Alpine951

As you can see from my recent post, my head gasket went. On clarks garage it shows three torque steps to torque the head. After the first torque step the 2nd and third don't say a certain torque but say something like 90' angle torque.

Jfrahm

90 degree turn of the bolt. I use a breaker bar so there is no confusion.
The idea is to stretch the stud a certain amount. It's better than just measuring torque, as that is affected by goop on the threads among other things.

-Joel.

OriginalSterm

superior angle method, or something to that effect. right?

Alpine951

Thats what i thought it might mean. here is what it actually said:


Step 1: 20 Nm (15 ft-lbs)
- - Step 2: 90° angle
- - Step 3: 90° angle

Do I use the old bolt or does this apply to new ones only?

Ski

It applies to the bolts. If you have a set of FS manuals, there is a max height in there to measure IIRC. hint, use a 12pt socket which makes it easier to get straight and 90° turn each time. Also, find you a predetermined way to mark each nut after torque sequence so you don't loose track.

TT

Torque angle gives a consistant crush depth of the head gasket.

90 degrees is pretty easy to measure, but you can also use a torque angle gauge, they come in 1/2" drive.

Just did this job last night.

Chris Prack

It actually applies to the head nuts. You want to use new nuts and washers and lightly oil the threads of the stud when installing the nuts.

Porsche updated the thickness of the nuts and only the new part number should be used.

Danno

You know what I've works well? I like to use a 30-60-90 lb•ft sequence on the head-studs (thanks Frank ). Porsche already updated their torque-sequence in '91 and I think it could use a little more tension.

About 1/2 of the blown headgaskets I've seen are due to lean hot combustion burning through the compression-ring, which stays perfectly round. The other 1/2 of them have non-breached compression-rings; but were ovalized out of place. This appears to indicate insufficient clamping tension from the head-studs.

This problem is similar to the ones on the '86-92 Supra Turbos. Insufficient tension on the headbolts (rather than our studs) would cause them to loosen up over time from heating, expansion & contraction. The bolts would back out and lighten up on the headgasket, which then blows out. Their remedy was to increase the final tightening torque by 15% from 70 lb•ft to 80 lb•ft; and I like a little more than that. The 944GTR that raced in the IMSA series used larger 14mm head studs and was torqued down to 150 lb•ft !!!

bigmacdave

Hello,

I have a question about this as well.

I have the 87 shop manuals and they say

Step 1 20Nm
Step 2 50Nm
Step 3 90Nm

Am i assuming correctly this is the same as the listed on Clarks?
Step 1: 20 Nm (15 ft-lbs)
- - Step 2: 90° angle
- - Step 3: 90° angle

If i set the first at 20Nm, will 90° on the next two steps get me to 50Nm and then 90Nm. I guess I'm asking if they both mean the same thing? I know about pre-loading and step up, but I'm a bit confused when i see the manual say one thing and other places say something else.

Thank you,

David

V2Rocket

No..
earlier cars came with actual torque figures like the ones you listed.
on later models they switched to the torque and then angle turn mentioned in this thread.

going by angle has potential to be more accurate than a pure torque spec due to variance in torque wrenches (but 90 degrees is 90 degrees, anywhere).

however in all the engines i've worked on i just use the actual torque figure specs and haven't had an issue.

951and944S

All of the big 3 tool companies, i.e., Snap On, Mac, Matco have digital torque wrenches with angle built in.

After the initial torque, you can set degrees to appreciate to any degrees or depreciate to -0- as you tighten.

T

Jay Wellwood

Angular Turn of the Nut Method - https://www.appliedbolting.com/turn-of-nut-dsq.php