$#!!!T% I overtightened a coil pack bolt

drill and easy out? or is there enough to grab with vice grip?

 

If there's enough of the bottom part sticking up to grab with Vise Grips and twist out, you're having a good day.

If not, but there's enough sticking up you could slot it with a Dremel cutoff wheel and screw it out with a screwdriver, you're still having a decent day.

If not, but there's a place nearby where you can pick up a left-hand cut drill bit of size no larger than the thread minor diameter (check by holding it up to the part of the bolt you snapped off, the solid center portion should be able to block you from seeing any of the drill bit), and you have a reversing electric drill to use it with, you're probably not having such a bad day. Be sure to center-punch carefully before beginning to drill so the bit doesn't walk around. The stub might just come out from the action of the left-hand drill bit spinning in it. If not, you can hammer an EZ-out into the drilled hole and turn that to the left.

Show mercy and finesse with the hammer, as the valve cover is aluminum. Also avoid twisting an EZ-out so hard that it breaks (they're brittle), because if you end up with a bolt stub that has a broken EZ-out in it, your day is starting to get bad.

If you get frustrated, there's always the option of removing the valve cover, taking it to your favorite local machine shop, and saying "please make my day better."

After a while you get a sense for the diameter of a screw or bolt and say things to yourself like "no way can 82 ft-lb be right for a bolt that size." But it's a sense that comes with experience....

-Chap

 

You might want to stuff a rag down the spark plug hole, so you don't get anything in there and making your day even worse

 

Ahh, now you will be double reading the number and ft-lb vs in-lb carefully. You learn best from mistakes; been there.
The bigger the bolt/nut, the larger the torque. You lost your perspective. Lug nuts are 76ft-lb. 82in-lb/(1ft/12in) = 6.8ft-lb

1) Cut your losses and take a good picture of the broken bolt w/ your smart phone/table, and drive this picture to reputable shops to see if this is something they could do. Depending on where in CA you live, go to Luscious Garage (San Fran), Art's Automotive (Berkeley), Avi's Advance Automotive (Inglewood).

Really go see a mechanic.

2) Take a hack saw blade, or a Dremel type tool, and manually try to cut a slot into the broken bolt, to fit a flat blade screwdriver to unscrew. Cover the spark plug hole with tape/rag/etc, so metal pieces don't fall inside.
3) Clamp on a vise grip to try and muscle the broke bolt off, but it looks like there is not enough of the bolt sticking out to grab onto.​

 

That should come out pretty easy with a bolt extractor kit. You drill a pilot hole into it, then drill into it with the extractor bit. It's got reversed thread direction: so simultaneously drilling into the pilot hole, grabbing and unscrewing the bolt remnant.

I'll keep mum about subjecting a small bolt to 82 lb/ft torque.

 

Yup. The torque for the wheel lug nuts is 76 lb/ft, by comparison.

With a little locator bolt like that, I wouldn't even enlist a torque wrench. Just tighten it down with a 3/8" drive ratchet, one-handed. With your hand covering the ratchet and fingers extending out a few inches on the bar, you'll get about the right torque.

 

If the bolt bottomed in the hole and then got cranked to mumble foot-pounds, it's probably in there pretty well and will put up a fight to get out.

But if the igniter flange was thick enough that the bolt never bottomed before it broke, it might be invited back out without a whole lot of drama.

-Chap

 

Buy a replacement valve cover on eBay for approx $50.

 

what if you just left it.

 

Congrats!

 

The good news: OP knows how much torque to apply to get the thing out.

 

i thought he got it out?

 

HDuncan was so fast, he had time to remove the bolt, run down to the shop for another, and beat me to the post.

 

Joking aside,
if that bolt came out with a naked hand, it suggests that the bolt was broken by side force way before the set torque was reached. Amazing to me that the well threads are not damaged.

 

I'm not sure. When you torque the bolt, tension builds between the head and threaded portion. Once the head breaks off the threaded portion is loose again.

 

maybe it bottomed out.

 

I think so.
It also seems that the machining of the bolt and well were to a fine tolerance and HDuncan applied a very perpendicular force all the way.

So why did the bolt not reach the well surface before it snapped ?

 

The bolt's an M6 by 30mm. It goes through an igniter flange that looks, oh, 10mm deep or so, and then into a threaded boss in the valve cover that is threaded more than 20mm deep, right? They don't want the bolt to bottom in the hole, because the whole purpose of the bolt is to tighten down on the igniter flange. Bottoming would stop it early and leave the igniter loose.

So when you try to crank the bolt to mumble foot-pounds, all you're doing is stretching the bolt in the space between the top of the flange and the threads that are engaged in the valve cover. The force against the threads comes from the tension in the bolt. Once you have stretched the bolt past the breaking point, and it breaks, there is no tension left on the part still in the threaded hole. It's just sitting there. As the OP found out.

Now if you had a bolt long enough to bottom in the hole, and you cranked that to mumble foot-pounds before it broke off, you would have a very different experience getting it back out.

-Chap