S Cams on a SC?
 

Are the early S cams the same profile for all years? I believe the profile is the same as the RS cams as well?

Would they fit in a '83 RoW SC? Thinking of ditching CIS to go EFI and cams can use an upgrade, ya? :-)

Thanks in advance!

Sprint.

You will need new pistons that have provisions for higher valve lift and overlap. you may be able to get your existing pistons modified if you have low miles on your engine. You also may need valve springs due to coil bind and seat preasure. It will definitely get you some pep...good luck!

Don't the early cams have 3 bearing journals and the SC has 4?

Good catch...Camgrinder has new billets that would work for that application and sound advise to boot.

There are better cam profiles for an EFI SC engine, and some of them will clear the factory pistons.
What type of powerband are you looking for? And does your budget include pistons etc?
I have billets camshafts for all years from 65 to 95.

3-bearing cams may be used in 4-bearing cam towers, but 4-bearing cams may NOT be used in the older 3-bearing cam towers,....:)

Hello, chums

I thought that 3 bearing cams cannot fit 4 bearing towers (47mm vs 49mm journals).

But cannot 3 bearing towers be bored to 49mm to take 4 bearing cams?

kind regards
David

As long as the journal sizes are the same, they will interchange (one way, as I outlined above). :)

If the 47mm cam carrier is drilled for oiling on all 4 journals, you should not install a 3 main journal camshaft. Luckily only the early 906 and RSR carriers were so drilled.
There are some late 2.7 carriers with the 4th journal, but they are not drilled. The 2.7 cis cams only have 3 main journals.
Some of my customers prefer these carriers and drill them for oiling. I have the early 47mm billets with 4 main journals.

All of the early 3 main cams are 47mm. The 83 SC is a 4 journal, 49mm cam carrier.

A quick note for people thinking about putting early cams and cam towers on late engines.
This is not a good idea.
The valve in the late heads are shorter so when you install an early cam on these heads you end up having to compensate for the short valves by running the valve adjuster way out or run lash caps.
This changes rocker geometry and puts a great deal of stress on the adjuster.
The later cams have a larger base circle so the short valves on 3.0 and larger were necessary.
Conversely if you put late cams and housing on early heads the valve adjusters stick way out and I have even seen them so far out that they hit the valve covers.
Answer:
Have DR cams grind the billet cams you need for your specific application.

BTW: Even when journal size is correct, if you put a three journal cam in a four journal housing that is drilled for a four journal cam you will have a huge oil pressure loss.
Example 906 cam housings (4 journal) with 911"S" cams. (3 journal)

Great thread!

Sincere thanks to all who help to educate us..

One point ..the later 49mm journal cams with the bigger base circle look to have a geometrical advantage for the more radical profiles..


I'd like to ask if there is a downside, provided of course the screws are shortened and do not foul?

Kind regards
David

The larger four journal cams have more bearing area and thus create more drag. This drag is responsible for increased friction and less horse power (not to mention heat) as a result.
Parasitic drag is a major limiting factor in Porsche engines when maximum horse power is the goal.

Good point, Henry.

I might groove the journals on the next motor anyway..

Has anyone tried this?

Thinking about it, it might be flexing.misalignment too...so the more journals the more binding..

Thinks of the Austin 7 Racing 2-bearing Crank!

Kind regards
David

Very interesting thread.
I need to think about this as I have just been at this stage. I have some Andial 4 bearing cams but the journals were the earlier 47mm and thus did not fit in the 4 bearing carriers on my SS 3.2 motor. We fitted 3 bearing carriers instead, so I need to check up on what Henry says!

Thanks

Alan.UK

We have early 47mm 4 journal cam housing for sale if that helps your project.
PM me for price.

Digging this old thread up as it's the same question I had.

I'm building a "wayne's picks 3.0" ditching the CIS, 79 heads, I'll get JE pistons and I have weber 40's, but I also have a nice set of '67 S cams sitting here.
Wayne book say's early S cams?
I'm on a bit of a budget so of course I was wondering if I can use these?
Or should I just flog them and get better?

You cannot run them. Wayne is suggesting a Early S profile on a late 4 journal cam. I personally would run a DC 40 "mod S" if I was inclined to have some new billets ground.

Sell the S cams to help pay for the new ones. Don't forget to look into the new type of piston J.E. is offering. They are up to 30 grams lighter. They are stronger, and the wristpins shave another 15 grams off of the old style. They are available for 95mm on up.