Cam Tower Help 2.2T

[bobolsn]

I am in the process of restoring my 71 911T. It has been a long time, but I am now making some progress. I am now split between the body (rust primarily), suspension (bushings, paint, shocks/struts) and the engine. The tranny, body paint, and interior will be scheduled (LOL) when one of the former is complete. I have been reading the forum and occasionally provide a response to very easy questions (i.e. what part is on a 70 or 71 911?). The forum has gotten me this far by searching and reading and I am very appreciative.

Anyway, the question at hand has to do with the engine, specifically the cam towers and the rocker arm shafts. As a result of my reading, I had to back track and will have to put some Curil T on the copper cylinder gaskets. B. Anderson puts on them on dry, where as most others use a light coat of a sealant and I don’t want them to leak. The cylinders and heads are on, but not torqued. As I was preparing to put the cam towers on the heads, I checked to make sure I could get the rocker shafts into the cam tower housings. Eight (8) of the 12 shafts would slip in snuggly, but the other 4 would not go in. I do not want to tap or pound them in for fear of ruining the shafts, cam bores and/or the rocker bushings.

Some diagnostic notes:

1- I labeled all the rocker components (1-exh, 2- Int, etc.) as they were removed
2- all the shafts will go into the rocker arms
3- the shafts that will not go into the cam housing are 1-exh, 5-int, 6-int and 6-ext
4- Say 4-int shaft which will go into the appropriate cam housing will not go into 6-exh housing
5- tried to clean the shaft and housing with acetone to get any varnish off with no luck
6- could not feel a burr or lip in the housing
7- put the shafts on a flat surface and it does not appear that the shaft ends have expanded
8- the shaft bolt and nut are out of the shaft during installation
9 – the cam towers have been sitting indoors on a shelf, climate controlled area
10- the rocker components have been stored in baggies with an oily paper towel
11- there is no observed oxidation on the cam towers

The question is what next?

Have the shafts and cam bores professionally polished?
Have the cam bores honed?
Buy new shafts? (they still may not go into the bore)

Any advice will be appreciated. I am stuck now on this engine thread, so am painting the suspension and touching up the under belly and the engine bay. I have read posts from some very experienced builders on the forum, so I suspect they (you) have been here before.

Here are a couple of pictures I took of the cams and rocker shafts. May be someone can see some that I can’t.












Thanks

Bob

[Flat6pac]

Put some lube on the shafts and they ll go in. They are oil seals and need to be a tight fit.
Bruce

[bobolsn]

I thought I had tried a little lube, but I tried again. The same shafts can not go all the way in. A couple started, but stopped near the seal ring. The others could snuggly go into the cam bore. I think I could even successfully get the seals into the bores.

Any other suggestions?

Bob

[Heinz911]

In my engine I had a shaft that had a crack on the edge of the groove. It was very hard to see without the bolt compressing the shaft. If you are sure that you don't have a crack you can use a 13/14 mm sprocket on an extension shaft and gently drive it in with a mallet. If you are using the RSR seals, they could also give a little extra resistance.

[JFairman]

I've carefully used an L shaped allen head wrench as a little pry bar lever to push them in. I think it was an 8mm wrench.

Then when the shaft is in far enough that there isn't anything to lever the allen wrench against I put a small 3/8" drive socket under the 90 degree bend of the allen wrench between it and the cam housing as needed until the rocker shaft is pressed in to the right depth.

It's a little hard for me to describe it but it worked fine for me and I didn't scratch, mark, or harm anything.

If you're using the flat oring rubber oil seals in the grooves of the rocker shafts they will get torn or cut off around the outer edges a little as they get pushed into the bores.
Then they won't work as oil seals anymore and are a waste of money and you may as well just not use them.

To keep that from happening first take a little 400 or 600 grit wet or dry sandpaper and carefully and lightly smooth down the sharp edge of the rocker arm shaft bores so the rubber oil seals will compress inward a little and slide past the edge with out being pinched and torn as the rocker shaft is sliding in.
A little motor oil on the rocker shaft and oil seal helps lubricate them as they slide into the cam tower bores and if the seal isn't torn while going in they should work.

Most 911 engine builders I know don't use those overpriced rocker shaft oil seals and they install them dry.

[chris_seven]

The problem is that the tolerance specified by Porsche is very close indeed

In the limit the minimum bore size specified for the carrier is 18.00mm and the maximum shaft diameter is also specified at 18.00mm.

This means if you have the situation where you try to fit the largest shaft into the smallest bore they just wont fit.

Oil won't help if this is the cause and I am not keen on forcing them into place or trying to polish them to a correct size.


It may be worth trying to mismatch them to the carrier as once clamped they shouldn't move so I see no reason why the shafts need to be re-fitted to the original bore.

can you warm the carrier slightly as a warm workshop would help a little.

[bobolsn]

I do really appreciate suggestions. I am glad that I am not the only one who has this experience.

To respond to a couple of the suggestions. I have tried other shafts in the "no-go" bores without success. It appears that it has something to do with the 4bores. I did try to freeze the shaft, but that did not help. A note, it is getting cool in GA and the cams (in the garage) are a bit cooler. I tried the shafts a little while ago and No. 6 exhaust will go a little further in, but only so far.

I believe I will try a little more cleaning/polishing before I use JFs pry technique. May be the 1200 wet/dry paper that JF suggested.

Again many thanks

I will post my progress/results.

Bob

[bobolsn]

Well after many unsuccessful attempts I bit the bullet and sent the cam towers and components to Ollie's. The bores and the shafts were polished and the rocker arms were fitted with new bushings. The rock faces were also reground. Now I feel confident in the cams, unless I do something stupid.

Now on to the next reassembly issue.

Thanks again for your responses.

Bob