Broken exhaust bolts. HELP

[builtbyben]

I have a customers 996 in for valve cover gasket replacement. Even with an oxy acetalyne torch and the bolts thoroughly heated glowing cherry red hot, EVERY SINGLE EXHAUST BOLT BROKE. It wasn't even like I got them to turn they snapped almost instantaneously. Stromski racing sells an extractor kit to drill the bolts straight. Is that literally the only option? I have spent the last 2 hours try to weld on nuts but those are just breaking the stud further to flush with the head. I am praying I do not have to remove this engine over crappy exhaust hardware. Has anyone dealt with this with any success? Thanks

[JFP in PA]

Welcome to RennTech 

 

I am not aware of another or better tool for this than the Stomski unit, particularly if trying to do the repair with the engine still in the car.  It is the tool we have used when required.

 

Good luck!

[builtbyben]

I’ve managed to very carefully drill out 2 already out of the 10 but due to not having straight access to drill the holes on center I’m worried the stomski unit may not work either. Going to purchase today and see how many more I can get out without 

[builtbyben]

5 out of 10 down but I cannot drill several straight on as my drill Chuck hits the edge of the block. Had to order extra long extended drill bits. May have to remove thermostat housing and drain coolant too. This job SUCKS. Molten metal chips stuck to every part of my sweaty body lol. To anyone who ever has to do this job, I wish you luck! Cutting lube and high quality drill bits have been my best friend. And make sure you drill straight! About 20mm of bolt engagement and 23mm threaded hole depth, you can feel the drill bit enter the 3mm pocket above the bolt when you get through it. Do not keep going or you’re in the water jacket! 

[JFP in PA]

Never said it was fun.  When you are done, replace the bolts with appropriate sized stainless steel Allen head screws, use SS lock washers and brass nuts to reattach the header; the brass nuts are sacrificial and can be thrown away after use, but the SS screws will stay like new forever.😉

[builtbyben]

Managed to get all 12 (I was mistaken on the number earlier). A few important notes for anybody attempting to tackle this. 
 

1) USE REALLY HIGH QUALITY DRILL BITS! If a bit breaks in the head, you’re far f***ed

2) Use tons of cutting grease/fluid after every 10 seconds or so of drilling to keep bit tip cool and lubed. Make sure not to strain harden bolt going as fast as you can. Take your time and clear chips out of flutes often. 
3) DRILL AS PERFECTLY STRAIGHT AS HUMANLY POSSIBLE. Can’t stress this enough. If it’s not straight you will drill the bolt and the head out. When you go to tap, you may dislodge the remaining broken bolt piece. This will cause tap to seize up and hole to be ruined. Then you’ll have to go over size with helicoil

4) You will need extended (6” long) drill bits in sizes 3/16, 1/8, 1/4 and 17/64 (or letter J 7mm). Drill but  stops help too. DONT DRILL PAST THE BOLT OR YOU ARE IN THE WATER JACKET! I drilled in steps. Smallest to largest. Smallest pilot hole through center. About 20mm of thread engagement to drill through and a 3mm air gap in between end of bolt and head so when you get through you’ll feel it. Don’t keep going! 
5) You will have to remove the thermostat and drain the coolant in order to be able to drill that last one on drivers side straight on. The thermostat housing eclipses the bolt by like 1/4”. Also, undoing the mounting for the coolant tube helped make room for drill head.

6) Stainless hardware or very high grade hardware and nickel anti-seize will last forever. I also used a torch and an air hammer to heat up and remove all 6 manifold collector studs and replaced with grade 10.9 bolts and nuts.

7) Have a face shield and long sleeves because it will be raining hot molten metal chips down in your face for 3 days straight 

8 If you have the funds I highly suggest stromski racings drill guide kit but it is pricey for a one time use item 

9) when tapping use grease, check x and y to make sure you’re staying straight, remove and clear chips out of flutes often and use the 3 turns forward 1/2 turn back method

10) vacuum fill the cooling system or fight bleeding