906 cams and lightened flywheel questions

[Sixtyseven911]

Pulling apart the old motor from the 67 today. Found a pair of center lube 906 cams and a lightened flywheel. The heads are opened up from what I can see on the top side, as well, but that'll be another topic.

question is how to proceed further on removing the cams and ultimately the chain boxes. I have the nuts, gears, and 3 bolts out of the end of the cam, but not sure where to go next. BTW...thanks to the good guys Jeremy and Peter over at TRE for getting those pesky little 906 cam nuts off....smaller than standard size...41.5 mm!! Who makes something 41.5 mm?!

Any help appreciated.

Also, any help in identifying the lightened flywheel would be great. I don't see any numbers or anything, but thought it may be cool if someone knew who made it or if it was a factory unit.

[Jon B]

I have the nuts, gears, and 3 bolts out of the end of the cam, but not sure where to go next. BTW...thanks to the good guys Jeremy and Peter over at TRE for getting those pesky little 906 cam nuts off....smaller than standard size...41.5 mm!!
Who makes something 41.5 mm?!

You need to remove all the rockers before pulling the cams, easier to do with the chains still in place. If you've already done this, you didn't mention it.

The 906 cam nuts are 41mm ATF, which is actually a common metric size.
The factory tool to remove & re-torque the 41mm 906 cam nuts was P139, pictured below (right) with the standard 46mm cam nut tool, P203 (left)...





Jon B.
Vista, CA

[Sixtyseven911]

Great info Jon. Thanks. No I had not removed the rockers but I had backed the adjusters off. I'll take the rockers out as you indicate. Anything after that?

[Jon B]

No, once the rockers are removed you can pull the cams out.
Keep track of which rockers & shafts went where. Check to be sure all the rockers and idler arms are the type with bronze bushings.

Jon B.
Vista, CA

[Sixtyseven911]

Ok. I'll number the rockers and look for the bronze bushings.
The center lube cams were not set up with the exterior oiler parts for lubrication. Is there anything different about the chain boxes or cam towers for these cams?

[chris_seven]

I need to manufacture some cam nuts to suit a 906 cam and I have previously learnt that they are 41mm AF.

I have not managed to find any positive data with regard to thread diameter or pitch.

Would you have the time to measure the OD of the threads on the cam and the pitch?

We also need to make some 'billet' 906 cams so I would be very grateful if you could make this measurement.


I would also be very interested to know if the engine has adjustable rockers?

I thought that the 906 used a 'solid' rocker with a lash cap for adjusting clearance.

The 906 Rocker also had a longer heel to do with the increase in lift and I have been told, but have no direct experience, that using standard rockers can be an issue and that the heel can wear at one of the edges when used with these cams.

We have recently made some new adjustable forged rockers as Appendix K has specifically banned the use of solid rockers in Period F race cars and we also don't believe that CNC machined parts would be acceptable.

These rockers have had the length of the heel pad increased to be identical to the 906 Rocker.

We have paid great attention to the metallurgy, heat treatment and surface condition.



The solid rockers had no bush and ran directly on a surface treated rocker shaft and we have fitted a standard Glyco bush as used in most 911 Rockers.

[Mr9146]

Just an FYI: Msroadrace appears to sell the proper 906 cam nuts on his eBay site, albeit remanufactured in 46mm for use with standard crow foot.

That's from memory...

[chris_seven]

I have seen the MS Road race listing and Rose Passion in France have genuine 41mm AF RSR Nuts in stock for 30 Euros each but we need to make the nuts to match up to some adjustable chain wheels we have been making using an Aluminium Sprocket, Titanium Hub and Titanium Cam nuts.

[Jon B]

The center lube cams were not set up with the exterior oiler parts for lubrication. Is there anything different about the chain boxes or cam towers for these cams?

Those are not '67 chain housings (original to your '67 car), so it's hard to say what you have without more information or pictures. Those cams can be used in center-lube or spray bar set-ups.

Chris, he mentioned that he had "backed the adjusters off", so I assume that he has adjustable rockers.

Jon B.
Vista, CA

[M_deJong]

No, once the rockers are removed you can pull the cams out.
Keep track of which rockers & shafts went where. Check to be sure all the rockers and idler arms are the type with bronze bushings.

Jon B.
Vista, CA

I suggest you remove the Woodruff key, spacers, thrust washer and round aluminum plate before you try to pull the cam out.