tap snapped into valve cover thread

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mjo

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Jun 6, 2004
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Hi,

A while back I tried to chase a valve cover bolt thread (that enters the head) with a tap. The problem I was trying to fix was a bad thread that was snapping off valve cover bolts. I went too far with the tap and it snapped off. Now I have shards of hardened steel left over from the tap in the threaded hole and a valve cover that isn't torqued evenly. Because of the uneven torque sequence on the valve cover - it's leaking oil. Does anyone think I can rectify this and what would you use? Thanks for any help
 
second thought can you buy a aftermarket heavy cast aluminium valve cover? that and a good gasket with a silicone sealer may seal even without 1 bolt.
bruce
 
There is a pfocess called broken tap disintigrator that can be used if the hole can be reached easily. Talk to a GOOD machine shop.
 
An EDM machine could machine the tap away, but they're kind of specialized. You'd have to take the head off unless someone makes a portable one.
 
yeah call up a machine shop. they can come out to youre location and get the tap out. i had the same problem, only i broke an easy out off in a valve cover hole.

didnt take them hardly 15 mins and they had me a new slightly oversize hole. instead of using a 10mm bolt i now have a 12mm!
 
I read about this technique in a Gunsmithing tricks and tips book.

Heat the broken tap red hot with a oxy-fuel torch. Once red hot, turn off the gas, leaving the O2 on. The O2 will melt the broken piece of tap that's more easily removed.

I've never done this myself nor have I seen it done. I bet it's a pretty neat thing to witness.

You can try an industrial supply house and get a broken tap remover.
 
There are tap extractors for this. They work on straight sided taps, not spiral ones.
Also, you can try working it out with a punch and small hammer.
Possibly it can be shattered and removed, also.
A good application of quality RTV on a very clean surface will seal well, if you let it dry thoroughly, even without the bolt.
 
If it's not leaking too badly, drive it to the machine shop. A good machinist can remove the snapped tap, on the vehicle, and it should only take about 10 minutes (and a case of beer if they don't charge you). This is not something any decent shop hasn't dealt with before.
 
Broken tap removal is a simple thing with the correct equipment, so I'll echo the others that have suggested going to a good machine shop and have them remove it.

As far as a gunsmith using a torch and Oxy to cut the tap I doubt this is a viable means for firearms or your head. The extreme heat will be injurious to the parent metal and the associated gaskets near by.

I smith high grade and high accuracy firearms and I would never resort to this approach, it is far too dangerous.

The machine shop will use a bit of acid and electrical current to accelerate the etching process to free the tap remaims from the head. This will etch the currently galled/jammed surfaces between the tap and the head with minimal material removal and concentrated in the bounry line between the dissimilar metals. It will also act on the chips that are still in the flutes to reduce the force required to remove the stuck tap. Then they will neutralize the area to kill the acid.

They should then chase the tapped hole for you or if things are really bad advise you that you need to enlarge the hole and tap to the next larger size thread. If this is the result have them do this for you and pay them with a big smile on your face. You just saved the need to remove the head

Do not try to work the tap out with a punch or use a broken tap extractor that purchases on the flute relief. This will only make things worse. The cut chips that are still in there will agravate that attempt.

Yes, I've been there and done that and I've made all of the mistakes that I caution about.

Please do the right thing and get this dealt with at a shop, you'll be very pleased if you do, and probably miserable if you don't. John
 
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