What caused my Supertec Head Stud nuts uneven torque

iamchappy · iamchappy's Garage

After 600 miles driving with cylinder to head oil leaks, i pulled the engine and checked the torque on the head stud nuts @ 30lbs. more than half of them took retorquing, most about 180º some as much as 360º or more.

Copper anti sieze was used.

afterburn 549 · 03-18-2009, 10:33 AM

Ask Henry ?

iamchappy · iamchappy's Garage

I am hoping Henry will chime in. I would like to try and fix this myself, but have promised to let Henry to fix it if i cant. With all the uneven torque it's easy to understand the oily mess.

afterburn 549 · 03-18-2009, 11:21 AM

I would make it your ownership to go to him now, rather then start a lot of worthless word chatter here.
He will chime in "if "he sees this..
truly, you need to speak directly to him . That would be the Manly (or womanly) sort of thing to do..not a bunch of gossip

iamchappy · iamchappy's Garage

I'm not throwing any fault towards the Head Studs which i am certain they are as good as they get, and certainly not Henry who i hold in the highest regard, This is more toward the shop that installed them and rebuilt my engine here in town.

Henry's a very busy guy and i hate to bother him, he will advise me at his convenience not mine.

afterburn 549 · 03-18-2009, 11:56 AM

You payed him $$ right ? ??
He and you need to have a conversation.
You both owe ea other that........
Then when that is sorted out...if someone made a mistake maybe we can all learn from it post that.
If it turns out to be M.M scenario (which i doubt) then we would need to be armed.
Remember , Anyone can make a mistake...It is how it is handled that separates the no gooders from the good guys.

iamchappy · iamchappy's Garage

The shop has taken 2 cracks at it and 3 years i am not going to waste anymore of my time with them and chance it. I have no doubt they would make another attempt at it, i just dont have the confidence or time anymore, they seem too preoccupied with the race cars they service. In all honesty i like the guys over there in the shop, they tried but couldn't sort out the leaks, the engine runs fine just leaks oil, the parts (Cylinders 91 turbo and Heads 79 Sc) may not fit well together this could be the problem. If the anti seize they used was incorrect this may attribute to the nuts not holding the torque, what i've been told these dont need retorquing after break in.

I dont plan on splitting the case the problem lies between the case and the cam towers.

Henry knows of my situation, i have talked to him many times and have purchased most everything that went into my engine from him.
I kick myself over and over for not sending it to Henry from the beginning.

Henry Schmidt · Henry Schmidt's Garage

Call Me!!!!

iamchappy · iamchappy's Garage

I just got off the phone with Henry, I think we have it all figured out.

A little machine work to the heads should do it.

afterburn 549 · 03-18-2009, 03:27 PM

GREAT, Now like I said ..if it is a mistake we all could make ,Please share !!

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by afterburn 549

GREAT, Now like I said ..if it is a mistake we all could make ,Please share !!

The engine was assembled using a set of 965 cylinders (91-92 Turbo) and 911 SC heads.
The 965 cylinders are designed to use a .50 mm (.020") steel head gasket unique to the M 30.69 engine.
If the gasket/shim was inadvertently excluded the flange on the cylinder would be in essence .020" shorter than an SC cylinder causing the head the try to seal on the area at the base of the cylinder flange instead of the sealing surface.
This would create an uneven sealing surface and make the heads very unstable.
No proper seal means the heads will move causing the head nuts to come loose and oil to leak from the heads.
This is only a guess and it will have to be disassembled to verify the theory but it sounds like a mismatch with the heads and cylinders.

afterburn 549 · 03-19-2009, 08:24 AM

Henry,
If you get the time.........................
Maybe I am in the uninformed camp (as usual)
Could you explain the benefit of using 965 cyl?
What has to be done to get there ?
Where they work and no work?
Etcetera

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by afterburn 549

Henry,
If you get the time.........................
Maybe I am in the uninformed camp (as usual)
Could you explain the benefit of using 965 cyl?
What has to be done to get there ?
Where they work and no work?
Etcetera

The 965 Turbo cylinders are full finned as opposed to the deleted fin cylinders on a standard 930. Other than the cooling fins and the use of the steel gasket the pistons and cylinders are the same.
To use them as a replacement for a stock 930 set all you need are head gaskets and SC or Carrera cooling tin.
They were used in this application because they were available at a great price.

afterburn 549 · 03-19-2009, 09:59 AM

Thanx a bunch !!

mamut · 03-19-2009, 05:44 PM

Why the 930 cylinders weren't finned?? stronger perhaps??

Henry Schmidt · Henry Schmidt's Garage

The cylinder fins were removed in an attempt to promote a more even cylinder expansion and contraction.
The lower portion of the cylinder was staying hotter than top during cool down and this caused a leak around the heads.
The thought was if the fin were removed from the top of the cylinder that the contraction would be more consistent.

lite75 · lite75's Garage

Henry,
Do you feel the half finned cylinders have any cooling issues great enough to exclude them from use on a modified turbo build?

Thanks, Dan

patkeefe · 03-21-2009, 04:54 AM

Chappy,
I am glad to see you are sending that engine to Henry; that tub of yours deserves to be done right. You need to be driving that thing! It is the nicest teener on the planet.
Pat

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally Posted by lite75

Henry,
Do you feel the half finned cylinders have any cooling issues great enough to exclude them from use on a modified turbo build?

Thanks, Dan

I believe that cylinder head temps are far more worrisome than cylinder temps.
Over the years, I have seen some very reliable, high horse power engines built with factory 97 mm 930 cylinders that performed with little or no problems in reference to cylinder issues.
One race team from the mid 90's ran 3.3 cylinder exclusively in their 600 + hp engines and if memory serves me, they ran at the front and had little or no reliability issues.
That said: you can't have too much cooling on any high performance engine. I have never seen a partial fin cylinder on a factory built race engine.

lite75 · lite75's Garage

Thanks for the reply Henry.