First Engine drop - nasty surprise.
 

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.
http://forums.pelicanparts.com/uploa...1352482875.jpg
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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!

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

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

He s in the United Kingdom.

Bruce

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

The beer is better.

That's for sure true ! :)

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,....

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

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

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.

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.

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.

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.

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?

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

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

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.

Walt has already stated what I would do next. If it is stuck try heating the area with a propane torch. The magnesium expands more that the steel bolt and a little movement could help break it free. Easy does it.

Hmm, looks as though I've got more to think about than the stud in the first picture,..

http://forums.pelicanparts.com/uploa...1362915544.jpg


In total there are 5 broken head studs - all lower. I'm not sure of the material yet but all the lower studs have a very feint golden colour (color ?) to them. All of the top row studs look like standard steel. Both types have very - mild surface corrosion.

Fortunately, they all seem to have broken off with 10mm or more stud poking out of the block. I intend to mig weld a nut onto the remaining piece, wait 10 seconds, then undo them with a spanner,....

I'll report on the success (or not!).

This being my first engine rebuild, I have not found it that hard and certainly not too daunting so far. The possible exception being the 46mm can nut - needed a friends help with this due to 4 hands being needed and the 46mm tool.

Yesterday saw me using a standard valve spring compressor to remove all the valves and springs (all bagged up individually). Fortunately no nasty surprises there. with 122K miles all the seats looked fine. Naturally the guides were a little floppy - about 0.5mm wobble. These will be replaced anyway.

I intend to drill the guides out to within about 1mm of the guide edge and 80% of the length. I then intend to bang them out with a drift as they will be weak by then.

I have read that putting the guides in can be a DIY job;
1, remove old guides
2, clean heads thoroughly
3, freeze guides in domestic freezer - heat heads to 200 dec C in oven.
4, make brass drift to bang the hot guides in.

Your thoughts please,...

Greasemonkey.

Greasemonkey,
even if You pull the guides yourself You'll need to properly machine the ID of the new ones afterwards and do the seats. Why not taking them to a machine shop and have all done by them?
luca

OH Dear - this is my SC 3 Ltr nightmare! TWO studs broken on that middle jug. :eek:

Please keep posting your progress - as I may have to go through that myself in the near future.

With your heads I would think again about getting a pro &/or shop to do it. If its easy for you it would be very easy for them and if there is a problem they can deal with it.

For example, during the job a valve seat may loosen up or some valve springs may be soft & its second nature for a shop to remedy.
Anyway good luck & hope there are no more hidden surprises.
Peter in Melbourne Australia
( Sweltering in 100+ degree heat!)

I'd consider pulling worn guides myself. There is also a technique which calls for drilling, but I think maybe not the full 11mm, and tapping and screwing in a bolt, whose head is used for pressing the old guide out.

But not installing new ones, as making sure the new ones are just the right interference fit OD for the holes (which probably are a bit larger due to pulling the old guides) calls for careful measurement, and having a lathe to turn new guides to just the right size, hole by hole, is what you need. New guides typically come oversize, as they are intended to be turned down as needed. Not like over/under sized bearings which come at the needed size already.

My understanding is that you want to hone the installed guides to just the right ID. The reamers I purchased, with stuff like this in mind - and because they weren't expensive - are not the right tool. And the guide ID needs attention, as again it isn't necessarily the right size, and is going to be smaller after the guide is pressed into place.

A lot of shops, even those with the tools and mechanics with general machining skills, tend to farm out this kind of head work.

Peter - I've never heard of a 911 valve seat coming loose as a result of a valve job. Even in swealtering heat. Plenty else which may be tough to deal with on a one time basis, though.

Having a valve spring checker is quite an expense for a guy just doing work on his own engine, I'll grant you. Though I wonder how often one finds a soft spring in a stock 911 which wasn't raced or overheated? The stock springs are pretty stout.

If you have the specialized tools, refacing valves and seats isn't out of home reach. Setting installed height not that tricky, though it is good to have some extra shims on hand.

But here also I know a number of shops with competent guys who find it cost effective to send heads out for at least the valve/seat facing part. Or the whole shebang - my spring compressor is marginal, so it is often a bit of a rodeo, and in my wildest dreams I see a hydraulic one dancing around.

Yikes and wow.

A friend of mine who runs a machine shop will take out a busted stud for $50.
Or $100 if you have tried to do it yourself first.
At some point you are probably going to get your case halves either cleaned or looked at by a professional.
Why not let them dig the broken bolt out for you?
If it needs to be opened up and rethreaded for a time-sert, it's best to do it on a mill and NOT by hand.

OK, a quick update.

Taking the guides out is easy. drill them out for about 90% of the length. use two drills of increasing size to get to within 1mm of the outside diameter. I used some tape on the drill bits as a marker for the depth. Then tap them out, using the ledge you have created, with a drift. Takes about 1hr to do the 12 holes and whack them out. I used a pillar drill with an adjustable bed.

I've taken all the cylinders off of the pistons and disconnected the pistons from the rods. A very easy job, but needs two people, as you need to support the piston while you tap the gudgeon pin out. Thx Cheryl! With the exception of a score mark along the length of the bore of No 1, all the pistons, rings and cylinders seem fine so far (pre-measurement).

I'm now trying to remove the head studs. Even the whole ones that you can get tools on are VERY tight. So I'm going to have to get a machine shop with oxy to heat them up a little. I'm a fairly stong guy but JEEEZ they are tight. Whilst they have the block, I'll get them to do the broken stud too.

Interestingly, I've had a number of people try to drill out or weld to the flippin' stud to try and get it out - nothing so far,.... All their cobalt drills do nothing and MIG weld doesnt seem to 'stick' to the stud.

Onwards.

If the broken studs stick out. Drill the threads out of a nut so that it will fit over the broken stud. Then TIG weld the nut to the stud. Heat the case up to release the Locktite, The stud will normally come out. If it broke of flush sharpen a bolt to a blunt point and TIG weld that to the end of the stud heat the case and remove.

you can not weld dilvar studs. I think. It is not steel

You need a map gas torch to warm up the locktite. keep warming until there it releases a tiny puff of smoke. Get the best and most expensive stud puller you can get.

Removing head studs......
 

Get a propane or mapp gas torch. Use it to heat the block inside the hole for the cylinder and next to the stud. When you can feel the warmth on the opposite side of the stud, try turning with a collet stud remover or an adjustable pipe wrench. It may take more than one application of heat. Once the block is properly heated, the studs will be fairly easy to remove. It only took me a few minutes to remove the 12 dilivar studs from my SC block once I learned the technique. By the way, my engine had 3 broken studs and one that had been replaced some years ago! Good luck!

http://forums.pelicanparts.com/uploa...1371463840.jpg

Do not stress. This is a classic on these engines. Mine had 4 studs broke. The first valve adjustment has been very hard on morale. € 2,000 pieces (ARP studs, etc.) and € 2,000 for labor.
Good luck!

Not sure about the "dilvar" base material, but real Porsche Dilavar studs are steel and thus should be weldable.

Let me know if anyone wants to buy the most expensive stud puller you can get. :)

Sherwood

They weld just use alittle stainless filler rod.

Thanks for all the replies.

I took it to a motor engineering company this morning. I asked them to do all the head studs, the one on the first thread and remove the flywheel (lazy I know,..).

These guys have been going for 40+ years and have an average age of 60 years! They are used by all the local mechanics when the going gets tough,...

I got a call mid morning to say 21 out of 24 head studs are removed, the flywheel is off and the one in the first picture of this thread is out! They used an air impact drill to get the original stud out. Never heard of one of those,... (bull$,..?)

I asked about the 3 remaining head studs to see if they had tried welding a nut to the remaining bit (at least an inch showing for all 3), and was told I need to find somewhere that does Spark Erosion. Trying my nut/welding technique "would make it worse". Thanks.

So that's £140 +VAT and the saga continues,...

Spark Erosion must be what those of you in Blighty call electron discharge machining or EDM. It is really magic, as the arc burns its way down the stubborn stud. By the time it gets out to the threads, so little is left that, if they won't just screw out, you can pick them out with a bent scribe tool.

I think of it as being used on a stud broken off flush.


With all due respect for the years of experience these guys have, welding on a nut isn't going to make things worse. The most it might do is to break off the rest of the protruding stud. Which I think is what the EDM shop would do anyway to get started. No need to burn off anything sticking out. With the heat applied in welding, the corrosion or adhesive which is making the stud not want to turn is likely going to be reduced in strength so the stud can be screwed out.

And if, by chance, using an impact gun on a welded nut damages the case threads, they are pretty easy to repair with TimeCerts or other case savers.

I'd find an EDM or whatnot shop, and then ask this shop to humor you and do the weld nut thing. And that you won't hold them accountable if somehow the results involve even more expense.

Why not thread inserts? They are used as standard on aircraft engines after all as opposed to other types of insert. Solid inserts require a larger oversized hole which removes future reparability. Just a thought!

Numerous rebuilds confirm what currently works and what didn't work as well (Heli-coil and equiv.). History doesn't have to repeat itself unless there's new technology to learn about.

Sherwood

Maybe heli-coils are more difficult to install correctly. I have used them in many applications in the past with no problems.