dillon410021

Doing head gasket tomorrow(wide fire,stock studs,etc) What torque spec do u use? I tried the 15-20ft-lbs then 2 90° turns on my last motor and i really didn't like how they all feel different as far as torque. Anyone do just 3 stages up to 70ft-lbs or similar?

Thank you

87944turbo

I do up to 85 ft.lbs. in 3 stages, leaving plenty of time between each one. At least on the 951 at home. We have changed a couple on N/A motors at a race and left virtually no time between stages, but still take them up to 85 with good success. Only have ever used stock studs, but have done this with stock and MLS gaskets.

Adonay

I see your point on unequal torque.
That is the way i choose to do it with the stock studs, never had a issue with the 90°deg metode. my mechanic use a 3 step but not as much as 85ft.lbs

dillon410021

I did 3 stages. 20ft-lbs, 45 ft-lbs, 70 ft-lbs. All is well, car is back on the road. I felt must better knowing each head bolt/ stud was of equal torque

87944turbo

That's good to hear. I have seen engines that wouldn't seal completely at 65, but would seal at 85. I think in the end that had a lot to do with the head and block prep on that particular car.

I'm with you on torquing to a spec, never liked the angle method.

snb13

Check this out (it gets interesting around post #15):
https://rennlist.com/forums/924-931-...bly-wrong.html

Adonay

Very interesting thank you for that link i think i will stick to the 90deg way after reading that.

Auto_Werks 3.6

I see the most logic in the angle torque method. there are a lot of things in the factory service manual that are done the "engineering way" rather than the "mechanics way", and this is certainly one of them. I have wanted to study fasteners more, but I rarely find myself with enough free time. I know that there are many variables that can effect accuracy when using the friction torque method (click or bending torque wrench). The repeated use of the fastener (thread wear) can have an effect as well as the condition of the washer. You can actually pick up additional torque if the washer wears smoother, as the nut drag will be less and the wrench won't click until more strain has been applied. This also goes for accidentally getting silicone gasket maker on the threads... look the eff out, because you can snap a fastener before you feel any torque build up. I suspect this is why high end fasteners like ARP spec a lubricant to be applied, which is probably easier to reproduce than dry factory new condition is. ARP, and I'm sure other brands, also give the torque value in physical stretch length if you have access to both side of the bolt (connecting rod for example).

Anyway, you can always over think anything. For me, I'll go with the angle method if I have a choice.

marky522

Good luck finding a torque spec that ISNT an angle in current model Porsche's - cam cover bolts are aluminum and are torque Angle...

Mark

snb13

I used the angle method. 25,000 miles later no problems.

rlm328

I also use the angle method. A couple of rebuilds but never because of torqueing issues.

87944turbo

This is an interesting topic. And I am in now way taking sides. But keep in mind that the even with the angle method, your first reading is based on a torque value of 15 ft.lbs.

If that measurement is not evenly measured across all of your head studs, the result of the two 90s that follow will have variance between them.

Also remember that generally speaking, at the far ends of the range of any measuring device, you will have the greatest amount of innacurarcy. So depending on the range of your wrench, you could be very near the low end of the measured range at 15 ft.lbs.

Regardless of torque method, careful prep of the block, head, hardware, threads all contribute to your success.

It would be really interesting to complete a hybrid test, using the values of 15, 50, 85 and measuring the angles required for the second and third values just to see how they compare to the two 90s.

gruhsy

Very good points.

Another thing to consider is having your torque wrench calibrated.

At my work we have all torque tools calibrated on an annual basis.

There is about 30 different torque wrenches we use to cover all ranges and allow a mid-range of torque on the tool to be applied.

Probably more than most would do for their cars but, hey if you can why not???

Droops83

I believe that I have posted this here before, but I will do so again. Anybody who does any kind of work with fasteners, from DIY-er to professional mechanic should buy this book and read it from cover to cover:

https://www.amazon.com/Fasteners-Plu...ith+nuts+bolts

Some of the information is dated, but the fundamentals are still the same. You need to think about what you are doing and what you are trying to achieve when you fasten parts together.

In the case of cylinder head nuts or bolts, the goal is to achieve the amount of bolt/stud stretch necessary to provide the ideal amount of clamping force to hold the cylinder head onto the block against the forces of combustion, while also ensuring the proper amount of head gasket crush as specified by the gasket manufacturer.

There is a good reason that Porsche updated the head torque procedure. Torque-angle is always the preferred method for critical fasteners because it eliminates the possibility of friction between the male and female threads and/or the nut and washer causing a false torque force reading.

A perusal of pages 15-10 and 15-10a of the factory manual reveals exactly why the change of the head nut torque procedure occurred. On the original page, the instructions are adamant that the head nuts and washers need to be replaced every time, and the nuts and washers should NOT be lubricated (only a light coating of engine oil on the stud threads is necessary to reduce thread friction). The washers should not turn at all (use a Sharpie or paint marks to mark the starting position of each washer), and that the bosses under the washers should be roughed up if necessary to prevent them from turning.

The page with the updated torque angle procedure does note that the stud threads should get a light coating of oil, but makes no mention of the washers turning or not (though it still does say to replace the nuts and washers every time). This is because by measuring torque angle, the necessary amount of bolt/stud stretch and clamping force can be achieved without interference from friction of the threads/washers. It is likely that Porsche technicians were having difficulty in reliably achieving the original torque-force specs without spinning washers and ruining head gaskets . . . . .

The bottom line is that with the torque-force method, there are too many variables to ensure proper bolt stretch and clamping force, from thread cleanliness to thread lubricants (or the lack thereof) to the accuracy of the torque wrench and the proficiency of its user. Hence the change in the manual!

Chris

dizzyj

I twist em till their tight then givem a bit mowr. Never had a problem