AWD 99 2 Door Tahoe Build

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Jnunez74

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I think you meant outlet ... reducing the outlet diameter will reduce the flow. I don't think it should ever be bigger than the inlet or you will lose pressure in the block.

Do you have the stock outlet and pump? I would try putting those on.

You could also experiment with the pulleys. You could put a larger pulley on the water pump or a smaller one on the crank to slow the pump down.

It's hard to diagnose and fix over the internet, for example you could have a head gasket leaking exhaust into the coolant.
Well, I did it all, reduced water neck to 1 1/4, that didn’t help. Swapped water pumps to a stock flow one, and that didn’t help anything but reduce the pressure. Did more coolant and that was a bust as well. Stays at 185 idling, soon as I try to drive it skyrockets to 235 and keeps climbing. Really at a loss, tryna see if I can get a blade for the fans with a higher pitch but beyond that I have no clue
 

0xDEADBEEF

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Well, I did it all, reduced water neck to 1 1/4, that didn’t help. Swapped water pumps to a stock flow one, and that didn’t help anything but reduce the pressure. Did more coolant and that was a bust as well. Stays at 185 idling, soon as I try to drive it skyrockets to 235 and keeps climbing. Really at a loss, tryna see if I can get a blade for the fans with a higher pitch but beyond that I have no clue

What shroud are you using?
 

Jnunez74

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Holy cow, awesome job, the time and work involved? I have my old stock 94' at the shop now, getting some paint work done , and would love to just drop a 5.3 in there, but being a farm cruiser and toy, I'll have to keep the 5.7 a while. Good luck on yours!
I’m well over 200 hours in it at this point, but it has been worth every second with the experience gained! The ls swap would probably go a lot smoother than this one has, best of luck with it either way, the 5.7 will keep on keeping on if you take care of it
 

GoToGuy

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Are you sure you're thermostat is operating properly?
A super high performance engine generating a tremendous amount of heat would need higher flow to draw away excessive heat.
Don't confuse temperature and radiator cooling system internal pressure.
Increasing the internal cooling system pressure results in increasing the temp at which coolant boils.
What thermostat temp are you using. Thermostat is correct fit installed with correct gasket or "O" ring style. I found once wrong gasket installation causing overtemp. The pressure contained in the cooling system is limited to what the cap is rated. Expansion recovery tank retains some then returns to system when pressure reduces. You said it has high pressure? How do you know? Do you have a pressure indicator or pressure gauge on cooling system? if the cap operates as designed the max pressure is never greater than the caps rating. What is your systems rating, GM truck, radiator manufacturer? Have you inspected the cap? Proper fit? Cap seals whole no cracks? Are you sure the aftermarket radiator and cap are compatible? Tested cap? Holds and releases pressure at rating?
And your sure there are no obstructions in the radiator, proper cross flow.
Is your radiator the same size, capacity as a big block, tow package , K2500, suburban would have? As a equivalent example.
The 1/4 " difference is not a factor in your build. The perceived reduction in volume is negligible, your flow is no where near maximum velocity for the diameter.
What clearance did you use for your extra fluid coolers in front radiators/ ac condenser? From what you've described I've tried to cover some possibilities.
Good luck !
 

Jnunez74

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What shroud are you using?
one that I fabbed, these fans aren’t pulling like they are supposed to, even off the shroud the are lackluster, jegs basically told me to just send them back and get a different set. Incredibly frustrating experience with them. The blades have pushed on one side and puller on the other and they weren’t aware of this. The truck guy had mentioned that a different kit required reversed polarity so I went ahead and flopped it on this one and now she exists happily at 185
 

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Jnunez74

OBS Enthusiast
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Are you sure you're thermostat is operating properly?
A super high performance engine generating a tremendous amount of heat would need higher flow to draw away excessive heat.
Don't confuse temperature and radiator cooling system internal pressure.
Increasing the internal cooling system pressure results in increasing the temp at which coolant boils.
What thermostat temp are you using. Thermostat is correct fit installed with correct gasket or "O" ring style. I found once wrong gasket installation causing overtemp. The pressure contained in the cooling system is limited to what the cap is rated. Expansion recovery tank retains some then returns to system when pressure reduces. You said it has high pressure? How do you know? Do you have a pressure indicator or pressure gauge on cooling system? if the cap operates as designed the max pressure is never greater than the caps rating. What is your systems rating, GM truck, radiator manufacturer? Have you inspected the cap? Proper fit? Cap seals whole no cracks? Are you sure the aftermarket radiator and cap are compatible? Tested cap? Holds and releases pressure at rating?
And your sure there are no obstructions in the radiator, proper cross flow.
Is your radiator the same size, capacity as a big block, tow package , K2500, suburban would have? As a equivalent example.
The 1/4 " difference is not a factor in your build. The perceived reduction in volume is negligible, your flow is no where near maximum velocity for the diameter.
What clearance did you use for your extra fluid coolers in front radiators/ ac condenser? From what you've described I've tried to cover some possibilities.
Good luck !
I used a cold case radiator for a k2500, the polarity on the fans were wrong from the factory… I thought to myself, “wouldn’t it be stupid if swapping the polarity made them behave properly” (the blade themselves indicate that there is a push and pull side). And of course it was the thing that I thought would be a bust that solved the issue. As for the cap, I’m not entirely sure on what the rated pressure is, it blew off excess pressure around 225 F but I’m not sure what kind of pressure the system was under at that point. Since swapping to a 350 neck, a LS upper hose and the low flow pump I no longer fear believe there is an excess of pressure. I took it out for about an hour today and it stayed at 185, ran it in 1st for about half the time at 2500 rpm and it didn’t touch 190 a single time. That was with one fan at 185 and the other set to 195 through the Pro-flow. As for the rad, condenser and trans coolers they all have atleast an inch of spacing between them so they shouldn’t be choking one another.

I will say that this has definitely humbled me a good bit I shouldn’t have taken the work of the manual on the installation and flipped the polarity sooner.

Now the trans stays at 130 as well so it would appear as if these issues are resolved. I appreciate all of the support and suggestions and I am going to go through it all again tomorrow and make sure it is optimized
 

0xDEADBEEF

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one that I fabbed, these fans aren’t pulling like they are supposed to, even off the shroud the are lackluster, jegs basically told me to just send them back and get a different set. Incredibly frustrating experience with them. The blades have pushed on one side and puller on the other and they weren’t aware of this. The truck guy had mentioned that a different kit required reversed polarity so I went ahead and flopped it on this one and now she exists happily at 185

I've got a single Black Magic fan on my build and it moves some serious air for its size. I think it's rated for 3000 CFM. You can feel it in front of the truck, no need for the paper towel test. 2 of them would really move air.

I have my fan programmed to come on at 200 and off at 195 and it only takes a minute or two to do it. I'll be switching to a colder thermostat soon and reprogram it.
 
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