Camshaft recommendation for PMO'd 2.4S ? Options

[amallagh]

I've recently converted my 914-6 to a 2.4S spec engine with PMO 40 carbs.

The engine/heads are standard S spec but with 2.2S pistons giving about 9.3:1 compression rather and the std 8.5:1.

Can any one recommend a specific cam profile/supplier that is optimised for use on carbs with an S spec engine ?
If the std S cams from an MFI engine are considered to the the best for this application then I would be happy to hear your experiences.
I'm looking for a fast road cam to give me similar performance to the std S cams on MFI. The car is used on the road as well as for competition, so I need something smoothy and tractible at low RPM.

Regards
Andrew

[Phoenix-MN]

I think "Solex" was coined from the very ealy 911 engines cam spec that first used the Solex Carbs. The actual cam spec is somewhere between a "S" and a "E" grind. Someone can chime in if there is more to this.

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[ArtechnikA]

I think "Solex" was coined from the very ealy 911 engines cam spec that first used the Solex Carbs.

That is correct. The Solex (carbs) were spec'd for the original 2,0 911 (no-letters). The letters showed up around the time Porsche used the Webers to cure some driveability issues they eventually identified but the switch had been made. The Webers - originally made for an Alfa V6 (which is why the intake manifolds have slanty end-runners...) - gave improved tunability options and helped kneecap the T models so the top-of-the-line S was always faster (despite the T being lots lighter).

You really need all the numbers in any discussion of 911 camshafts, by which is meant Anderson's 911 Handboox and Frère's "911 Story" that have all the lift, duration, and lobe center data. Steve Weiner's Rennwerk site and WebCam's site also are great repositories of real data.

One thing to be aware of when comparing cam profiles - Porsche specifies timing at 0,1mm (near 'nuff 0.040"). The US 'standard' for cam timing is 0.050" so you need to read the small numbers and compare apples and oranges...

here's some cam data, copied by hand from WebCam, which I'm sure has already been posted to multiple threads by now...

CODE

Cam   intake        exhaust        lobe ctr
911T   216º .387" 207º .345    105º
911E   230º .408  222º .393      NA
911S   264º .450  236º .400    101º
Solex  244º .439  234º .406      97º
906    282º .465  252º .406      95º

the 906 kinda represents the "ultimate" small-bore 911 cam and didn't really start making power until 8000 rpm when used with 46mm Webers (and later MFI).

I can tell you from personal experience that E cams are very nice in a carbureted engine (BTDT).