T3 water line thread/pitch

FWIW I've been running a "water cooled" T3 with no water lines for like 3 years with no ill effects. Just gotta give it a minute to cool down after running hard.

Yeh, I know its common to delete the water lines, but our situation is a bit different than even an aggressively driven street/strip car. I figure anything I can do to combat heat (within the rules) will be beneficial.

You must run coolant lines if you want to turbo last. I have friends running in Chump car with a Volvo 240 wagon 2.3L turbo running a Z31 turbo. They fried 3 Z31 turbos at Road Atlanta from not running the water lines. After they had the turbos rebuilt they ran the coolant lines and the same turbo has lasted another round of Road Atlanta, Sebring, and Daytona.

-8 lines seem about the stock size as the stock hoses.

I'm using 3/8 tube X 3/8 npt stainless swagelok fittings at the turbo and .375(3/8) OD X .319 ID stainless tubing plumbed up to the stock coolant pipes, bypassing the TB.

I'd recommend using stainless as I've personally had aluminum Earls AN fittings develop pinhole leaks in their tubing elbows.

Thanks for the replies guys.

Egg, thats confirming what I kind of expected. I've only got the one so I need it to last, although I am keeping my eyes out for a spare. I was leaning towards -8.

ZKarma, but what male fitting did you use for the turbo? the stock banjo? My calipers are measuring ~0.63ish so I'm guessing its M16, but was hoping someone has already been down this path. I haven't looked at the swagelok fittings but was considering the forged AN fittings for strength/durability at the turbo.

I used 3/8 male npt to 3/8 tube at the turbo.
The stock banjo bolt is a machine thread, but it's close enough to 3/8npt that i tapped it for that.
I had access to a tube bender and a lot of scrap SS tubing at a previous employer, so that's what i used. No leaks for ~10 years now.

I previously used a 3/8 male npt to -8AN to Earls elbows like this. Then to some aeroquip hose.
The arrow points to where i experienced the leak. I'm guessing the quality of my coolant made easy work of getting past their anodizing to attack
the aluminum at a point where it sees a fair amount of velocity. It basically abraded it from the inside out.

I deleted the water lines for over 10years with no problems just let it cool down for a few minutes.

Guys, you are missing the point here that this is a race car. Not a street car. Race car needs the coolant lines to keep the center section oil temp in check.

With a double row rad? My temps go over middle with a single row at heavy load in hot days

Yes, this is a purpose built endurance racer. 40-130mph pulls for 10-24hrs straight with 5min pit stops every 2hrs. Outside temps will range from 40-100+°F. It will be tortured. Running w/o the lines isn't really an option for me.

I really don't want to retap the threads. I'm getting .640" on my calipers to the inside threads so its not M16. 11/16" maybe? Nobody knows, huh? Anyone have a set of OE lines laying around?

Finally found it, M18. Interesting enough, the same thread as a standard o2 sensor.