Water pump Impeller size

[david shafer]

While changing the water pump I see that the new one has a cheap looking stamped metal impeller. The housing is a nice new aluminum piece though.
Looks good except for the impeller. Could I, Should I pull the heavier cast impeller off the old one and press onto the new? New is 3 and 1/2 ... old
is more than 4 inches in diameter. I have had it in reserve too long to exchange. It's a 403 engine with 90,000 miles.
Thanks
Dave

--
1977 26 foot 403

 

[Ken B]

I contend that you should keep the higher capacity pump, meaning larger impeller.

That same casting was used on multiple engines but the impeller size was changed. Ours came with a 4-1/8" or 4-1/4" for a reason. Some report having
problem getting the air out of the coolant going heater. I have never had that problem with the higher flow 4" or larger impeller.

Others here claim that impeller size makes no difference. So this is just my different opinion.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[terry1]

I'd say that if you have the necessary tools and knowledge, and the parts will fit, do the swap. Unless you are on the side of the road or in a hurry
to get it going again. It's only a water pump, and if you want to fool Murphy's law, get another new one as a backup in case the swap operation goes
south. Somewhere on this forum the correct part# for the larger impeller pump is sure to be declared, but I don't know where that is yet. Others may
be able to zero in on it easily.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.

 

[Ken B]

If you need the NAPA part number for a large impeller pump, I have one new in the box either here in my basement or in my hangar at the airport. I
can go find it if necessary.

I believe that you want to switch impellers on the one that you have, not buy another one.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Jim Hupy]

I did a rally tech seminar on water pumps. I purchased 5 water pumps, using
the same part number from 5 different sources, including Applied GMC. Which
Jim provided at no charge. 4 of the 5 had the incorrect sized impeller.
Guess which pump was correct? The one from Applied GMC was correct. Remove
the old pump, take it with you to your vendor, and take your chances, or
make the Call. Your choice.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

If you need the NAPA part number for a large impeller pump, I have one new
in the box either here in my basement or in my hangar at the airport. I
can go find it if necessary.

I believe that you want to switch impellers on the one that you have, not
buy another one.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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[david shafer]

Right Ken, I found lots of good info (some conflicting of course) on the forum. For example:

http://bdub.net/gmcmotorhome.info/watpump.html

But since I have this one... and it's pretty ... I think I'll try the impeller swap. Thanks for your offer to look up the part number. It is in the
link above. And thanks to both of you for your imput.

Dave
--
1977 26 foot 403

 

[kosier]

There is no number for a large, cast iron impeller, water pump because they
are no longer available. However, Flowkooler does sell
a rebuilt pump with a large aluminum impeller. I wonder about the long term
impeller durability of the aluminum impeller, but what
do I know? Many years ago, I worked on a Ford that overheated after warm up
after the second water pump. After we replaced every-
thing else under the hood (at Ford's direction) the third water pump fixed
it. There's more to the story, of course.

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
Fro(m: "Ken Burton"
Sent: Monday, January 29, 2018 9:39 AM
To:
Subject: Re: [GMCnet] Water pump Impeller size

> If you need the NAPA part number for a large impeller pump, I have one new
> in the box either here in my basement or in my hangar at the airport. I
> can go find it if necessary.
>
> I believe that you want to switch impellers on the one that you have, not
> buy another one.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[roy keen]

Had a problem with a flow cooler pump as the engine tended to run hot with it. So I returned it to Summit and put the stamped steel impeller pump
back on the engine and it ran cool again..
--
Roy Keen
Minden,NV
76 X Glenbrook