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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #1
Hey guys, as always I appreciate all your input. Well, I'm getting ready to purchase the AC Delco 251-603 water pump, Hayden 2886 fan clutch, and the Duramax 21" fan for my 6.5l build. I have 2 questions that I'm unclear of at the moment.
#1) After reading Bill Heaths pdf on this subject, he hails this IS the best setup for the 6.5, along with the single stat crossover, which IS what I have from the factory in 93. I wish to keep the single stat crossover. Since I want the full advantage of this setup, do I need to block off, or do any type of bypass restrictions, that some talk about to get the full 50/50 balance of cooling?
#2) The AC Delco is a pricey pump. Is GMB, or Gates, just as good, or just pay the extra for the real deal? I have no problem spending the extra cash, if its money well spent.
I believe in doing the right thing once, and we all know....
You get what you pay for!
Thanks guys馃憤
 

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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #2
Just to add, after reading Bill Heaths file on this subject, I'm less to believe that with a single stat crossover, I need nothing, and should be good to go. It is the dual stat crossovers that supposedly need a bypass restriction.
I'm I correct on this assumption?
 

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You are correct, the single thermostat closes off the bypass when it opens.
 

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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #4
Thanks appreciate it!
Any recommendations on the pump brand?
 

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You could consider this -
 

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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #6
Its definitely a bit cheaper, so I WILL consider it an option.
Thanks again.
If anyone else can maybe give their input on these brand of pumps, I would be extremely appreciative.
I'll leave my options open for now, and see what the consensus is from all the great people on this site 馃憤
 

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My truck is a '93 and I'm using the bigger fan, later model higher flow water pump and the dual thermostat crossover. I noticed after doing it that my temp. gauge did not have the wider swings when the dual thermostats opened versus the single stat. Very noticeable. If Bill Heath would publish some numbers from his research into his opinion that the single stat is the best, I'd sure like to see them. Just my .02, but I think he's dead wrong. GM went to the trouble/expense of dual stats for a good reason, I believe.
 
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Ahhh. The old single vs dual debate. I like dual. Cuz the heater works better and coolant temps are more stable. Gets below 0 where I live, Even not plugged in. My truck warms up fast and is toasty warm on the coldest days.
Some people say single cools better. I have never had a single cooling issue with dual stats.
I figgure GM went with dual stats and a HO water pump for a good reason. I have never had any reason to change the set up.
 
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went with a Flowkooler from Leroys and a Duramax fan, and 190 A/C Delco T-stat. Overheating problem went away. ( Cleaned the rad, also)
 
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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #10
After some extensive research I've found the flowkooler pumps are just GMB pumps, with fancy CNC machined impellers. The reviews I've read have not impressed me either, some I think I'll avoid the flowkooler pump, and run with the much better proven, but pricey AC Delco unit.
That's my 2 cents though, on that. I hope you guys fair well with the flowkoolers. I figure that a $72 GMB pump probably has cheap chinese bearings and seals in them, to keep the cost low, as that's the area most parts fail at, when they are priced cheap. I'm in this for not only performance, but reliability, and longevity, and from my research, the flowkooler pumps seem to work well, they just dont last as long as one would expect them to?...
 

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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #11
Tommygunner, I have 4 documents that I will post here, that will answer all your unknowns about that data by Bill Heaths testing on the cooling system, and t stat crossovers. I dont doubt your experiences, but there are many variables as to why you thought differently. The size of t stat used, using the proper restriction, the cleanliness of your radiator inside and out, etc. I know from "my" experience, with my stock 93 cooling setup, my temp gauge never fluctuated much, and never moved off of 200, all day long, damn near regardless of my situation....but that's only "my" experience.
I really never had cooling issues, but since the motor is out, and I restoring the whole truck, I just want to have the best combinations available at this time. Therefore I'm going with the single stat crossover, as Bill Heath recommends.
Here are his 4 page files below. Thanks all.
639312

639313


639315

639316
 

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Thanks for posting that, gman. Heath may be right about the single/dual thermostat issue. I've had 0 problems with my dual stats and higher flow pump/big fan though.
 
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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #13
You're welcome 56pan.
I know we all have our opinions, and IF my truck had the dual stat crossover, I'd keep it and just do the restriction. Since mine is already a single, I'm just gonna stay with it. Sometimes the crossovers can be pricey too, so I'm just doing the best I can to save money here and there, as building an entire truck adds up quick, so $100 here or there is somewhere else I can spend the cash!! 馃憤 There are more ways to skin a cat, and as long as we all are happy with our trucks, then all is good right?!
 

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Tommygunner, I have 4 documents that I will post here, that will answer all your unknowns about that data by Bill Heaths testing on the cooling system, and t stat crossovers. I dont doubt your experiences, but there are many variables as to why you thought differently. The size of t stat used, using the proper restriction, the cleanliness of your radiator inside and out, etc. I know from "my" experience, with my stock 93 cooling setup, my temp gauge never fluctuated much, and never moved off of 200, all day long, damn near regardless of my situation....but that's only "my" experience.
I really never had cooling issues, but since the motor is out, and I restoring the whole truck, I just want to have the best combinations available at this time. Therefore I'm going with the single stat crossover, as Bill Heath recommends.
Here are his 4 page files below. Thanks all. View attachment 639312
View attachment 639313

View attachment 639315
View attachment 639316
While Bill did know his stuff, he over charged for his products.
Case in point this "Cooling upgrade"

All BIll did was install an OEM HD water pump, HD fan clutch, Dmax fan.
To improve the flow he took a $20 brass plug, put it in a Lathe, and made a bypass restrictor fitting, installed it into the water pump crossover fitting, and charged a stupid amount of money.
If you look on Heath's site today they want 500 bucks.

If you take this link: 6.5 Cooling system Parts and pieces for upgrade and individually source each part online/locally, you can spend way less on those parts.
You can make your own Bypass restrictor to install in the waterpump or find one online cheaper..
 

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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #15
I totally 100% agree Okdually. I can buy all these separately for well less than $300, and get GM Delco, and Hayden parts. Sadly I can say the exact same thing about most Diesel retailers, and one that takes the same stuff and Mark's it up 50%-100% is Leroy Diesel. He has good ideas, a parts, but I hate to say it... Its a rip off. Sorry.
 

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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #16
Heres a question if any of you can answer this one, cause it seems like alot have mixed theories.....
On the GM waterpump #88894035. This pump cross references to the
AC Delco line #251-603....most expensive one.
Theres also an AC Delco professional line.....#252-776 about $75 cheaper.
Then theres probably an AC Delco Advantage line # ,but that's not even a thought, because it's the cheapest line of parts they make.
Of those 2 options, which IS THE BEST?
And IS the AC Delco line by itself the SAME as the OEM? I would assume so, because of the cost difference, but hopefully someone else can elaborate on this!! Thanks all馃憤
 

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Heres a question if any of you can answer this one, cause it seems like alot have mixed theories.....
On the GM waterpump #88894035. This pump cross references to the
AC Delco line #251-603....most expensive one.
Theres also an AC Delco professional line.....#252-776 about $75 cheaper.
Then theres probably an AC Delco Advantage line # ,but that's not even a thought, because it's the cheapest line of parts they make.
Of those 2 options, which IS THE BEST?
And IS the AC Delco line by itself the SAME as the OEM? I would assume so, because of the cost difference, but hopefully someone else can elaborate on this!! Thanks all馃憤
AC/Delco is the OEM replacement the "professional" line is usually the, imported from China, (approved AC/Delco).
Part tiers are used as a sales gimmick to generate profit.
You can use it but may have
Have you looked on the rockauto site? they show an AC/Delco for your truck.
You can also try our supporting vendors
Unique Diesel Welcome to Unique Diesel - GM Truck - High Quality 6.2 6.5 Parts Source
Kennedy Diesel Kennedy Diesel
 
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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #18
Thanks again Okdually. You are right. I already got some parts from Rockauto that were Genuine GM parts. I guess the boxing can be confusing. It seems if they are Genuine GM OR AC Delco, they are GM Original Equipment. Anything else like the Professional, or Advantage line, are just upper and lower level product lines. I'm definitely sticking with the OEM part here. May be a little more, but I'm sure it will last. I'll check out the other vendors as well. Kennedy Diesel has always had some good stuff for our 6.5s too!馃憤
 

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1993 GMC K3500 Sierra SLE Ext. Cab Dually. 6.5l diesel turbo, NV4500 5-speed.
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Discussion Starter #19
Any opinions out there on the best overall Hayden fan clutch?
I can't really find the specs needed to decide which is the better option, the 2840 or the 2886?
 

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Any opinions out there on the best overall Hayden fan clutch?
I can't really find the specs needed to decide which is the better option, the 2840 or the 2886?
According to the cooling upgrade link 6.5 Cooling system Parts and pieces for upgrade the two recommended are:
Hayden severe duty:# 2839 (stock engagement) bolt on
Haydon Severe Duty spin on Fan clutch: #2840 (stock engagement)
 
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