OK, when I got '98 T/A all was stock. Water temp. gauge would steady climb in an expected and regular manner until 210. 1 fan would kick on and start running when the gauge would be just above the 2nd mark(no munbers, but halfway between the marked 160 and 210 would be 185) where it reached the factory 187 thermostat setting. If the gauge got to just above the 210 mark, the 2nd fan would kick on and run until the temp was back down to about 200. That was the OEM setting for my car's cooling. Then came the LS1 edit.

A mild, bolt-on modded car only, tune was programmed in which included the electric cooling fans to come on at an earlier temperature with the artificial intelligence of the PCM thinking the car had been fitted with a lower temperature thermostat. However, still the stock thermostat is in car so the fans come on not long after the temperature gauge reads any heat at all, says 165 or so. Now since the stock thermostat doesn't start opening until just after the gauge reaches the 185 mark, no matter when the fans come on or how long they run the motor runs at least 185 degrees. When driving the car, the fans never cut off once I get up to temperature.

There's the background, here's my troubles - My water pump decided to start spewing water under pressure. Whether I have to replace the pump or maybe just some gasket(s) isn't yet known, but what is known is that I'm going to get the correct thermostat in there since I'm going to be all over that area anyway. Why not just go with what the tuner suggested and what matches the tune you ask? Well, I was never told specifics of the tune, just "this will make your car faster and whatever you do don't run less than 93 octane." It did make my car faster, got my speedo to match the new gear, my tranny to shift faster, and my electric cooling fans to run all the time. If I get my thermostat right, then I think my fans will appreciate the break & teamwork of parts working together how they're intended to.

So, judging by above description wouldn't you agree that the correct temperature thermostat would be 160? The aftermarket also sells a 180 thermostat, but that doesn't seem to fit, or does it?

Let me get this straight you have an LS1 Edit tune that changed the fan on/off temps but you still have a stock thermostat. Well that's better than having a 160 stat and stock fan settings.
Essentially I have a similar set up but I have the SLP manual fan switch. When I have the fans on low my temp gauge reads the same as yours did around 185, on High it will read about 170 and stay there. Obviously it does the job and the cars are running cooler and therefore making more power. On a side note the factory gauge is not dead on it reads about 10* cooler than the temp actually is, if you put the car on a Tech II scanner thats what it will read. Just be glad we have Temp gauges that work unlike the latter cars.
Anyway if the car was running well before don't make a drastic change like going to a 160* stat
I think the 180* would be fine, it should provide better cooling and still not take the engine out of regular operating temp. JMO

Depending on where you get the Water pump from it may have a new thermostat already on it,
My GM replacement did.

I agree, I'd just go with a 180 stat. That's what I have in my 99 and even with the mods and tune that I have on it I have no problems with it.

And he's correct some of the replacement water pumps come with a new stat but some of them don't. I think it just all depends on who makes them and where you get them from.

Are you aware that you can modify the stock t'stat by adding a brass ferrule, and adjust it to whatever temperature you want? Its covered in a sidebar in the Chris Endres book on modifying the LS1 engine.

Yeah I think I've read something before about doing that to a 'stat, but I just bought another anyway. Everything is getting old and worn on this car, so when time comes, I've been going newer/stronger/better on most all parts that have trouble or completely break.

Anyway, I went with the 160 Hypertech thermostat, along with a new water pump(not cheap on LS1s by any means), fresh new A/C compressor belt, and pulled the radiator while I was there to get the debris out that was stuck between it and the A/C condensor.

The pump may be a lot more $ than your average water pump, but the install is very easy and is no more than a 2 hour job. Now the car runs right where the fans timing suggest it should, just barely north of 160 degrees. I still have good heat/defrost on these cold mornings and the fans don't have to run all the time to try and compensate for a 'stat that doesn't match their settings.

Good to hear
Yeah those water pumps aren't cheap are they !
Did mine 2 years ago and almost blew a nut over the cost.
Alternators and Starters aren't cheap either from what I hear.

Thanks!

Did a starter once too, an AutoZone one, but forgot $ because returned with refund. Come to find out, wasn't the starter, it was the ignition switch harness on the column, but I swapped the starter on a gravel driveway with stacked logs for a jackstand before I found out that wasn't the problem

Alternators - I hear the hot item for low cash is a used piece of a 6.0L truck motor... even more juice.

The water pump I did was a AutoZone piece too, $140ish, but I priced OE from dealership... $320 no 'stat, $360 with stat! I usually by OE, especially since I get big discount, but didn't even consider discount this time, especially after sales clerk was a total donkey's behind. AZ warranty lifetime too, OE 12 months. I just kept my core and will rebuild me one and have it ready to go or sell at a moments notice. Might even polish the housing and make it a show quality WP !!!

When I did mine 2 yrs ago GM ws the only place to get it.
AZ, Murray's and Pepboy's didn't carry them yet.
I had a buddy that worked at a Chevy Dealer and he set me up with one for $190 w/Thermostat.

Good to hear that you've got your car fixed and back up and running.

when my WP goes I'm going electric

not much more $$ and frees up HP

Just be careful with the electric WP Charlie. Lots of them out there have a useage time limit on them, which from what I've seen is approximately 5000 hours. So I'd check them out fully before you do get one.

thanks

of course i'll check

5k hours isnt too bad for me - I drive the Z about 4 hours a week which would be about 3 1/2 years

hummmm

and I have to back out jail time so it may be even longer

You're welcome. 3 1/2 years isn't bad for getting that many hours but I just wanted to be sure you were aware of those time limits.