[72firechicken]

Alright, I have some input too. First I have purchased three pumps.

1st one from Auto Zone and it had a stamped steel impeller.

2nd one from Pep Poys and it had a cast iron impeller But I found that it is a much smaller in diameter than the stamped steel one and the fins were not very tall.

3rd one is an A/c delco from a delco supplier in my area and finally this one has a large diameter tall finned cast impeller like it is supposed to be.

I have also found that GMB makes a pump that is to exact oem specs. Like the A/C Delco.

I have tried the first two.

The one with the stamped impeller worked o.k but the car ran at about 202 deg. at cruise which is why I have started trying the different things mentioned in this article. The rest of the cooling system is in great shape this I know.

Sooo, I next tried the Pep Boys pump which has a noticeably smaller diameter and fin depth impeller and the car ran hotter especially at idle, alot hotter than ever before I had only changed the water pump and clearenced the fins by "adjusting" the water divider plate as described in this article.

Now that I have found a correct style impeller I will try this one with properly clearenced fins.

So thre different pumps and three different impeller designs.

[grandville455]

How big around was the diameter on the 2nd one as i just bought a different one too and it looks smaller also?

[soupman]

If you look at the stamped steel impeller, there are big voids between the vanes. The cast impeller doesnot have these voids or big spaces by the shaft. I believe these voids contribute to cavitation, therefore effecting circulation of the coolant.

[george kujanski]

Looks like the hot Pontiac engine puzzle is finally coming together. No wonder a lot of engines are running hot with the variations of impellers and clearances out there. I'm starting to wonder if the rebuilders work to any specifications at all.

From what I've seen and read here, at least for a '67 motor, the proper design is what Charles (Old Goat) finally found. Can't beat those taller, cast fins. Anything else will not work as well.

Other, later engines, a cast impeller, minimum clearance. That's the ticket!

George

[JoeF]

I may be wrong, but my guess is that many of these rebuilders reinstall whatever impeller was on the pump when theye received it (as long as it's still good). I think that may be why we see some incosistencies when ordering. i.e. Two (or three) pumps from the same rebuilder that are all different. It would be great to know a way to get exactly what you want the first time.

[george kujanski]

I wonder if a stamped impeller ever was OEM. I would think it's more likely a rebuilder part to replace a corroded impeller & therefore be able to save the pump for resale; otherwise he would have to trash the whole thing. I suspect Over the years these things got into the parts pipeline.

George

[6t7gto]

i drained the CLR out last night. noticable improvement just looking inside the radiator.filled it up with water, took it for the same spin i did on sunday, and my water temp was 165. it was 190 on sunday before the flush. both days it was 50 degrees outside. now i have to flush it out real good to get all the CLR out. put the 160 thermastat in and see what happens.
david

[Old Goat 67]

Guys, I want to say how impressed I am with "you all's" diligence. This will surely help others in the future. I will be out of it for the weekend, have to get my last son married!..gotta put on a penguin suit. Check with you all on Sunday.
Charles

[grandville455]

Ok I measured my new pump's impeller ..It measures 3 3/4 edge to edge and is 5/8 tall does that sound about right ? for my 74 455.... Pics to follow later

[rudytadow]

6t 7 gto,
I will be replacing my water pump in a few weeks. I have all new everything - hoses,t-stat. Where did you pour the CLR in? How did you go about flushing it out? Did you leave the cap off during the flush?
Rudy

[rudytadow]

6t 7 gto,
A few more questions. Did you leave the coolant in with the CLR or no? I'm one of those guys who needs the step by step instructions. An engineer during the day. a weekend mechanic at night. I'm a stickler for detail so bear with me. I've already gone though more new collant than I wanted to, a water pump and now am having my original pump rebuilt just to do it all over again. I already did the bypass since I trashed the heater core on the last flush with just running water through the radiator with the car running. What is the purpose of the high idle for an hour vs normal rpms?
Thanks.
Rudy

[grandville455]

Here's those pics

[grandville455]

one more

[george kujanski]

Grandville, can you take another shot of the first pic with the fill flash on so we can see the detail of the impeller?

George

[can_am4me]

Just finished getting my Can-Am on the road today. The old 400 had been running hot for the last three years, so I was concerned when the 455 was going in this year. I was sure glad to run across this thread! Went to Checker Auto, and had them bring all the Pontiac water pumps to the counter, and I found one with a nice large cast impeller (my old pump had the "alternator" style blade). Hammered the seperator plate till the gap was less than .030 inch, and bolted it all up.

Fired it up today, a nice 70 degree day, and the temp never got above 175! Prevoius temps were near 220 all the time.

It finally occured to me that the only thing that I changed three years ago was the water pump! But you never think that the pump is the problem, so you never give it a second thought. Problem solved.

By the way, the good pump was in a box labeled "GMB" .

[grandville455]

here ya go george

[george kujanski]

Grandville, I don't see a pic.

CanAm: good to hear!

George

[grandville455]

I know didnt work ,lol

[grandville455]

George u have mail!

[denden 68gto]

I bought the cardone pump,the divider plate has a clearance of.60 after tweaking and took the car for a run.Ran about 180 on the road,stopped at the post office and left the car running, my brother was in it,came back out in about five minutes and it was up to 195.Drove it toward home and it cooled down to 180,stopped by a stoplight for two changes of the light and it was back up to 195 and climbing.this was on a beautiful 70 degree day in Indiana.Last summer it would have taken temps above 80 to do this.For me this did not work,actually it is worse.