Pulled head studs?

[Dick Shift]

I have 1999 Boxster 2.5 with pulled, yes I said PULLED head studs. Sounds like a air cooled 2.7???
Head bolt threads are in a @ 8" deep hole. Anyone herd of this one and possibly fix? Other then replacing the case.
Mahalo and Aloha, DS

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: Common Boxster Engine Problems and Failures - 986 / 987

[Wayne 962]

Hi there. I'd bet you a steak dinner it's not "pulled head studs". Studs just don't pull out of aluminum - not even on the 911 motors - they snap before that happens...

- Wayne

[BYprodriver]

Boxster engines don't have any head studs! Boxster engines do not have any studs, only bolts. I can only think of 1 nut on the IMSB flange.

[Dick Shift]

BOXSTER 2.5 motor is apart and four on one side the cylinder head bolts were not tight and came out with the threads. I suspect over torqued. Still not sure if fixable.
No worries Wayne I'm a vegetarian anyway.
At this point I will look into another case or engine.
From my experience On 911 air cooled motors; Starting with the Magnesium case 2.7 studs PULL. Like crazy!
Alum. case [3.0, 3.2, 3.6 ] engines with Dilivar studs, BRAKE.
Steel studs in Alum. case NO pulling [ if not over torqued ] or braking. EVER!

[BYprodriver]

The head bolts thread into the STEEL crankshaft housing, so you just need a good crank housing & new set of head bolts. The crank housing is removable from the case.

See the head bolt in the center of the housing:

[Dick Shift]

Thank you BYprodriver! I'm in.
I found;While the crankshaft housing or cradle uses steel to support the main bearing saddles it is all cast into an aluminum housing/cradle. VERY sturdy looking! The head bolts tread into the aluminum portion. I will simply install case savers replacing all the alum. head bolt threads.
In the future I thinking all water cooled engines should have this done when down this far.
Mahalo for all everyone's help! DS

[Dick Shift]

Warning; the engine pulled some of the head studs do to the factory head torque to much for the aluminum treads in the crankshaft bearing housing. I personally tightened the head bolts @ 8 mounts ago. To the below values.
1st step tighten to 23 ftlb
2dn step loosen all bolts
3rd step tighten to 15 ftlb
4th step add 60 degrees
5th step add 60 degrees.
lessen 5th step to 30/40 degrees? Any one with experance on this subject? Please advise.

The fix; Case savers.[M10x1.5x24mmTime-serts] same as used on the air cooled 2.7's cly.head studs.
Note pictures.

[Dick Shift]

Boxster engine advice needed.
Goal to build one good engine out of three 2.5 Boxster engines I have. Two had a cly. sleeve move down toward the crank. All IMS bearings good BTW. OK questions:
1. Prepping the one good block for new rings. Looks like air cooled Alusyls cly coating? Conventional honing? OR Use Scotch Brite pads buy hand, as we do w/Alusyls.
2. Was my pulling head studs out of bearing carrier, when torquing down heads in my first 2.5 head gasket replacement common? See above. Wondering if I need to go threw all the trouble of Time Serts? Never herd of anyone else having that happen to them. Factory head torque specks to high?? maybe? Sure seem like it to me.

[Scnell Gelb]

Yes, studs, not bolts.
Suggest you investigate using an ARP stud kit.
I used one for my M96 rebuild. Perfect.

[Dick Shift]

Your wright I meant bolts.
Didn't know they made ARP studs kits for water cooled Porsche engines. Will check it to it.
Thanks Scnell Gelb

[Dick Shift]

ARP and RACEWARE head stud sets for 986/996.997 engines very expensive.

What about the head torque sequence that seems to tight??
1st step tighten to 23 ftlb
2dn step loosen all bolts
3rd step tighten to 15 ftlb
4th step add 60 degrees
5th step add 60 degrees.= over @ 100ft./lb's torque. too much for aluminum??

lessen 5th step to 30/40 degrees? Any one with experience on this subject? Please advise.

[Scnell Gelb]

The ARP torquing procedure is much simpler than what you describe above.
More important ARP use studs not bolts.
If you compare the ARP studs+nuts to the OEM Porsche bolts you'll see the ARP parts are good value IMHO.
Check directly with ARP for the M96 studs - same as 996 engine. They will have the cross reference for the Boxster because I gave it to them. Ask for "Alex" at ARP.
To confirm ,he may ask you for the length of your bolts.
Also consider the rod bearing bolts from ARP.The Porsche ones are known to fail.
Theses are not the items to 'save' on. The incremental cost compared to OEM is very justifiable because the OEM parts are such lamentably poor quality/design.

[Dick Shift]

Re: ARP Head studs advice. Sounds good.

Re: ARP Rod bolts. With new OEM rod bolts torqued to specks. I had a rod bolt fail on a fresh 996 3.6 overhaul. So I will never use a OEM rod bolt again! Regardless of cost.

Mahalo; Scnell Gelb

Next question: How to prep [if at all] the cylinders walls on a Boxster 2.5ltr engine for new rings?

[Scnell Gelb]

Forget the bore prep until you have :
Measured for taper and ovality to determine if they are worth saving.Not an easy task.

[Dick Shift]

If it passes the taper and out of roundness checks then what?
Scot brights like on a air cooled Alusil cylinder?

[Scnell Gelb]

The only reason I cleaned the bores on my M96 was to inspect for fine cracks and to be able to accurately mark the many measuring points with a Sharpie.
I used acetone on a 'white' Scotch Brite pad for cleaning.Do not saturate the bore with acetone! You want to remove any loose carbon and 'dirt' but leave the alloy 'saturated' with oil.
I suggest you research the whole bore/taper measuring issue.
It requires special tools, pains-taking calibration of the tools,practice using them, multiple ,replicated measurements, charts of measurements. It takes hours to do correctly.
You will be measuring to +/- 1/10 of 1 thou. That is very difficult to be both accurate and consistent. It is so picky that you have to make sure you do it at a stable ambient/crankcase temperature. Even the temperature of the measuring tools is critical at that degree of accuracy. Yes, it is extremely tedious and the tools are expensive !
I doubt many diy rebuilders do this and if they do ,the results may be inaccurate. I get the impression that many diy rebuilds are just slapped together and quickly sold. I plan to keep my car so I made my measurements on multiple occasions and got very frustrated trying to replicate the previous measurements exactly.
If the subject interests you, I suggest you start a separate thread on the bore taper/ovality issue .There are no Porsche specs that I know of so I resorted to guessing based on Jaguar specs.for their Nikasil (not alusil I know)engines Who knows if that will work !
Then inspect the plating on the piston skirts for wear(wear = need new?) and measure the crankshaft journals and all the camshaft bearing areas.
I could go on but just wanted to give you a clear impression that rebuilding an M96 is correctly way,way more complex (& expensive!!) than I had anticipated. So know what you are getting into before you spend much more ?
I wish Wayne or Jared Fenton would write a book on the M96 rebuild procedures.

[BYprodriver]

Originally Posted by Dick Shift

Boxster engine advice needed.
Goal to build one good engine out of three 2.5 Boxster engines I have. Two had a cly. sleeve move down toward the crank. All IMS bearings good BTW. OK questions:
1. Prepping the one good block for new rings. Looks like air cooled Alusyls cly coating? Conventional honing? OR Use Scotch Brite pads buy hand, as we do w/Alusyls.
2. Was my pulling head studs out of bearing carrier, when torquing down heads in my first 2.5 head gasket replacement common? See above. Wondering if I need to go threw all the trouble of Time Serts? Never herd of anyone else having that happen to them. Factory head torque specks to high?? maybe? Sure seem like it to me.

I have never heard of crank carrier threads pulling out, the 1st design head bolts were 234mm long, soon updated to 230mm 10.9 grade, I wonder which you have? Be sure your head bolts have Torx55 heads. If your other crankshaft & housing assemblies are in better condition I would use it while keeping the crank assembly "married" to each other. I always clean & chase all threads before assembly. I have always used LN "Nickies" sleeves for rebuilds so all I can advise for cyl prep is don't remove any of the lockasil & use Joe Gibbs break-in oil for initial start up.

[Dick Shift]

SG & BY Thank You, Thank You, Thank You! for sharing your insight.
Re: don't remove any of the lockasil & use Joe Gibbs break-in oil for initial start up. This is the kind of advice I seek!
I am a 30yr Porsche mechanic trying to get up to speed on the water cooled engines.
Re: LN Engineering "Nickies sieves" [thow be it w/pistons & rings]at $4,600 on a $8k Boxster, or even on a $ 17k Carrera. Is not going to very marketable.
I have found lots of choices of rings for all the larger displacement water cooled engines so must be more compatible to re-ringing. Different material on cylinder walls?
I've talked with a couple of Porsche mechanics and they reuse 2.5 Boxster rings on low buget repairs if miles not to high.