spare time toys

At one point in this engines life someone broke off both rear exhaust studs. Im trying to find someone who has drilled them for an EZ out before. Just want to get info before I start.

UKKid35

Not done exhaust studs, but I think the key is to drill the hole dead centre, and accurately inline with the stud. Since you have the engine out, it should be possible to avoid using a hand held drill.

Actually I'd probably drill the stud out and then re-tap, rather than risk an EZ breaking, because that would be awkward.

jaycm

use left handed drill bits. i use a bunch of penetrating oil and let it sit for a while. if the engine is out, turn the engine so that the oil will run down into the threads. clean the area around the broken stud and use some silicone to build a "dam", pour it full of penetrating oil, and let it sit overnight. sometimes the stud will actually loosen itself up and twist out by itself using the left handed bits. use a center punch to start the bit. re tap the holes and be sure to use some type of anti-sieze lubricant when re installing bolts.

Gregg K

I've done a number of them. I think you'll dislike my method. I start with a centerpunch. Then I work my way up from a small drill, to the largest size I can that doesn't start drilling the block. At some point, the stud threads will come out with a dentists pick. I only do this because once an easyout breaks, you've got a new world of problem to deal with.
Having said that, I've heard the left handed drill bit really does the job. I've never tried it though.

One suggestion is to use a propane flame to gently warm up the area if you intent on backing out the broken stud. Good luck helps too.

928FIXER

Lets see...engines out so I would start to by heating broken stud with oxy/aceetylene tourch until broken stud is cherry hot and soak with nut buster until cool.Then onto center punch(and in the center is very important) ,1/8 inch starter bit new out of box,then onto a left hand drill set and if your lucky it will come right out as you increase to a larger diameter bit.If not drill until its very close to threads and pick it out with small seal pick.Chase with a tap nice and slow.Install new stud.

V-Fib

When I had my heads (4.7L) reworked, The machine shop fixed a couple of stud holes that had been butchered to the point where they were drilled into the water passages. Imagine my surprise when I removed the oversized studs and had coolant running everywhere. They welded them and redrilled/tapped them. I would suggest having a good machine shop do it for you. More $$$ up front, but if you screw them up, they will charge even more to fix it correctly. JMHO

Sean79 5spd

Anthony, go with the machine shop. I broke off one of the bolts that holds the thermostat housing to one head. I drilled it and used an EZ out. The EX out broke. Now I am at the machine shop anyway.
Good machine shops are much better equipped. I am also having them plane the heads, about 5 thou.

Sean

GlenL

Machine shop.

I drilled mine from below with the engine in. Then busted the EZ Out. Then drilled that. Off-center, of course. Finally made it work. The Al is very soft compared to the old, hardened stud.

The shop charged $1/min to fix it. I had pulled the heads to do the gasket. Worth every 1.66c/m!

Ron_H

Where are you? If you are in the San Francisco Bay Area, there is a good machine shop in Mountain View that will make short work of those by using their ultrasound method. I once broke one on my 914/6 engine the afternoon before I was to leave for a Porsche Parade. I pulled the entire engine, put it in the front seat of my Rabbit and took it to this shop. About a half an hour later they had it clean as a whistle, and I put it back in the Rabbit and took it back to my garage, and put it back in the car. Left that night for Oklahoma just a couple of hours late. I am so glad I did it that way. Now I use anti seize on all exhaust studs on my 911 engines.