Linus

Hi, just completed rebuild of my GT engine but now discover when it's running a bad oil leak from the main oil passage that runs up through the head gasket - there's a 1/2" hole in the head gasket where the oil goes up to feed the head.
When I was tightening the head bolts (15ftlb +90 +90) I found this to be really tight even with a 24" long 3/4" drive bar. I was doubtful they should be that tight and sure enough I got the distinct impression some of the bolts started to get looser (easier to turn) during the final 90 degrees. Now I know I was not imagining it and I've partly stripped some of the damn head bolt threads in the block. Have to strip the whole thing down again totally and get them helicoiled I guess but it's particularly annoying as the engine runs perfectly !!! I sure hope they can be helicoiled !
There's my question - has anyone had this happen and sucessfully had the threads helicoiled ?
Anyone replacing heads on a 32v be damn careful when you do those head bolts !!! I know for sure I did nothing wrong and my head bolts were all in perfect condition - they looked like new when I took them out. I would wish someone had an actual torque setting rather than this +90 +90 business !

Yours sadly,
Paul

zmandan

what do you mean +90 +90 ? i heard recently that stripped threads on an alum. engine are Not that uncommon. .....and it runs perfectly.. what a shame.

dan z

Old & New

Linus,

I don't think I would do the prescribed method without a torque wrench... If the torque value reached the ultimate recommended specification for that fastener, I would stop.

There are a lot of variables; even the gaskets you used may be significantly different from those used when developing the assembly procedure, etc.

Linus

Hi again, Zmandan the +90 +90 I refer to is the way the workshop manual says the head bolts should be done up. First torque to 15ftlb then 90 degrees of turn followed by another 90 degrees.

Paul

Lagavulin

Don't tear the engine down yet!

A couple of guys have recently gone through the same exact thing as you, but the bolts were not stripped. According to Blown Beast's mechanic, the reason for the loosening/stripping feel is because of the head-bolt-washer spins underneath the head of the bolt, giving the impression of the threads letting go.

Actually, it's a very exacting and consistent way to torque something down.

Garth S

Absolutely! In the nuclear/process industries, ''torque" was best set by, in order of effectiveness,
- micrometer measure of stud/bolt elastic elongation
- a predetermined elongation based upon thread pitch and preset turms after initial gasket crush: eg, 15 ft/lbs -90-90 deg rotation.
- torque wrench
A torque wrench is a convenient way to measure tension that results from elastic elongation to give a desired compression.

Paul, Surely seems as though everything was done perfectly - except for the resulting oil leak. Regardless, it seems as if some dissasembly is ahead to cure that: by some fortunate chance, is the oil weeping fron a valve cover or cam seal?

fst951

Hi,

Did you add a little bit of oil to the treads? Did you use new or measured head bolts? I hope they didn't strip as it takes quite a bit of machine work to redo the theads. I recommend timeserts if you have to do it. You may want to consider head studds next time.

Good luck.

Blown Beast

If you followed the manuel the horrible feeling you felt was the washer spinning......I know, cause it happend to me and I too thought I had done the deed, But Greg Brown told me what happend.
Pull the bolts out and check the threads for metal....then clean the threads with a die, lube with oil, and place thin layer of grease between the top of the washer and the bottom of the bolt head.
Make sure that the seat that the washer sits in the head is clean and dry.

Your leak is probably some were else.

Kevin in Atlanta

It is my understanding that with the 2 90 turns we are stretching the head bolts. It does feel weird, though. I felt the same thing when replaced the head on my Mercedes 300E.

Linus

Hi, thanks a lot to all you guys for replies which have cheered me up a lot !! The strange feeling when doing up those bolts has to be felt to understand it but it's really like they are stripping.
I am now very hopeful that I've just got an oil leak from the head gasket - still a bummer but I will now proceed to remove that head now and check it out rather than ripping the whole engine out again.
I was so not looking forward to stripping the whole engine I was seriously considering selling the car and cutting my losses. You guys have made the decision for me. Thanks again !

drnick

damn! there goes another autotrader bargain...

zmandan

I'am still trying to understand why +90 +90 is used instead of a simple
tourq reading. the +90+90 business sounds like something you would use on a lawnmower engine not an alum porsche engine. IMHO

good luck I hope you have a no strip situation going for you.

dan z