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88894035?

I checked rockauto, this is the water pump for 2000 model year. But they also shows the same year with earlier model pump.

However, the pump is important but the fact that Heath puts a restrictor in his system to balance the flow is also important. I am not sure if that restrictor is part of the t-stat or something separate. Plus the HD fan and the HD clutch.

No I don't have any experience with it.
 
I may be wrong but I think the restrictor is the thermostat and the key is the pump. The problem is the upgrade of the pump means a new screw on clutch for those of us who have bolt ons. The cost grows exponentially.....
The ACDelco pump 251-603 may (or not) be matched by the Alliant Power pump AP63561.
 
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Seems like I read a blurb a good while back that near the end of the 6.5 GM production they were gearing up for the new fan for the Duramax and went ahead and installed it on late 6.5's. Or were something like they were going to make it interchangeable or something like that. Is this the pump that was able to do this? IIRC Cheverolet went to the Duramax almost whole heartedly but didn't GMC offer both for a while or was 2nd to change over ????
 
And just to muddy the waters some, what is an ACDelco 252776? Rock Auto is listing different pumps for 2000 and 2001 vehicles. They are both down to around $150 now.
 
I'm right in the middle of installing the Heath Cooling upgrade. Hard to see the differences between the pumps that would result in a higer flow rate. It looks as though the vanes on backside are a bit longer on the HO:

WPI-1-1.jpg


There is definitely a difference between the stock '97 and Heath's Orifice:

Or-1.jpg
 
guybb3 said:
Big T, if you wouldn't mind, can you use a drill bit or equivalent and give the size of the orifice in the new water pump?
Click to expand...

It's slightly smaller than a #2 pencil bigger than a 1/4" drill bit. I'm a bit under the weather today (cold/flu/achy), so I'll go out and officially size it tomorrow. My remaining parts (timing chain, etc) come sometime tomorrow, so the work begins. Need to have it running on Saturday.
 
Very interesting thread.

I know its an old 6.2 but the cooling systems must be made alot better as towing, flat out in 2nd or 3rd going up steep hills, my temps don't get that high, :thumbsup: Maybe the turbo will change that?

The only mod is a recored stock rad thats 4 rows instead of 2, and a high flow stock stat.
 
This thread actually got me out from in front of my computer and out in the -20 temps to pop the hood on my truck and look at how everything was routed. Never paid any attention before and when I saw where the orifice was I thought that outlet went straight to the heater like on the older trucks. Learn something new every day.
 
turbovanman said:
Very interesting thread.

I know its an old 6.2 but the cooling systems must be made alot better as towing, flat out in 2nd or 3rd going up steep hills, my temps don't get that high, :thumbsup: Maybe the turbo will change that?

The only mod is a recored stock rad thats 4 rows instead of 2, and a high flow stock stat.
Click to expand...
The 6.2s were naturally aspirated, Bigger copper rads and much better airflow from body design.
As you all know from my many many inputs on cooling and my overheating and quest to solve same I looked into all this. Buddy is correct. The # Bill gives in the article is for the 2000 water pump however I had a 2000 with that WP factory and the cooling system didn't work anybetter than my 95 with Bill's upgrade. They were about equal. What DID make a big difference on the 2000 was keeping the stock fan but upgrading the clutch to the Hayden Severe duty. I think personlly it worked better than the dmax fan but I sold both trucks before I had a chance to switch them and gather data. I personally still stand by my opinion thaat the biggest problem with these trucks is lack of airflow. I know a contractor who has two trucks, both with 6.5s. One is a 94 with stock WP and he towed heavy equipment without any issue or ever running hot...Why ?? NO A/C condensor. ONe of the experiments I never got to do with my Tahoe was to remove theA/C condesor and go for a nice hot tow(not to be confused with a Hot Karl...):h )
. Does the better WP and better fan in the Heath upgrade help ?? IMHO yes it squeezes every availible bit of cooling from the 6.5 buit the real problem I think is lack of airflow and in extreme conditions(guys running more fuel and mods) lack of an IC .
 
To back up the uneven flow claim... The 1995 gassers had a TSB for a updated water pump. The update was for even flow to the block. My 350 would boil over without the temp gauge moving. Weirdest thing I have ever seen as the pump passed the squeeze the upper hose test for 'flow'.

Maybe this uneven flow was a 1995 problem or covered many years. The test vehicle was also a 1995 6.5TD for the article.
 
ak diesel driver said:
This thread actually got me out from in front of my computer and out in the -20 temps to pop the hood on my truck and look at how everything was routed. Never paid any attention before and when I saw where the orifice was I thought that outlet went straight to the heater like on the older trucks. Learn something new every day.
Click to expand...
l
I was in the same boat.....errr pump, though the temps here are reaching 70 during the day. I was scratching my head as where this so-called orifice could be on the pump, looking at where pump pulls coolant from the block. Not there as it's the same as the '97. Then I see threaded in fitting and noticed the difference in size (see pic) and that had to be it. I take it this is the bypass? Does this allow bypass before the thermostats are open? Maybe someone here can explain the coolant flow so that I/we can understand what this orifice is doing?
 
WarWagon said:
To back up the uneven flow claim... The 1995 gassers had a TSB for a updated water pump. The update was for even flow to the block. My 350 would boil over without the temp gauge moving. Weirdest thing I have ever seen as the pump passed the squeeze the upper hose test for 'flow'.

Maybe this uneven flow was a 1995 problem or covered many years. The test vehicle was also a 1995 6.5TD for the article.
Click to expand...

Uneven flow is an issue with these. Heath 1st gen cooling upgrade IIRC was a crossover on the back of the heads or someting like that. I'm sure TD will chime in, IIRC he had that mod or still does.
 
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