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

[amallagh]

Great info, thankyou.

So is the Solex cam specifically optimised for use with Webers (PMOs) as well ?
I see the cam data posted above shows the progressively increased duration and lift from the T to the E to the S cam as you would expect.
The Solex grind however breaks this linear trend of these 3 cams with intake duration and lift sitting nicely between the E and S cam specs, but the exhaust duration is similar to the S and the lift is even greater. I see the lobe centres are also closer than on the S indicating more overlap. So the Solex is 'hotter' in some respects and 'milder' in others compared to the S cam.

Are these the characteristics that a Weber fuel system needs for peak performance ?
If the S cams make about 195bhp, and the E cams about 165bhp on a 2.4, then how much bhp would you expect with the Solex cams on Webers or PMOs ?

If the Solex cam is ideal for a PMO set up with S heads then the next question if where to I get a pair at a reasonable price ?

This has been really useful.

[ArtechnikA]

So is the Solex cam specifically optimised for use with Webers (PMOs) as well ?

it's reasonable to assume that the only 'optimised' combinations are what came from the factory. You should expect to do some tuning with whatever cams you get, which can be great fun, especially if you have a chassis dyno... "Let's see - the engins is running a bit rich above 5500 rpm - do I fit a smaller main or a bigger air correction?" The only real answer is you try both and see which the engine likes better. Jets are available. Emulsion tubes, which (help) modulate the transition between the idle circult and the mains less so.

I see the cam data posted above shows the progressively increased duration and lift from the T to the E to the S cam as you would expect.
The Solex grind however breaks this linear trend of these 3 cams with intake duration and lift sitting nicely between the E and S cam specs, but the exhaust duration is similar to the S and the lift is even greater. I see the lobe centres are also closer than on the S indicating more overlap. So the Solex is 'hotter' in some respects and 'milder' in others compared to the S cam.

You also have to factor in stuff like what pistons were available at the times and what valves the respective engines used to determine how much lift could be used without 'contact.'

Are these the characteristics that a Weber fuel system needs for peak performance ?

All those cams were good at what they were good at and less good at others. E was a good compromise. S has good peak power, crappy fuel economy, iffy driveability, and will foul plugs in light driving if jetted for peak power. it's all tradeoffs. You can also tweak things A LITTLE by advancing and retarding the cams a bit, a game even the factory played from time to time, but these engines do not respond to that trick like some do. Still, if you make a guess and decide you only missed what you wanted by a little, it's a cheap and easy thing to try.

If the S cams make about 195bhp, and the E cams about 165bhp on a 2.4, then how much bhp would you expect with the Solex cams on Webers or PMOs ?

at what rpm? with what venturiis? and what exhaust? You can speculate endlessly, and the fact is that all this stuff is more than a little nonlinear and the only real answer is to build up the engine and ask it, on a dyno. This more than anything is where the 'real' engine builders earn their big bucks.

If the Solex cam is ideal for a PMO set up with S heads then the next question if where to I get a pair at a reasonable price ?

you can't and you wouldn't want them if you could find them. Real Solex cams date from the days when Porsche was oiling cams by sending pressurised oil through a drilling in the center of the cam and letting it out through port in the base circle of the lobes as well as the bearing journals.

What you do is get a cam grinder (like WebCam) to grind that profile on either new billet or rewelded core cams. WebCam has been doing that game since the 50's and it's a trusted, reliable method. There are other grinders too, I've just researched WebCam a bit more than I have the others.

This has been really useful.

It's all a part of doing the homework.