6.5 water pumps

[Kennedy]

I would really like to know if there is a true factual basis for why the 4 stud style water pump flows with a supposed huge flow bias where the thread on style does not. I would think that a picture should show immediate differences if there were any. There are 6.5 vendors out there that make statements about the 6.5L cooling system that they cannot prove. They may talk about testing, but provide absolutely no factual data or proof of how the tests were performed etc. They just make bold statements.

[Kennedy]

In the case of the 6.5 water pump I would think that the simplest place to start is by building a rig where the water pump moves water from the lower rad hose through equal sized pipes with flow meters first in order to see if the supposed imbalance is due to pump design or not. My speculation is that the results would show little to no difference.

From there other tests could probably be performed, but by my way of thinking there's just no way that you can take a centrifugal pump and bias the flow or pressure to one side or the other without a major (and obvious) change in casting passages and even then...

[More Power]

I would really like to know if there is a true factual basis for why the 4 stud style water pump flows with a supposed huge flow bias where the thread on style does not.

I'd like to know that too.

Logically... If I were selling 6.5 cooling widgets, and made some claim, I'd have the data - verifiable - provable/reproducible data for which the claim is based. I'd also have a series of images that show that we actually did the test. Doing a quality data collection project is a lot of work. If you're "in the business", you would not waste that effort by not collecting images and data.

Our own Pull-Off Series was done in front of everyone interested in GM diesel performance. Some got to ride along, use their own stopwatches and even look over the shoulder of the driver to record speed and engine data. We also did an instrumented fuel economy data analysis where we measured fuel use with a 6.5L diesel on an engine dyno at various engine speeds and loading. We did that test in front of dozens of you guys.

It's amazing that some 6.5L diesel owners don't apply logic when looking at ad claims.

Edit: There are a couple other topic threads in our 6.2L/6.5L Tech forum related to "being curious" about ad claims:
https://www.thedieselpageforums.com/...splay.php?f=22

[sctrailrider]

The only difference I "saw" was a larger impeller than the early 4 bolts, but the later 4 bolts "should" have a HO in the casting, these are said to be the better flowing 4 bolt units.



With the Humvee fan system I am using I will be staying with the 4 bolt version.



Nice work John glad to see this kit come back !

[JeepSJ]

What do you all think about the "restrictor in the bypass" on the HO pump / dual t-stat setups?

[More Power]

As luck would have it, I have both a 1997 "HO" 130-gpm 4-bolt-fan water pump and a newer screw-on-fan 130-gpm high output water pump for the 6.5 sitting on my work bench.

The impellers are exactly same diameter, thickness and appearance. The coolant flow passages, dimensions, appearance and every other detail appear exactly the same between the two pumps.

I'll have close-up pics sometime this weekend, that I'll post to this thread.

[sctrailrider]

What do you all think about the "restrictor in the bypass" on the HO pump / dual t-stat setups?

Myself I think it's a bad idea and giving a false sense that things are running cooler when the head is actually running hotter.



Why would restricting water flow anywhere in the system be a good idea? The block off type were taken out of use for a reason, I don't know for sure but I would bet it was to incress flow through the system..

[ronniejoe]

What do you all think about the "restrictor in the bypass" on the HO pump / dual t-stat setups?

https://www.thedieselpageforums.com/...ad.php?t=45811

This thread discusses this topic.

[ronniejoe]

I would really like to know if there is a true factual basis for why the 4 stud style water pump flows with a supposed huge flow bias where the thread on style does not.

I think it is pretty clear that this is a myth.