Broken Exhaust Manifold Stud

[nyvoyager]

I am sorting out a new to me late model A4.
The engine had been sitting in a garage for years, likely around 7 or 8 years.
While still sitting on a pallet under the boat , I pressure tested the block - it checked out.
Drained and replaced the oil. Spun it with a hand crank. All good.
Cranked it with no spark to get oil up and around.
Compression check revealed a stuck valve in #1 cylinder. Some MMO and a few more cranks and all well - compression on all 4 cylinders is spec.

Wired it up and it started on the 2nd crank.
Let it run for a minute and it sounds good with no smoke.
**** I did this with no water and pulled the impellor. I just wanted to get it started.

Fast forward:
I had to move the boat to another yard so the engine is sitting on the cabin sole knowing I have a few things to sort out and parts to switch over.
I have basically stripped all the accessory parts off including the exhaust manifold.
It turns out the center stud is broken and i don't believe it was by me. I used very little force to remove the bolts. The center stud just spun out.
Unfortunately I didn't take a photo of the threads but they look clean and in near new condition.
My thoughts are to pick up a reverse drill bit and easy-out
My questions:
What size bit and easy-out should i use?
Do i need to put sealant on the threads when reinstalling? - the threads are good.
what is the rust on this one port?

If this helps: the reason I pulled the manifold i because the exhaust flange bolt was snapped off. The other appears rusted in fairly well. The manifold itself appears in good condition but I have a new MMI manifold sitting here and will install it.
The next step will be to try and figure out why there is no thermostat in the housing
Thanks all.

[Al Schober]

Sorry, I'm confused.
Photo shows the manifold studs in place. You say the center stud is broken and that it just spun out? Why do you need a 'reverse drill bit' if the stud is out and the threads look good? DO NOT buy/use EZouts! When one of those breaks off in a drilled hole, you're out of luck - no more options. Perhaps we need a current photo? If the stud is out, you can just reinstall it. If it's broken, you need a new stud (our Host sells them).
Those studs keep coolant in the block and need sealant. I use JBWeld.
Thermostat may have been removed to reduce engine temperature. Leave it out unless you decide later to install it. I ran without one for 15 years!

[nyvoyager]

Sorry for the confusion
The stud is broken. There is about 3/16" threaded into the block
I need to extract the remaining bit and install a new stud
If not an easy-out - then what extractor?

[Al Schober]

I'd recommend a left hand drill bit, about 1/4 diameter for the 3/8" stud. I bought an assortment of these from mcmaster.com - as I recall, they're even available in cobalt alloy.
I've got several metal cabinets, each with about 2 dozen pull-out plastic drawers. One drawer is just cobalt drills. Left and right are all mixed in, which gets interesting sometimes.
edit: PM me with your address, I'll send you one.

[nyvoyager]

Thanks Al. While I appreciate your generosity, I don't want you to go out of your way.
In return I have a bunch of parts, early and late model.
Respond to my PM with what you need
and I'll see what I have.

[Don Moyer]

nyvoyager,

In later late model engines we have seen quite a few cases where what you think is a piece of stud broken off in a manifold stud hole is really nothing more than calcified residue remaining from the end of the stud. One indication of this possibility is if the end of the stud is sort of rounded off instead of showing a clean break. A buildup of calcified crud/residue can usually be cleaned out using a smallish screwdriver (sharpening the tip helps) by gently tapping and turning the blade - sort of like the technique in using a "star" drill in concrete. After cleaning out most of the calcified crud you can use a coarse threaded tap to finish cleaning up the threads. Don