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Thread: 6.5 water pumps

  1. #21
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  2. #22
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    Mr. Fuller is/was a training instructor. He can offer some good insight. However, his comment about the "coolant flows through the engine with no restriction whatsoever and travels too quickly to absorb enough heat" is not sound from an engineering perspective. Faster fluid flow is associated with increased convective heat transfer coefficient which means increased transfer of heat through convection from the cast iron surfaces to the coolant. I've heard this "old wive's tale" before. It simply doesn't make any sense.

    The reason that you shouldn't leave the thermostats out is that to perform best with highest efficiency, the engine operating temperature should be regulated to the design specification. That's what the thermostat does.

  3. #23
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    Quote Originally Posted by ronniejoe View Post
    Mr. Fuller is/was a training instructor. He can offer some good insight. However, his comment about the "coolant flows through the engine with no restriction whatsoever and travels too quickly to absorb enough heat" is not sound from an engineering perspective.
    Very diplomatic!

    The same logic would argue that, to keep cool in the summer, you should run your fans as slow as possible so the air has more time to absorb heat from your body...

    One other thing that some thermostats contribute is blocking off the bypass passage as the engine temperature increases, forcing more coolant through the radiator.
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

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  4. #24
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    Glad to see very like minded conversation about the two HO pumps. I too have heard that the spin on pump is balanced flow and argued the point that there is no proof of that. I need to see some proof myself that it does flow any different than the 4-bolt pump.

    My current logic is the spin on pump was just an industry change that favored that design is all. I think that change is impractical, as I like the 4-bolt setup as it's easier to service for me, at least with common tools.

    I've been studying the water pump designs like pictured in these postings this year myself, mainly to gain a better understanding of design changes. The study came about in justifying and seeing the function behind the Peninsular v-belt water pump that I now own the tooling for.

    I got the misfortune recently of having to produce a new pattern for the cast iron impeller wheel that goes into the Peninsular pump, so I had to justify the engineering behind it and of course the economics of production to continue the item.

    The design engineering spec sheets call for closing the gap between the impeller and the housing. In looking at an 80's v-belt AC Delco pump, I can clearly see why they did it (lots of gap similar to the 80 gph serpentine pump pictured in these threads). I too am behind RJ's engineering on a smaller gap being ideal. Other than the wheel being larger to fill the void the wheel has some other design changes.

    This coming summer I am considering doing a test with a variable speed DC motor with the water pumps. have to machine pulleys for the motor and pumps tho...

    Anyone know what the RPM the pumps form their rating? For example at what RPM does the HO pump produce approximately 130GPM?


    J

  5. #25
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    The spin-on fan clutch design was done purely for speed of assembly during production, plain and simple. There is no performance difference at all, but they save time during assembly. It makes service more difficult, but that really isn't a concern for the decision makers.

  6. #26
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    Default Dig a little deeper

    OK, I've been watching this thread and waiting for someone to take it a step farther and bring up the fact that there is TWO spin-on fan AC Delco HO water pumps.
    '97 - '99 trucks spec out to a P/N 252776 or 88926290.
    2000 and newer 6.5 truck and other applications call for a P/N 251603 or 12456231, 19168609 or 88894035.
    Both are HO spin-on fan water pumps. Except the 251603 is $120 more roughly and it carries claims by the over-industrious (in my opinion) 6.5 aftermarket crowd that it is THIS ONE that is balanced!!!

    My mind is blown on this thing! I have bought both...the '99 version is still hanging on my truck on the 2009 6.5 Optimizer I just installed (tested) used and turned out to be a dud!
    I don't see a difference in the new GEP take off I bought 5-6 years ago from Peninsular and had on my GM block for 3 years. By the way, when I pulled it off the impeller had signs it was rubbing the backing plate and had some radial play in the bearings. So it did not get re-installed with only 20,000 miles on it.

    I've been a 6.5 owner for 21 years now continuously and have seen a lot of products and claims made for and about the "performance" upgrades of this and that. There are core improvements that can be made to increase user satisfaction to be sure. Cooling is one of them. This "balanced" water pump thing seems unsubstantiated when it comes to one spin on fan HO water pump to another. Likewise, I can't believe the bolt-on 137 GPM pumps are any different.

    Now.. I just need to finalize the deal to get a good (new I hope) long block from the seller I'm working with who sold me the dud, and who shall remain un-named at present, and redo all the gut-wrenching, sleep losing work I just did...AGAIN!!

  7. #27
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    Default What the ech ee double hockey sticks is the difference??

    Here is the GM technical information difference between a 1999 and a 2000 water pump.
    Anyone here have any clue what the real technical difference is?
    Last edited by DieselDobro; 01-18-2019 at 19:29.

  8. #28
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    Quote Originally Posted by DieselDobro View Post
    Here is the GM technical information difference between a 1999 and a 2000 water pump.
    Anyone here have any clue what the real technical difference is?
    The only difference I see is that 19168610 takes a bolt-on fan clutch, whereas 19168609 takes the thread-on fan clutch and comes with a pressed-on belt pulley.

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter

  9. #29
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    Default Both the same..

    Casey, they are both spin on fans...
    I have bought both of them.. one sets on the turd Optimizer I just put in my truck. The other is setting on my desk in my shop. I can't physically work on my truck for a couple more weeks but having looked both of them over and the GEP take off I bought from Peninsular a few years back I can't tell any difference.

    By the way, I'm trying to get the question answered through AC Delco's "customer support". Yeah, hilarious, right?
    That's right they just refer me to call a service facility (GM dealership). What a waste of time, and yes I've done that, too!

  10. #30
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    I still plan to cut each one in half to compare the insides but I'm covered up and haven't had the time yet..
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  11. #31
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    Quote Originally Posted by DieselDobro View Post
    Casey, they are both spin on fans...
    I have bought both of them.. one sets on the turd Optimizer I just put in my truck. The other is setting on my desk in my shop. I can't physically work on my truck for a couple more weeks but having looked both of them over and the GEP take off I bought from Peninsular a few years back I can't tell any difference.

    By the way, I'm trying to get the question answered through AC Delco's "customer support". Yeah, hilarious, right?
    That's right they just refer me to call a service facility (GM dealership). What a waste of time, and yes I've done that, too!
    I'm just basing that off a google search. Pictures of part # 19168610 all come back as a bolt-on fan clutch.

    https://www.google.com/search?q=1916...w=1920&bih=963

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter

  12. #32
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    Quote Originally Posted by DieselDobro View Post
    ...This "balanced" water pump thing seems unsubstantiated when it comes to one spin on fan HO water pump to another....
    Balanced.... ask for the data. Ask for photos of the testing equipment and of the test engine equipped with the flow meters. What engine was used for the test? What engine speed? And on and on... so many questions...

    GM (& AC-Delco) began producing many of their water pumps and many-many other parts in China some years ago. A different part number could be reflective of that. I replaced the water pump on my daughter's Malibu 3 years ago with a new AC-Delco unit. It was made in China... I replaced the water pump on my 2001 GMC Duramax a couple of years ago using a new AC-Delco unit... It too was made in China.

    See: https://www.bing.com/search?q=ac+del...f40bf821fed644

  13. #33
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    AC Delco has no product support that I have shook out of many trees I have shook.

  14. #34
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    Default Aware of Chinese content

    Yes, I did note both the AC Delco 252-776 and the 251-603 pumps were Chinese. Both are HO spin-on fans.

    The 251-603 pump some internet vendors claim is "a balanced pump" and claim the 252-776 is not.
    Having bought both, the 252-776 pump which is actually $100+ cheaper appears to be better quality and even comes with a brass bypass fitting and better quality gasket. There is no visual difference between the two Chinese AC Delco's except I think the Chinese quality of the cheaper pump is better!

    Is there a US made or higher quality alternative? None I'm aware of.
    OEM's move legacy parts to cheaper production. No surprise there.

  15. #35
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    Default Rock Auto purchase

    BTW, both pumps were purchased from Rock Auto who makes no claims whatsoever about "being balanced" on either pump. Sorry vendors, I love Rock Auto and getting as good of parts for a lot less $$.

  16. #36
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    Quote Originally Posted by DieselDobro View Post
    Yes, I did note both the AC Delco 252-776 and the 251-603 pumps were Chinese. ...
    I suspect the different part numbers reflect different manufacturing plants... in China. Different part numbers allow ACD to keep track of who does a better job (parts return percentage, etc.).

  17. #37
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    Default Finally....

    Thats' the first logical answer I've heard on this yet! Thanks, Jim.
    Funny...They are $120 different on RockAuto, even. And I think the cheaper ACD is better looking quality wise!

  18. #38
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    Quote Originally Posted by DieselDobro View Post
    Thats' the first logical answer I've heard on this yet! Thanks, Jim.
    Funny...They are $120 different on RockAuto, even. And I think the cheaper ACD is better looking quality wise!
    The most recent Chinese water pumps do, in fact, look great and of high quality. But it's what we don't know about them that worries me.

    For example, the drive gear on the GM factory Duramax water pump was obviously installed using heat. The flame marks are evident. The hot/cold expansion properties were used to ensure a super tight press fit onto the impeller shaft. The AC-Delco Chinese water pump shows no evidence of a heat application on the drive gear/shaft (the Dmax water pumps are gear driven).

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