Old one versus new one. Obvious differences in the impeller assembly.



Comments appreciated.

Some say cast impellers are the only way to go. That they do a much better job keeping the engine cool. I don't know if they are better or not. My car has a stamped steel impeller, and it doesn't get hot very often. Maybe a cast one would do better--I dont' know. If it was me, I would put in the new one. I would think it would less likely to fail before the old one. If it doesn't cut the mustard in keeping the car cool, put the old one back on. It seems like the divider plate adjustment, which has been much discussed, has as much to do with pump efficiency as anything.

Keep the cast one. I believe the vanes are taller, and the gap less between the plates. If you recall I installed a new one and had issues...yada yada yada...I went with the GM cast style, and filed the vanes until they cleared the plates. I have a nice tight fit..Jee I like the sound of that...ok back to the subject...I think the stamped one will or could be more prone to less efficiency with a larger gap, thus allowing more coolant to bypass the radiator? Your 428 may run hotter than the 400 if your build it up, I would keep the cast one as my vote.

Also, does your cast pump have the GM part number on it? I recall the replacements, do not?

For me, and other Pontiac folks here that don't know, can someone set the record straight on how to identify the difference between CAST and how to identify STAMPED STEEL impellers.

I can assume the CAST is my original hunk of metal impeller, correct?

Your hung of cast is correct

hunk of cast...lol...

Correct, the cast one is your old pump. The stamped impellers look like they were made from a flat piece of sheet metal, and bent into the proper shape. I was looking at your picture, and I noticed that the cast impellers have six vanes and the stamped ones have eight. Also, the cast one looks to have a significantly larger diameter. I would assume these two things would allow the cast impellers to take a bigger "bite" of coolant as it spins. Again, whether or not you will notice any difference in performance between the two, I don't know.

There was a raging debate on Classical Pontiac about replacement water pumps a couple of years ago.

After lots and trial and error by many people over there, the consensus was to avoid the stamped impellers like the plague and adjust the dividing plates for a very small clearence like the discussion here a couple of weeks ago.

There were also comments that NAPA was a good source of the cast impellers but you had to go through many of the same part number to get one. I made sure when I purchased mine from Ames that the one I was going to get was cast. The salesperson pulled one off the shelf to check and then sent me that one.

Some people at CP have even gone so far to have a shop pull the cast impeller off their old pump and install it on a rebuilt one.

I can get brand new cast impeller (not rebuilt) for 11 bolt. I can check with my distributor for 8 bolt, if you like.

Well, it looks like I'll be buying an new 11-bolt Timing Cover for the new engine (since they are much easier to find), so I'll take the new 8-point pump back to NAPA. Vikki, what would your new 11-bolt pump cost?

They are cheap!
NOS;
http://cgi.ebay.com/ebaymotors/1969...itemZ160086266498QQrdZ1QQsspagenameZWDVW

You need to check this so your pulleys work. (fan hub to gasket surface distance 4.46")

http://store.thefirstgensite.com/servlet/Detail?no=27

These are new, not rebuilt or old stock, with a manufacturer limited lifetime warranty.

John, you may want to reconsider the change from 8 bolt to 11 bolt. There's a lot involved. Unless your hose necks are really corroded, just get the face surfaced and the holes chased, or I can help you with another 8 bolt cover.

For the 8 bolt, go to your local auto parts supplier and order this:

http://www.cardone.com/English/club/products/webcat/imageinfo.asp?PARTNUM=55-11137

Stay with the 8 bolt John, I had big pulley issues trying to change, and went back in frustration. Don't go there!

As for the impeller, they gave me a stamped one for the 11 bolt, and when I switched back to the 8, I got a cast unit. I also understand the stamped are more prone to corrosion and failure.

Yep, I completely forgot about the infamous pulley issues when converting.

I switched to 11 bolt and an early 69 (short nose) pump. With the 1968 pulley set, I had to use spacers behind my alternator and steering pump mounts. Not too cool. I'll change pulleys some day.

If you've got a couple hours, this is the mother of all water pump posts: http://forums.performanceyears.com/forums/showthread.php?t=411256

I remember that post Hammered! And George is right in the middle of it. Good link, thanks much.

Not only the pulleys are all affected - but so too are ALL of your accessory brackets and spacers.

Let's put it this way - since I am putting in a 455 and starting from a bare block (keeping my numbers matching 400 for prosperity) , I needed a timing cover and a new water pump anyway. I kicked around converting to the 11 bolt set up and them considered that all my accessories, brackets and spacers would not work. An FGF member got me a good timing cover and Ames got me a NEW 8 bolt WP with a cast impeller.

There you go. Either get every parts house in your area to open the boxes to check for cast or wait for one from Ames.

I posted a link a page back on how to get a brand new 8 bolt cast impeller pump locally:

http://www.cardone.com/English/club/products/webcat/imageinfo.asp?PARTNUM=55-11137

All you have to do is order it from your local auto parts store if they don't have it in stock.

Right. I saw that. But you never know what's going to be in that box...... They rebuild with original cast impellers 'when available'.

IT'S A BRAND NEW PUMP as I stated in both posts. There are no refurbished or used components.

Non original without correct part numbers then? That would have to factor into the decision. It may not look exactly like original. That would be the third option.

Correct. It's a brand new casting, brand new bearing, brand new impeller. It appears and functions as or better than new.

Do you look for the correct casting number and date when swapping in a rebuilt water pump? Odds of finding the correct one are, at best, slim.

I like to have the correct casting and casting number. The date is icing on the cake but you can't expect to find it. It's good to know that the casting is incorrect when making the decision.

If you're obsessed with casting number and date for concours purposes, have your original water pump rebuilt.

If you want a reliable and good performing pump with no core required and a long warranty, buy new.

Or take your chances and pick through the boxes at your local parts store for a rebuilt pump of unknown tolerances and limited warranty.

It's great to have a choice.

I'm not obsessed or concours. LOL Just like correct casting IF possible.

You left out Ames.

And chances are there is not a "bunch" of boxes to pick through unless you live close to one of the central distribution centers. I went to my local NAPA 1st and they had to special order an 8 bolt WP. Naturally it came with the stamped impeller.

Instead of repeating that process until the counter guy threw me out (luckily my next door neighbor), I just picked up the phone, called Ames and explained what I was looking for.

Ames is also a brand new pump. The topic of this thread was New Water Pump comparisons. I think a few good choices have been presented, especially for 8 bolt pumps.

I am still looking for a reliable source for short 11 bolt pumps.

Is this numbers matching water pump going on a 428!! in a 68 bird

To each his own sir. This info isn't just for one Bird, it's for all interested. Some may think it's important for their parts to have the correct casting numbers IF possible. And that doesn't make them obsessed. It just shows that some have different values from someone who just wants it to work good.

I am just picking on you Jim,
I agree with all your points. Nash should keep his numbers pump for the numbers matching 400. And put any thing that will work corectly on the 428 that will never be #'s matching.

Okay, its settled!

Now, everyone back to work again!