ridge inside the timing cover, divider plate/gasket/water pump. Its difficult for me on why it was done like this.


----------



## goatcheese (Mar 25, 2011)

I have the 8 bolt rounded vanes. Are the replacement or aftermarket the milled flat vanes? Do any 8 bolt brands standout as an improved or model?


----------



## BearGFR (Aug 25, 2008)

the65gto said:


> Bear, if this is what you are refering to??? the "internal housing" sits on a little ridge inside the timing cover, divider plate/gasket/water pump. Its difficult for me on why it was done like this.


Right - that's it. Goatcheese the critical clearance is the spacing between the pump impeller blades and the plate that has the smaller of the two center holes. It's common for replacement/rebuilt/aftermarket pumps to have impellers pressed on at different distances, thus changing that clearance and requiring you to rework that distance when you replace the pump.

Bear


----------



## the65gto (Oct 9, 2008)

goatcheese said:


> I have the 8 bolt rounded vanes. Are the replacement or aftermarket the milled flat vanes? Do any 8 bolt brands standout as an improved or model?


This link will sit you down on page 1 of 61 so far. I would skip towards the end to find recent discussions about the Cardone pump. Seems that their engineering dept has developed "a special" pump for the pontiacs???? Anyways, I found it very interesting, took me two days to read thru the posts  Various engines, the tests and the results. I believe all variety of pumps are still out there as replacements, variations on cast and stamped. 

Chalk up one more for the cast impeller. - PY Online Forums


----------



## scoob (Jul 18, 2011)

Flowkooler works like a charm.:cheers


----------



## goatcheese (Mar 25, 2011)

Thanks Guys!


----------

