3.2SS top end rebuild - compulsory newbie questions

[Alan L]

Exactly. You can't torque another 90 deg, nor check. It is normally used for 'set and forget' bolts.
You basically would have to do ft/lb recheck - but you have no value to work with because you don't know the original value. So all you can do is make them even - 23 ft/lb? So why not in first case.
Alan

[Alan L]

FWIW I have done engines/rebuilds and not re torqued them (my own engines/rebuilds). And had no issues. But ideally, it is advisable.
making me feel like I should go and re torque the latest rebuild.
Alan

[Nux]

Well FWIW, I'm an ENT surgeon. I have done many ears - but this is my first Porsche engine. I'm fascinated by the similarity between ear surgery and re-building these magnificent engines. There's plenty of literature, but it is also very much a apprenticeship - learning from those who have experience. What works, and what does not.

So when we find different solutions to the same basic problem, it must mean that we are operating within a significant safety margin. Which is why Bruce's method works and why Alan doesn't need to re-torque. The stuff you don't read, but learn from experience.

I really love this forum - thank you for your help guys!

ps: John Dougherty sorted my cam issue for me: 1.8-2.0 is the setting for low CR and 2.2-2.4 for higher, which is the advanced setting.

[Alan L]

I don't mind tackling a 911 engine. But I would not do ENT - even with a manual.
Stick with this forum and you won't go wrong. Yes, more than one way to skin a cat. But these are great engines. just complex and time consuming. Take your time, get it right and you will be rewarded.
regards
Alan

[Flat6pac]

Just because of age, I doubt myself at times. I ve built for a long time so the specs change with different motors, but they’re all 911.
Two things to discuss
I was correct on the head bolt torque angle for Carrera cylinders
When I first looked at the book there was torque angle on the rod bolts. I thought maybe i was wrong about the head nuts. I wasn’t.
New info on the rod bolts.
There is a new edition of factory bolts with 12.9 on the rod bolt head. This edition requires a second 90 degree torque angle.
Finally, you need to have a machinist that knows the work on the heads. I ve had the same man doing heads for the 17 years I’ve been in NC. Depend on their expertise as you have the motor apart and guides are no place to cut corners on reassembly.

Bruce
Photos taken from Carrera spec book.

[Alan L]

Wow - thanks Bruce. Waynes book doesn't mention that.
So how do you get on for re torque after 1000 miles - or do you not bother?
Regards
Alan

[Trackrash]

It is interesting that Porsche snuck in the 15# + 90 on the Carreras and Wayne does not mention it.

The question I have is about re-torquing. Or as Wayne says in his book re-tighten at 500 miles.

So the real question is, do you back each nut off 1/4 turn and re-torque?

Or do you just put a torque wrench on each nut and if it doesn't move at 24 ft lbs, call it good?

Same with a Carrera?

[Flat6pac]

If it a concern, I would go with the turbo spec @32#. Turbo spec may be less because the factory builds with 24 dilivars..but then Carrera builds with 12.
The last turbo, I used Supertec and followed Henry’s spec.
I wouldn’t back the nuts off because you’d be starting over again as build day
Bruce

[Trackrash]

Originally Posted by Flat6pac

If it a concern, I would go with the turbo spec @32#. Turbo spec may be less because the factory builds with 24 dilivars..but then Carrera builds with 12.
The last turbo, I used Supertec and followed Henry’s spec.
I wouldn’t back the nuts off because you’d be starting over again as build day
Bruce

Are you saying that for all steel studs 32 ft lbs is appropriate? Or is that just for the newer divilars?

[Flat6pac]

No, I’m saying that the numbers are for factory new build specs. Dilivars on the turbo don’t expand further than the cylinders as the steel would.
We’re just swapping ideas, I only have my experiences and thoughts.
Bruce

[safe]

I guess that the 90 degrees is more precis than x-amount of Nm.
You get the bolts snugged up with 20 Nm, then you add the desired amount of stretch with 1/4 of the thread pitch.

If I'm not mistaken the Carrera spec supersedes the older torque value for the earlier engines to?

[Alan L]

I have another w/shop manual, - which also covers carrera - which I think also doesn't mention the 90 deg torque. I can't get to it for 2-3 days but will check.
Curious. I'm guessing there are an awful lot of Carreras torqued to 23 ft/lb. But it also suggests you can dispense with the re torque proceedure.
Makes you wonder why earlier 911s can be done to ft/lb and my 930 is ft/lb, but Carreras are different. Same studs I think?
Regards
Alan

[Nux]

it would be interesting to see what a 90 degree swing corresponds to in torque? Could it be that it is even more than 32ft?

It's quite typical for engineers to include a significant safety margin, which may be reason why you dont really need to re-torque?

[Flat6pac]

Seems to me that Supertec paper work gave me 36 or 38 ft# for the turbo I’m doing.
Realize the 84 and later turbo used the same head seal as Carrera but used 24 dilivars studs so you don’t have the potential expansion as with steel.
Bruce

[KTL]

The Carrera head stud spec appears to apply only to the Carrera if you look at one tech bulletin in 1987 and does not apply the previous engines. But the 1986 bulletin says it does apply to the engines from 1978, due to an updated head nut. In other words, two separate reportings that conflict?




Note that Optimoly HT is basically antiseize paste for those who don't know this. It's nothing super high tech secret sauce.

Not sure why they would say the 90 degree application doesn't apply to the earlier engines like the SC 3.0L since the head studs and cylinders are basically the same. They also make a point of saying not to reuse the cylinder head nuts. I don't know if they state that because of the nut material or the potential that the nut's tooling hex can get damaged upon removal? But i've seen the head nuts reused on a number of occasions with no ill effects.

Since we covered rod bolts here too, here's the bulletin information on the change in the M9 rod bolts and how to torque them.

[brighton911]

Well this discussion is rather timely as I was at the head torque stage in my assembly this week. Mine is an 86 and I previously used 24 ft lb (as per Wayne's book) with no issue.
So this time I did the 11 ft lbs then I used my trusty old deflection type torque wrench (it is reasonably accurate) to tighten an extra 90 degrees. Turns out, each one at a 90 degree turn equaled 30 ft lbs. Just to be sure, I verified that number with my calibrated click type torque wrench and it was the same. So there you have it, it was an extra 6 ft lbs more torque than the set rate of 24 lbs.
And I did reuse the cylinder head nuts and will again if I need to. Certainly, I can see not reusing rod bolts etc but head nuts, well I'm not getting it.

[Trackrash]

"Applies to the NEW CYLINDER HEAD NUTS".? What new cylinder head nuts?

[Alan L]

It looks like, from above there is a new part number for the head nuts - yellow. Must be different stretch material. But they say even if using these new angle torque nuts, it is OK to use ft/lb torque on them on an SC. Seems weird.
I have just checked my other manual which covers Carerra from 84-87. No mention of angle torque. So I think it has come in since they changed the head nuts. Only thing that makes any sense.
So Bruce - even if the years are advancing, your memory is fine, and you are up to date. Unlike the rest of us (and my 2 manuals). Think I would prefer to use 'old' nuts. That way I can check and retorque after assembly/break in, if I got motivated enough.
Regards
Alan

[HaroldMHedge]

Gordon,

If you wanted the final torque value when using the 90 degree method use a torque wrench with a dial indicator. Then you can see what the torque was at 90 degrees and use that value when re-checking the torque.

[Trackrash]

Originally Posted by HaroldMHedge

Gordon,

If you wanted the final torque value when using the 90 degree method use a torque wrench with a dial indicator. Then you can see what the torque was at 90 degrees and use that value when re-checking the torque.

Good point. I just finished checking mine for the 1K mile service. All tight at 25 ft. lbs.

FWIW, I don't see how the nut makes any difference. It's the stud that stretches. How will the nut change that? Does anyone have one of the yellow nuts we can look at?

Where are all the engineers when you need them?