80SC RoW rebuild: 8 broken lower head studs! 200K KM
 

Hi all,

As posted in the main forum over the years, I acquired my 1980 911SC Targa RoW 8 years ago (180K Kilometers at that time), and soon discovered 1 broken lower head stud. Despite opinions to the contrary, I decided to keeping driving it, paying attention to changes in engine noise.

I have driven and loved this car ever since, but last summer the tell-tale sound appeared and decided to stop driving it. Had hoped to rebuild the engine over the winter, but a broken ankle modified that plan!

Total mileage now = 200K Kilometers, engine never opened up before.

Thought I would post some images here because I'm sure I will be looking for advice, and some might be interested to see what damage can be caused by driving with broken studs :eek:

http://forums.pelicanparts.com/uploa...1469633803.jpg

Solo Extraction using motorcycle lift

http://forums.pelicanparts.com/uploa...1469633860.jpg

http://forums.pelicanparts.com/uploa...1469633958.jpg

Busy stable - one has to go!

http://forums.pelicanparts.com/uploa...1469634050.jpg

http://forums.pelicanparts.com/uploa...1469634114.jpg

Deep Creep is amazing - ZERO broken exhaust studs!http://forums.pelicanparts.com/uploa...1469634181.jpg

http://forums.pelicanparts.com/uploa...1469634224.jpg

Note number of broken lower studs!

http://forums.pelicanparts.com/uploa...1469634303.jpg

Heads from cylinders 1 to 3, after some gentle cleaning:
http://forums.pelicanparts.com/uploa...1469634329.jpg

Heads, so far, don't look too bad, one small nick where one of the head gaskets is broken. Will probably need fly-cutting of all heads on that side.

Presently on vacation - will be removing the other bank when I return.

Only 200K Kilometers on this car - engine never opened before - my plan is to not split the crankcase...

For those interested, OLD thread can be found here:

http://forums.pelicanparts.com/porsche-911-technical-forum/406265-one-broken-head-stud-2-drive-3.html

Sub'ed !

Thx for the tips.

Also,

Have Wayne's excellent book as reference :)

Since relatively low mileage, plan is to remove P&Cs together; hopefully can find a thread that outlines the best sequence.

Hi all.

Back from vacation and last night I removed the right bank of heads, the side with only 3 broken lower studs!

All went smoothly, and here is the outcome:http://forums.pelicanparts.com/uploa...1470444451.jpg
http://forums.pelicanparts.com/uploa...1470444498.jpg

The heads on this side seemed to have more or less the same amount of very slight erosion as the left bank. Most of the slight damage appears to be outside of where the head gasket sits. Is this normal?

In any event, I do plan to get the heads surfaces flycut, even if the damage is very minor.

All cylinders look good, with no scoring, except #5, which has one shallow score:

http://forums.pelicanparts.com/uploa...1470444740.jpg

http://forums.pelicanparts.com/uploa...1470444788.jpg

Should I be concerned about this? I was planning to leave the pistons in the cylinders as the engine has only 200K km. I drive this car less than 3,000 KM per year :)

Cylinder condition?
 

SmileWavy

Hi all,

Asking for some advice from the experts here please re condition of cylinder (above). Thanks!

If it was mine I'd re-ring it. See what caused that score, may be a broken ring. Why go thru all that work and not do it right?

Thanks! My only concern is re-ringing it as the cylinder is Alusil... ?:confused:

Oh, I missed that! At the minimum I would take the piston out on the scored one to see what is going on. Did it burn any oil?

Yes, thanks, I will attempt that!

No, it did not burn an excessive amount of oil. Only 124K miles... (~200K KM)
Best,
Tom

Latest status:

Heads removed from left tower in prep for shipping to machanist :)

http://forums.pelicanparts.com/uploa...1470795064.jpg

Then I would most likely do the same, keep the p and c's together except for that #5. Is the score deep enough to catch a finger nail? Off thread, I see you are on "the rock", neat place, I was there on my Harley a few years ago, was heading to St John's but decided to cut the trip short due to a hurricane coming up the coast. I'll be there again in Sept, coming across Quebec and Labrador then taking the ferry from Blanc Sablon to St Barbe then down to the ferry at Port aux Basques and work my way back home. Not on a Harley this time though, it wouldn't do well on the Lab 500 gravel, LOL.

Hi Boosted. Thanks, yes, the score can (just barely) catch a fingernail.

Your Road Trip sounds great! You should visit St. John's, and see my collection ;)

Best,
Tom

See what the rings look like on that #5, if not broken then I'd probably put them back in and run it. I might visit St John's, time permitting.

Update: 6 heads cleaned, packed and shipped to machinist in eastern Canada experienced with 911 aircooled engines :)

Next task: Remove P&Cs together and the n tackle removal of broken head studs!http://forums.pelicanparts.com/uploa...1471041227.jpg

Extraction of this broken head stud is going to be a challenge!!:eek::eek:

http://forums.pelicanparts.com/uploa...1471224781.jpg

SmileWavy

That is going to be a tough one. Can you get any bite at all with a pipe wrench?

I cleaned the stud with a dremel to bare clean metal. Then I put a big washer over it ,with the perfect size hole and then I did put a big nut M12 over it. Protect your case with fire resistant cloth and mig weld the nut on. Because of the gap between the stud and the nut you get a good and deep weld. The heat will help loosen the stud. This is how I did several of mine.

Thanks, I will try welding a nut on, or use a dremel to cut a slot for a screwdriver.

Did you have any issues welding a nut onto the stud?

Tom

Hi Tom,

I didn't have any problems but make sure you clean the sides and the top to bare metal ,so the weld will be penetrating the stud and the nut. Using a non galvinised nut is best(gives less splatter and toxic smoke). The washer is for protecting the spigot. The biggest trick was to get the washer and the nut level. I did hold the washer straight with pliers and made a small spot weld onto the stud and then placed the nut over the stud. I started filling up the gap around the stud and the oversized nut and then filled the nut till the top. By the time the socket fits over the nut, expansion from heat gone enough, I backed the nut with the stud out of the case. It worked well for me on my 8 broken studs so I did also all the other ones this way but higher up the stud. I also heated the spigot up with a torch for 15 min before starting this. You mean concern is to protect the cylinder base.

When heating the case for stud removal does the heat damage the thru bolt o-rings near the heat? Necessary to replace them individually after doing the studs? Maybe a wet rag around the nut or bolt head to prevent damage to the o-ring?

Good point, in my case it was a full tear down.

I did one headstud like that, welding a nut on. Actually I have done several stud removals like that, but only one headstud.

The biggest problem is getting the weld to bite on the stud. It helps to make a spot weld on the stud first so there is a good base to weld on to. Othervice the puddle likes to just attach to the nut. Drilling out half the nut with a large drill bit to get a big v-shape groove around the stud is another tip.

You may have to repeat this procedure before having success.

Hi. Update via pictures below: Made a wrist-pin puller, removed all cylinders, and pulled piston from the scored cylinder (#5, as per above) with no broken rings :)


http://forums.pelicanparts.com/uploa...1471617051.jpg

http://forums.pelicanparts.com/uploa...1471617099.jpg

Also able to extract some broken lower studs with my Titan stud extractor with no heat :)

http://forums.pelicanparts.com/uploa...1471617141.jpg

Next: welding of nuts to studs broken close to case, in order to attempt removal.

Good news, put the piston back in and run it.

Success! Milestone achieved! All remaining broken head studs removed by MIG welding a nut on.

First we cleaned each broken stud to bare metal, then placed a cylinder base gasket to protect the surface, then a washer, then a nut with washers positioned to level the nut.

Note my favorite blue dress shirt positioned to protect the case etc :)

Welding generated enough heat to help break the bond and success; all studs backed out easily with little effort and threads intact :)

I big thanks to mhicks for expert welding skill!!

http://forums.pelicanparts.com/uploa...1472327319.jpg
http://forums.pelicanparts.com/uploa...1472327346.jpg
http://forums.pelicanparts.com/uploa...1472327372.jpg

Great, hopefully that shirt isn't the one your wife or GF gave you for Christmas:)

Back at it - timing chain question
 

Hi all,

Been a while since I posted! In August/September I shipped all 6 cylinder heads to Ontario for inspection and machining. Inspection revealed that head surfaces required only a minor (less than 6 thou) resurfacing, but valves needed replacement. So, heads were completely rebuilt, resurfaced and returned home to the stable in late September. Then I started a long business trip, then various other life items consumed my time but now I'm back at it!

I'm about to order the parts required for rebuild; studs, gaskets, chain ramps, etc.

Question: I was planning to replace the timing chains, but can I do so without replacing the chain sprockets?? Please note: I did not split the case SmileWavy

Thanks!

I d leave the chains alone if you're not willing to split the case. Snap ring on the chain will make you worry.
I was always told, if the chains are worn out so is the rest of the bottom.
Install new plastic guides as the old are brittle.
Bruce

Damage to Cylinder sealing surfaces?
 

Hi again all,

As mentioned, the sealing surfaces of all 6 heads were in decent shape; only needed to remove 0.006" to clean them up. This said, should I be concerned about the sealing surfaces of the top of the cylinders? They look fine to the naked eye...SmileWavy

Thanks,

Tom

Thread chaser?
 

Hello,

Well, after a winter of clearing snow, and acquiring parts, I'm ready to tackle the rebuild! First step is to install new studs, but should clean the threads in the case first - I know I should not use a tap - any good posts on how to make a thread chaser from out studs? A search did not provide instructions; just pictures of finished product (stud cut with dremel). Thanks!

Use one of the whole dilivars and cut across the threads to have a place for the junk to go to when you run the stud in. Blow the holes out, spray carb cleaner, blow dry. Use thread lock.
I install the piston units first then install the studs. It gives you more room to get in the snap rings.
Measure depth of the stud from top of the piston.
Bruce

Thanks Bruce, all is nice and clean now!

When installing the new (steel) head studs, is there a torque specified? Cannot seem to find a good thread about that, although I do see lots of info re deck height...

Tom

New head studs
 

Hi all.

As per above, I have cleaned the bores and am now ready to install the new steel head studs. Most of new studs can be installed all the way (until bottomed) easily by hand; no tools required. Is this normal? Considering this, I am thinking to use red thread-locker instead of blue. Thoughts? Thanks and happy motoring!SmileWavy

Progress

http://forums.pelicanparts.com/uploa...1494528136.jpg
http://forums.pelicanparts.com/uploa...1494528136.jpg