906 cams Q - compatibility with 2.0s 67/68 carbs.

[gilbert911]

factory 906 cams in - factory 2.0s cams out.
Will it work retaining std 2.0s heads, P&B's?, rods?
Can the cams work in the std spray bar towers?

Thanks for all advise

[edmayo]

I've not done it, but I don't see why the spray bar won't work. What you will need to check however is the piston valve clearance and the diameter of the valve compared to the valve pocket. I'd suggest doing a trial assembly with clay checking of the valve piston interface.

[BURN-BROS]

Hi Gilbert,

The heads would need to be ported to effectively use those cams.

With ARP rod bolts you could use the stock rods provided you keep the rpms under 7800 rpm. They can see 8200 rpms, but I would be concerned about failure at that point.

If it is a centerlube set of cams then you will need to plug the nose of the cam to prevent pressure loss.

Spray bar cam towers are recommended and centerlube/spraybar would be ideal.

The stock pistons will not work and the compression is quite low for such a big cam. A set of 69S pistons may give you the clearance but clearance would definitely be checked with clay. 906 pistons may very well be required.

The carburetors are too small, but can be made to work ok with larger venturies.


A better cam for what you have would be a Mod S with mild portwork. The Mod S can make 40 more HP @ 4500 rpm than 906 cams, which really do not start working untll 5000-5500 rpm.

[gilbert911]

Aaron, Ed
Thanks for taking the time to reply - appreciated.
My question was what would happen if I swapped out the cams. My GOAL is actually to try and get some 46IDA's on tall manifolds to work on a 2.0s 67/68 engine.
I figured I would need the 906 cam to cope. But the knock on changes seem significant.
So my goal - what would be the implications of running the 46's on an otherwise stock 2.0s engine?

Thank-you

[andyjboy]

I think that they would be overkill - in addition 906/911R tall manifolds have 38mm lower ID to match the inlet ports on those engines so wouldn't work with a stock 2.0S engine.

I have been speaking with Mark Allen @ Vintage Excellence about the repro tall manifolds that he has advertised on this board but they are some way from 'production' & SG Racing in Belgium (who had been offering similar manifolds for a few years) seem to have disappeared (certainly their website is now inaccessible).