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Question for the Pros or Semi-Pros: How do YOU torque rocker shafts?

Well I am FINALLY buttoning up the 901/05 engine for my car, it's a long story, but bascially the restoration of THE CAR got in the way of finishing the engine. . .

I installed the rockers today, put the M5 hex wrenching feature on the inboard side so I can get the rockers out with the motor in the car in an emergency. (I can imagine dropping the engine except in an emergency) Put the M5 hex on the THIN side of the inner rocker. All good.

Went to torque them down and realized that my 3/8" drive torque wrench, adapter to 1/4" drive and 1/4" drive M5 hex driver will not all fit in the opening between rockers. I did the leftmost one by using a series of long extensions, but you can only do one that way. Did the others by holding an M5 allen key and turning the M8 hex end which you aren't supposed to do.

(The friction on the M8 hex end of the rocker shaft is enough to make the reading unreliable, and they stick in the bore. I knew this from Wayne's book and listening to the experts but I ended up stripping one of them out anyway. Porsche LOVES to make the internal wrenching feature coaxial with the fastener, just like in the head studs or heat exchanger studs. Must be something in the water.)

How do those of you who make a living building Porsche engines torque the rocker shafts? I guess use a 1/4" torque wrench?

Bonus question: how do you get the rocker shafts out of the bores if they won't slide out easily? I am using the RSR seals- some of the shafts slide in smoothly, some need a little more effort. That is with ZERO preload on the bolt so the ends can't be expanding at all.

THANKS in advance for any time taken to reply. . . . I can see the light at the end of the tunnel . . .is that a train whistle I hear?
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Old 03-26-2011, 05:25 PM
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If you polish your shaft it always slides in much easier. I have never put a torque wrench on a rocker shaft. What should the torque be? But there is one direction they go in which makes it much easier should you have to remove them.
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Old 03-26-2011, 06:59 PM
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torque

I use a 1/4 drive ratcheting torq. with a wurth 5mm allen, set it at 175 inch # good to go

Mike Bruns JBRacing.com
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Old 03-26-2011, 07:17 PM
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Hi 304065,

The original Stahlwille Manoskop works nicely, if you don't mind working in centimeter-kilopond. At least there's no math to do. It's 3/8" drive, but no ratcheting head, so fits inside the opening with room to spare...



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Old 03-26-2011, 09:08 PM
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THANKS everyone for the advice.

Browsing the Hazet catalog, it appears there is an adapter that will reduce the 3/8" square drive of my Stahlwille torque wrench down to 1/4"- I can then use an M5 hex driver. I guess I could fab this out of bar stock with a file, just like in shop class!



Those vintage Manoskop photos are cool and my spec books are already in meter-kilopond anyway!
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Old 03-27-2011, 03:34 AM
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John,
I use a 12" extension bar on my 3/8" torque wrench for the farthest ones, a 6" extension for the middle ones, and no extension for the nearest ones.

See : Charts

I first do the far ones in a row, then the middle, then the nearest. An extension bar just passes through the bores for the rocker shafts.

For no extension bar, I use 18 lb.-ft. and no RSR seals if the cam tower bores are clean and nice.
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Old 03-28-2011, 09:58 AM
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Do not over torque them. The shop who built my engine did this several times, and my motor kept throwing rocker arms
Old 03-28-2011, 02:02 PM
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OK

Made some progress today using my Stahlwille 730N Manoskop (that's an adjustable torque wrench folks!)

The insert I have does not ratchet- it just has a 3/8" recess in it, and you use a square bit like the 3/8" in the photo I posted above. I don't have a 3/8" to 1/4" adapter for it, and it's just as well, because the Stahlwille 1/4" drive M5 hex key I have is about 55mm length overall itself.

Here's the deal: the size of the hole you have to fit the torque wrench into is exactly 55mm. The regular hex bits you buy at the FLAPS are 3/8" drive, and the one I have is 51mm length overall. So together with the head of the torque wrench, it measures 64.73mm long. Too big to fit in the hole.

OK, so I need a 3/8" drive M5 hex key that is only 40mm long at the absolute maximum. I think the thing to do is to buy a short one and file (not grind) it down. These are about seven bucks from the usual sources (I'm not filing down a HAZET!) The one I am thinking of, a Proto, has a replaceable bit.

For holding the M8 side, a hex key that has been filed down a bit is a good idea. The goal is to square the end, the chamfer or "broken edge" on the tools as they come from the manufacturer is dangerous, because it positions the bit shallower in the internal wrenching feature, making it more likely that it will pull out while you are using it and strip the internal wrenching feature! So file it.

And in the "confessions of stupidity" department I managed to break a rocker shaft and strip a pinch bolt today. Remember how the torque wrench doesn't ratchet? Well, I had it positioned the wrong way round, with the arrow pointing in the wrong direction, when I was torquing down the #3 intake rocker! I kept wondering, "wow, this pinch bolt is really elongating, I better stop!" When all of a sudden I hear this barely audible, "PINK" sound from the cam box.

"Himmel-herrgott-scheissklump-verrekts" or something like the official Factory swear went through my mind! Went to back off the pinch bolt and stripped the inhex like butter.

I then spent the better part of the next hour stuffing the plug hole with a greased rag to both block the chips and catch them, then drilling out the pinch bolt head with a progressively larger series of bits. When the bolt head finally wore away to the point where it failed, the pinch bolt shot out the other side and hit the back of the chain box! Vacuumed all the chips and used a magnet to get the ones I missed.

Then I found half the rocker shaft stuck in the rocker bushing. Heated it up and pressed it out, no apparent damage.

What a day! I am using the RSR seals on all the shafts, after the treatment of this rocker shaft bore, I'm sure hoping I don't get a leak. If it leaks I'll just tear it down and replace the cam box, preferably with one from an engine that has never been rebuilt by an amateur like me!

Do I feel better having confessed my stupidity and lack of experience? Not really.
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Old 04-02-2011, 05:13 PM
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You must have had a pretty good arm to snap that bolt! I just tested one to 35lbs and still holding.
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Old 04-02-2011, 06:25 PM
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When the shafts are good you only have to hold the the non torquing nut till it comes up snug and then it quits spinning....if the nut doesn't stop spinning the shaft is no good and a new one is needed. Then I torque to factory specs.

I know, this is heresy.....but I never have had a lick of problems. I had a few extra new shafts standing by and used 2 during 2 builds, IIRC. It is all laid out in B Andersons book. I'm not even semi pro, but I can read & follow instructions. I also have the ability to see how the shafts do their job and why they might not....no rocket science there.

1/4 inch drive inch pound torque wrench worked for me.
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Old 04-02-2011, 07:08 PM
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Quote:
Originally Posted by 304065 View Post
Here's the deal: the size of the hole you have to fit the torque wrench into is exactly 55mm. The regular hex bits you buy at the FLAPS are 3/8" drive, and the one I have is 51mm length overall. So together with the head of the torque wrench, it measures 64.73mm long. Too big to fit in the hole. OK, so I need a 3/8" drive M5 hex key that is only 40mm long at the absolute maximum.
John,

The original Porsche 5mm tool, P211, was a 3/8" drive Stahlwille Inhex cut down to 37mm in length. Mine has seen better days, so I cut a Snap-On FAM5A down to 35mm, and could get it to 32mm if necessary. The head of my Stahlwille torque wrench is 10mm.

The Hazet 6413-2 adapter you pictured above is available from Samstag Sales for about $14, the 6413-3 even less. Scroll down to the bottom of their Hazet page.

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Old 04-03-2011, 12:15 AM
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Quote:
Originally Posted by J P Stein View Post
It is all laid out in B Andersons book. I'm not even semi pro, but I can read & follow instructions. I also have the ability to see how the shafts do their job and why they might not....no rocket science there.
JP,

I have tremendous respect for Bruce Anderson, but his references to rocker shaft bolts were incorrect, as are many manuals. Porsche went from a 6mm to 7mm bolt in 1967, so any book or table that notes "M6" is obsolete, including Porsche's own Specs booklets. An M7, 12K/12.9 grade screw/bolt should safely accept 25 Nm / 18 lb-ft of torque (per BMW N 600 02.0, DIN 267). I understand there are other factors involved, but I believe in this case such torque is safe and necessary. I've been using 240 cmkp, a bit over 17 lb-ft, on new M7 bolts.



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Old 04-03-2011, 01:09 AM
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Old shot from the teardown- I had both kinds installed!
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Old 04-03-2011, 03:30 AM
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The pinch bolt assembly expands the shaft. The chamfer on the ends of the shaft has a sharp (un-broken) edge at the OD. This sharp in necessary to "bite" into the shaft bores in the softer cam tower to seal it and to prevent movement. This sharp edge gets dulled with excessive use and/or somebody with an abrasive "cleaning" the shaft. I believe this leads to leakage & "walking" of the shafts in use. Shafts are cheap. With the proper torque, this "pressing" action will not make a permanent dent in the bore. So, enough torque....but not too much, IMO. My 14 ft/lbs works just fine.....with good shafts, and more torque is not necessary.....tho I doubt another 3 ft/lbs will do any harm.

This is my opinion, but if ya'll don't like it...I have others.
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Last edited by J P Stein; 04-03-2011 at 07:08 AM..
Old 04-03-2011, 07:05 AM
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Wrapping this up- M5 Hex bits are very inexpensive. But if you order the Danaher/KD tools/Allen part, you get one that is too long.

It's not a question of just grinding down the end, because the bit is tapered.

You must drive the bit out of the socket with a punch, cut off the back of the bit with a dremel, taking care that you do not overheat the part ( I kept a wet rag handy and would dremel a bit, then cool the part with the wet rag).

Once the bit is cut down, you press it back into the socket. Took about ten minutes:





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Old 06-19-2011, 03:17 AM
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After I redid my engine...months..maybe longer....I was doing a valve adj.
Noticed a rockershaft had worked its way out of its home..
After some talk on the board here Jn Walker recommended a much higher torq then the books recommended.
I can not remember the Torq...but I was dam sure I was going to break the bolts....never did..never more a problem either!
OHH and I put in those little RSR seals too....most beneficial
Old 06-23-2011, 08:38 PM
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"mmmp". That's about right.

"hrrrrgh" is too much.

That's how I do it. Works well!
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Old 06-24-2011, 12:23 PM
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Like John W I torque them a little extra, 3-5lbs IIRC, but don't have the spec in front of me.

I put the bolts in with the heads facing the flywheel on both sides, not worrying about servicing a rocker while the motor is in the car..... then use a series of extensions, same as Scott above, to torque each one....

Never had an issue with one.

Cheers
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Old 06-24-2011, 09:35 PM
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