Elephants Foot

[Ian France]

Hi



This is my first Porsche ( 1983 911SC) and after 3 years I`m trying to get a bit more involved
But---
During my first valve adjustment a couple of weeks back I managed to strip the thread on No 2 Exhaust adjustment screw!
I was able to lock the setting by adding a second nut and the engine is running ok but I would really like to replace the screw to undo the damage I`ve done.
I tried to loosen the locking nuts in the cam towers to remove the No 2 rocker shaft but they seem really tight though with engine still in the car and pre muffler in the way it is hard to get any leverage on the Allen keys .
Have an opportunity to get car on a lift and remove the muffler tomorrow but if the old nuts have been torqued in really tight am I likely to have a problem getting the shaft out even once I (hopefully) loosen the nuts? If so what sort of persuasion would you recommend?
Also am I right in assuming also better to then replace the shaft nuts and cones with new or am I likely to end with an oil leak anyway ?
Are the rubber seals special in some way or just standard o rings?What size?
Have read the Haynes and 101 projects section on rocker shafts plus all I could find on here including C.E.s very helpful tech article where using rubber seals not so recommended due difficulty installing however would really appreciate any additional recommendations on procedure/traps to avoid while removing and replacing the shaft.

P.S. Should the engine be at TDC for No2 throughout this?

Thanks
Ian

[Grady Clay]

Ian,

It is good to see you back on Pelican.
Your 911SC is looking great.

Please confirm that the elephant’s foot and/or the rocker arm threads are damaged.
It is possible that just the lock nut threads are damaged.
If it is just the nut, replacement is easy.



Yes, always have the engine at TDC compression #1 when doing anything with cams or the distributor.

If you need to remove the rocker arm, I agree, get the cat/pre-muffler out of the way.
Later, you also may be removing the left heat exchanger.

Try a rust solvent on the rocker arm shaft hardware.
Modify the Allen keys for best fit and leverage.

I recommend you have available a spare rocker arm, elephant’s foot, lock nut, rocker arm shaft, through bolt and cones.

When reassembling, you will need a modified Allen key and a very short, modified ¼”–drive, 5 mm Allen socket for a ¼“-drive torque wrench.



If you cannot remove the #2 exhaust rocker shaft or the hardware gets damaged, there is another way.

You can remove the left heat exchanger (with its attendant difficulties).
You can then attempt to remove the #3 exhaust rocker arm shaft.
If so, you can take a long drill and drill out the #2 exhaust rocker shaft bolt.
Keep in mind it is a hard bolt so you must be careful and use the correct drill bit and cutting oil.

Be very careful to not damage the rocker arm shaft bores in the cam housing.

New parts will fix the problem.


I hope this turns out easy.
Be very careful.
You don’t want a simple problem to become much more difficult.

Best,
Grady

[Ian France]

Thanks Grady
Now I feel much more comfortable - maybe (hopefully) not the biggest engineering problem but a big step for me and super happy to have your advice.
The old lock nut threads were pretty chewed up and the elephants food thread badly worn/virtually non existent where the lock nut should grip. (think maybe mine was just the last in a long series of twisted turns)
I split the old nut off and replaced it with a new nut with threads ground out clean as a spacer and threaded on a second new nut with good thread behind to grip the remaining good thread higher up the elephants foot screw so could lock the setting.
Not sure about the Rocker shaft nuts but both seemed real tight - mind I was concentrating more on the larger nut end and having now seen the new nut bolt ,shaft and cone set I assume (although realise is a two ended approach) I will need to get the smaller bolt end to turn first.
Good to know there is a poss 2nd approach if the shaft nuts are really stuck but I do hope I can avoid dropping the heat exchanger - those studs do not look inviting...
I have all the spares mentioned and intended to use all new regardless except perhaps the rocker arm (if internal thread ok) on logic all the other rocker arms and the cam shaft worn to same extent so maybe better not to have only one new if can avoid - is that ok logic or just penny pinching and I should replace the rocker arm anyway while I have the opportunity?
Also what do you think about those rubber seals? - I do not have the custom ones but if they are standard O rings If I have the size I should be able to find them here

Ian

[Grady Clay]

Originally Posted by Ian France

I have all the spares mentioned and intended to use all new regardless except perhaps the rocker arm (if internal thread ok) on logic all the other rocker arms and the cam shaft worn to same extent so maybe better not to have only one new if can avoid - is that ok logic or just penny pinching and I should replace the rocker arm anyway while I have the opportunity?


Also what do you think about those rubber seals? - I do not have the custom ones but if they are standard O rings If I have the size I should be able to find them here

I would use your old rocker arm if the threads are serviceable.
It is already ‘comfortable’ running against that cam lobe.


Perhaps someone can chime in on rocker arm shaft O-ring size and specifications.

I agree about heat exchanger hardware.
I’m a proponent of regular replacement of the nuts and gaskets just so you can easily fix problems like this.

I like your solution using a threadless nut as a spacer.
Very good – 10 points.

Best,
Grady

[Ian France]

Thanks again Grady
!0 points from you is a great and well timed confidence boost for tomorrow morning when I plan to dig into this

Best regards
Ian

[Ian France]

Hi Grady
With the pre Muffler out of the way I was able to get in there with a bit more length on the 5 mm side that and some WD40 got things going nicely.
Got the nut and bolt out completely but support itself was still quite reluctant to budge - eventually gave to hand pressure only and came out on the 8 mm side (eventually using small cut down plastic screwdriver handle in place of now probably permanently bent middle finger).
The bore was a little marked at each end so polished those up a bit with some household aluminum polish and a cotton polish pad on a dremel extension then cleaned up with a pull through rag.
I cut off the elephants foot end of the adjuster to avoid forcing the bad thread through the rocker arm which still looks good so re using.

The new support slipped in nicely however I read some references to the support fitting flush on the thin side but in Haynes if refers to inserting the support till you feel the recess with a feeler gage between rocker and tower then continue inserting another 1.5 mm.

The gage catches the recess on inside of thick side while support still just under 3.00 mm proud on thin side so another 1.5 mm ends with it just under 1.5 mm proud - Is that correct or should it indeed be flush? - seems strange Haynes would come up with the the feeler gage thing if its just "insert till flush with thick side"

Maybe it varies and I`m just being too precise here but do not know how tight the tolerances are and would greatly appreciate your advise again .
Thanks
Best regards
Ian

[Peter Seow]

Nice to see you back Ian. I am in half way through fixing the engine and at the same time, I am purchasing a 964 which in need of an engine rebuilt.