First Engine drop - nasty surprise.

[greasemonkey]

With the help of some great friends, I removed the engine ('78 SC) from my car at the weekend. (massive oil leaks and blue smoke on startup - head studs and guides?,.. we'll see)

Immediately I noticed the following. Is the consensus that this is the remains of a broken bolt just ground flush to get the 'box on. Or is it a load of weld that some one started to drill/tap and gave up?

Does this bolt-hole go all the way through? Will I be able to get to the end of the broken bolt the other side to get it out?

Should I punch the center and drill as much out as I can and then try and use a left handed stud extractor?

I look forward to the Pelican collective's response

G.

[304065]

That looks like some prior owner snapped the bolt that goes there. Studs on the lower two holes, bolts in the uppers. Probably decided to really torque down on it and then crack. Couldn't get the bolt out so just ground off the jagged stub and left it.

No, those holes don't go all the way through. They thread into bosses cast in the aluminum of the case. I would thoroughly clean everything, cover the gap between the flywheel and case with something so you don't get chips in there, use a good punch to mark the end, then carefully drill the stud, starting with a small drill and working your way up, and use your e-z out with plenty of heat from a heat gun and PB blaster to ease the stub out.

The reason for the elongation of the hole is that somebody tried this and gave up. Probably because the drill couldn't get a purchase on the end of the stud. Hence, a good punch and the graduated drill trick are key.

It doesn't sound like you plan on splitting the case but with it torn down to the crank you could probably take it to a specialist for extraction, but I would be infinitely cautious of chips falling into the open case. If you were closer I'd say "send it to Ollie's" but alas Lake Havasu, AZ is a long way from Hertfordshire!

[Flat6pac]

That is an SC and it is a broken stud. You need to try and center punch it and see if you can drill it out. The reverse drill is an excellent idea. The threads are 3/4 inch deep, just to see you can pull the one next to it and on the stud the most threads go on the nut side.
Another option is the high speed grinder, work on the center of the stud and see if you can get an ez out to firm up, little heat wont hurt either.
and a good local machinist can do it too....
Bruce

[YTNUKLR]

Sounds like a complete rebuild to me. It sounds like you need to do a full top-end on the motor, that's most of the rebuild, it's not a lot more to do the bearings and clean up the bottom end for a completely fresh motor.

In that case I would take the case to an EDM machine shop and have the stud vaporized. Then use a bolt extractor to remove the threads. Then you want to chase the threads 10x1.5 and put a new stud in with loctite threadlocker.

It is possible to just set it up on a mill if you have a machine big enough, clamp it and drill out the stud. Helpful to use a small end mill to get a flat surface where you want to drill, then use a countersink bit to get a center, then use a small drill bit to make a hole in the center of the stud. Work your way up in drill sizes until you are at about 1/4" (6.35mm) and then try the bolt extractor

[Flat6pac]

He s in the United Kingdom.

Bruce

[YTNUKLR]

Yes, I saw. What do you mean by that?

[304065]

The beer is better.

[YTNUKLR]

That's for sure true !

[greasemonkey]

Gentlemen, thank you for your responses.

I guess I should have been a little clearer - yes I'm stripping the whole engine down for a complete overhaul.

Although I'm an IT guy, I now feel comfortable doing the centre punch and staged drill process - I'll let you know how it goes.

As for the beer,...we'll that could have a whole BBS all of it's own. But yes it's totally different here to your beer. It's warm, brown and pretty much flat. And at about £3.90 a pint in the pub, it makes you equate it to porsche parts! However, as it's just below zero here at moment, it is nice to sit in an 'Olde' English pub, in front of an open fire, sipping on a pint of Winter Warmer,....

[neilca]

Geasemonkey,

I would suggest bolting the tranny back up to the engine and make a drill bushing that would insert into the tranny case to maintain your centerline. Use a cobalt drill, high speed steel will walk all around, cobalt will cut like carbide but have better flexability. I would also suggest planning on using a helicoil for this hole. That will make it good as new.

Good luck,

neilca

[Flat6pac]

Thread insert or case saver, solid unit, not the coil.
Bruce

[MBEngineering]

HI Geasemonkey
I have time-sert's if you need one fitting, or the stud/bolt removing, give me a call?

regards mike

[JJ 911SC]

Originally Posted by MBEngineering

HI Geasemonkey
I have time-sert's if you need one fitting, or the stud/bolt removing, give me a call?

regards mike

+1 on Time-Sert's

Mike

I'll be in Barrow in January, PM on your way.

Cheers

J.J.

[Walt Fricke]

Actually, none of the four holes are blind. They all are drilled through into "external" (i.e., not interior to the case where oil is) areas. At least that is what examination of a motor on my engine stand tells me.

However, only those on the left case half (right side if looking at the case from the flywheel) have backsides which are accessible or otherwise might be useful. This will be clear once you disassemble the motor.

I think these holes are also tapped through, which augers well for reverse drills and some form of e-z out or other broken bolt extractor, because it suggests that it wasn't bottoming the bolt which allowed it to be overtorqued. Assuming no one tried to use the wrong pitch fastener or otherwise buggered up the threads, once you can get something into the stub to twist it, it ought to come out rather easily.

And since you are disassembling the motor anyway, fixing this will be at most a minor irritant because you can use friend's mills and other precision tools, or take it to the EDM shop. If yours is like the one I used once, the threads will be clean when you get the piece back, as the shop will pull the stub out for you after working their magic..

If the threads are damaged, Time certs and the like may in some way be better, but several of my cases have Helicoils in this exact application. And have worked just fine over a number of years. I've also used Helicoils on the transmission mounts, and those have stood the test of time. I can get the Helicoils at my local hardware store, which is convenient. Once I have sprung for the cost of the installation tool and the right sized drill bit, using the coils makes sense.

Mind, you'd need to use one or the other of these devices only if you end up buggering the threads when removing the broken stub. If you get it out clean, I'd not worry more about it. The engine and transmission mate positively into each other, so these fasteners are mostly in tension, and if you have 1/2" of good thread in there you will have all the strength you need.

I admit I don't know the torque specified here, because I just use a long handled 17mm wrench and tug them tight. Never had one come loose. Or pull the threads.

[greasemonkey]

Originally Posted by neilca

Geasemonkey,

I would suggest bolting the tranny back up to the engine and make a drill bushing that would insert into the tranny case to maintain your centerline. Use a cobalt drill, high speed steel will walk all around, cobalt will cut like carbide but have better flexability. I would also suggest planning on using a helicoil for this hole. That will make it good as new.

Good luck,

neilca

Hi neilca,

I put your idea into practise and have had some success. I made an ally rod in the lathe and drilled a 3mm hole down the middle. This slid nicely into the gearbox. I then remounted the gearbox and drilled into the broken stud - very centrally.

However, I now need to find the previously mentioned cobalt drills. I have got some very good drill bits but the stud must be extremely hard as after an hour I'm only 4 or 5 mm in!

Then I'm going to drill it out to about 8mm, again using a cobalt drill bit.

What is the next stage after that? My guess is heat and a left handed stud extractor?

Rgds G.

[Walt Fricke]

You might consider buying a left handed cobalt bit, assuming they exist. They do for more common alloy bits. With luck, as you keep drilling the thing might back out.

Some extractors (the cheap kind I tend to buy) can have problems. If your hole is small, the extractor is small, and thus not all that strong. Breaking it off in the broken piece almost guarantees a trip to the local EDM shop. I've seen extractors which aren't a pointed spiral, but are like rods with straight flutes for sides. When pounded in, the flutes cut grooves into the ID, and thus grip it when twisted. Those look like they might take more torque before snapping, but I've not tried them.

[Walt Fricke]

Also, remember that if things aren't budging, you can keep increasing the drill size untill the remaining stud wall is very thin. And take a look at a table or chart for Helicoils or Timcerts or whatnot - they will give a tap drill size, and that is larger than 10mm, so it won't matter if you bugger the existing threads, as you will be drilling them out anyway to install the insert. And with a decent pilot hole all the way through the broken piece, you ought to be able to keep subsequent drillings pretty centered and straight without a pilot?

[spuggy]

Originally Posted by Walt Fricke

You might consider buying a left handed cobalt bit, assuming they exist.

Yeh, they do - I bought a set of left-handed ones and easy-outs recently...

No affiliation: New 10 PC Bolt Screw Extractor Left Hand Cobalt Drill Bit Set Easy Out | eBay

[911pcars]

The drill bit should be cobalt alloy, not just cobalt coated. In addition, use a cutting fluid. Kroil works fine if you have it.

Sherwood

[GH85Carrera]

It is amazing what a good cobalt bit can do. Many years ago I tried to drill out a flywheel bolt on my 914. After an hour with a normal bit I had a dent. With a cobalt bit it drilled into it like it should.