IROCaholic

Well just when I think I cant do anything dumber I did it. The guy who had my motor before me cross threaded the crank bolt that holds the balancer on and when I tore it down this time the threads we just to weak to tighten the balancer back on. So I decided to drill it out and tap some new threads. Easy enough right? So everthing was going fine until I got the tap half way in and it broke. So now I need to get the broken piece out and I know its going to be a pain. Anyone has any tips or secrets to getting this thing out? I tried to use a small drill bit to back it out but the its broken at an angle that didnt work. Help me out here guys?

RBob

iTrader: (1)

I feel for ya. Last time I broke a tap (3/8 - 16 at that) this is what I did. Used a propane torch, quick-freeze, hammer and punch. Quick freeze is basically freon (r-134 today) and can be obtained at an electronics supply house. Used to cool parts for thermal testing.

Heat the tap with the torch, then hit it with the quick freeze. The sudden cooling micro-fractures the tap. Did that a couple of times, then chilled it and wacked it with the hammer and punch. Tap broke apart from the stress. Pieces then just fell out.

>NOW<

I am not sure how good of an idea this is when it is the front of the crank. Where I used this technique was a non-critical area.

You can modify this and just chill it, then wack it with the hammer and punch. Spray the quick-freeze directly on the tap, not the whole crank snout. Just remember that the rear main is absorbing the hammering. May end up having to replace the bearing at a later date. OTOH, as it is will need to pull the engine and tear it down to get the tap out.

RBob.

Sonix

iTrader: (1)

ooh, you're in a world of hurt right now

You're right, don't try to drill a tap, you'll mangle the crank beyond repair, the tap is far too hard, the drill bit will just wander.
Rbob's idea sounds pretty great. If this is a stock crank it's just cast iron, it'll be heat treated by the bearings to case harden it, but I don't think there's anything you can damage from doing this. Hopefully you can break apart the tap more with the temperature than with the hammer blows. Maybe use a small cold chisel to try to break up the tap?

Once you get it out, you're still where you started, ie no threads. Try to buy a high $$$ tap, and USE LOTS OF CUTTING/TAPPING FLUID!!!
Go slow, 1/8 turn in, then bring it out a few turns.

The balancer bolt there is mostly use to bring the balancer on. Once it's pressed onto the shaft, that bolt can be removed and the balancer isn't going anywhere. Where you thinking of using a helicoil after this?

Pat Hall

iTrader: (31)

A heli-coil repair is probably going to be your best bet once you get the broken tap out. The original threads are probably going to be pretty mangled. Once you hit the broken tap with freon, if you have an air hammer available, use that with a pointed tip punch to break up the tap. The rapid, hard taps from an air hammer should break it up a lot easier than using a hand-held hammer and punch. Pick up a small bottle of cutting/tapping fluid, and use it on the drill bit when you're driling it out for the heli-coil. Also use it on the heli-coil tap. WD-40 works ok, but cutting/tapping fluid works way better. Don't go more than half a turn at a time with the tap, then back it out some and use comressed air to blow the chips out. I'll usually back it all the way out a couple of times, blow the tap and the hole clean w/compressed air, and put more tapping fluid on it.

IROCaholic

Thanks for all the tips guys. I think I am pretty much screwed here. The engine is still in the car and messing with all of this stuff is going to be hard at the angle I am working at. It is worth a try though considering the alternative is to pull the motor out anyway. I am going to pick up the necessary equipment tomorrow and probably get started then. Thanks for the help.

Sonix

iTrader: (1)

Remove the front clip (front bumper) so you have some breathing room.