I guess it's time to order a M11 x 1.5 thread chaser. Thanks very much everybody.
I'll let you know how I make out (when it's not -4 degrees out).

 

Do it the first time and sleep at night.
The head bolts should be new when you do the job because they are "torque turned" and do set after they are installed.
When I did engines like this I found out if I turned the first one to spec/method and went back with just a torque wrench and found the value at which the wrench clicked at I could torque the rest without "torque turn".
I did this not only with head bolts but the conntecting rods and main caps.
I'm called Cat Man because for 32 years I worked at a Caterpillar dealer and built/repaired many a diesel engine. 3516's were the ones I liked to do and they were 263 cubic inch per cylinder.
I don't believe everything an engineer thinks is right/correct and have proven some of them wrong on the projects I was allowed to work on with them.
I always say "Someday's your the bug, someday's your the windshield."
Did have my own repair shop fixing car's also.
OK it's off my chest let's move on.

 

First time torque to 22 lb ft then 155 degrees. They say to use new bolts, most people don't. GM says to use new bolts almost everywhere, I'm not sure where the CYA ends.

 

donbrew
I have the new bolts and I have a torque gauge. I get out of work in a couple of hours
and can't wait to see if the M12 x 1.75 thread chaser fits the #3 holes from your drawing.
I've already ordered a M11 x 1.5 chaser. After this head is on I have a 1999 Cadillac Eldorado
I have to do the heads on (do those guys have an info club too). I got the HHR for $900 but it wouldn't
pass emissions. One of the exhaust valves on the #3 cylinder was dinged up. I drove it for 7 months before
the sticker ran out(Massachusetts). It's a great little car. I want to keep it for at least another 150k miles.
I can't believe how fast answers to my question came in. I've been to the site several times before
but never signed up. I think this is going to avoid a lot of aggravation. Thanks again to everyone who replied.

 

Here is the problems with Northstar.

https://itstillruns.com/cadillac-nor...s-6637955.html

 

Bought a 97 STS in 07 from a guy with a blown head gasket for 7500. Got a hold of a GM test engine, did the timesert deal to the block and used ARP head studs. Never had another problem. Also replaced the lockup torque converter with a 3K and better internal clutch. Really woke that car up. I don't believe head gaskets are a problem with the newer ones, guess I'll find out since I have a 2006 STS V with a supercharged 4.4 Northstar.

 

The ARP head studs are best for aluminum engines, the TTY bolts are fine for production, but if you spent time, money and effort to rebuild your Ecotec, I recommend them.
I never had a problem in my BBC or SBC engines with aluminium heads.
Henry must of had confidence in studs for the flatheads back in the day!

 

Head studs are best all around, that's why Henry used them in his cast iron engines also.