Webcam, real or fake

[jgparker]

OK, I got what I thought was a smoking deal on a set of webcam early-S cams. They were unused and in the box, but a number of years old. After looking them over, the numbers stamped do not cross-reference to any web-cam numbers. ("RPM 149S", and a very faint "webcam"). So, are they something else? Here is a picture:

[Steve@Rennsport]

JP:

If you are doubt about those cams, you can always send them off to Web-Cam; they will index them and tell you what profile they have.

Thats the ONLY way you'll know for sure,...

[Wayne 962]

100% agreed with Steve - I would call them first...

-Wayne

[jgparker]

I just called, and Webcam did confirm that "149S" is their correct master cam number for their early 911S profile. They apparently stamp the master cam number, not the catalog part number onto their cams.

Thanks,

[jgparker]

I did a manual profile of the cam just to be sure, and yes it is an early S cam. This is how I did it. I did a graph on excel, but I don't know how to post that. PM me if you know how.

Thanks,

[Wayne 962]

Email me the spreadsheet - I will post it. Got more pics of that cam measurement? People might want to see that up close...

-Wayne

[jgparker]

I downloaded the image of the degree wheel from a Ducati web site and printed it on an 8.5" x 11" manila card-stock. Here is the URL:

http://www.machinerycleanery.com/DucatiTwinDisc.htm

I print the image so it was >8" across. The key is to align the disk to 0 degrees at the correct intake valve timing lift measurement, and to make sure the disk is centered accurately. I measured the lift every 5 degrees, for both the intake and exhaust. The crank must be at BDC during the process to avoid valve to piston contact.

I'll post some more pictures shortly. I plan to repeat on my CIS cams to compare them. I hope this is helpful.

[jgparker]

Here are some more pictures of my cam profiling procedure.



The dial indicator is mounted the same as for cam timing, but the chain housings are left off and the cam is installed loose.



Note my fancy Russian metric dial indicator, one rev for every mm, no conversion.



The degree wheel is clamped between the sprocket hub and the large cam nut.



The pointer is a piece of copper wire (Romex). Zero the degree wheel using the cam intake timing spec (5.2mm for S-cam).



Measure every 5 degrees. It is easier to do the "downhill" side of the profile backwards since the cam will try to run away from you after you go past the peak.



I used an old manila folder to print my degree wheel on.



Repeat on Exhaust side. It's hard to find a place to measure valve lift on the Exhaust side since the tool is designed for the Intake side.

Here are the results:

http://www.pelicanparts.com/temp/s-cam.xls

Note that the numbers on the degree wheel must be multiplied by two to get the degrees on the crank. I hope this was helpful. I'll also post my CIS profile when I'm done.

Thanks,

[jgparker]

As promised, here is the CIS cam profile, and a comparison to the early S Cams. Amazing how different they are.

http://www.lilyandgrace.com/misc/CIS-Cam.xls

[1980SC]

Which CIS cam is that ?

Rob
1980sc

[Wayne 962]

Hmm, I posted it on the server, did you get my email I sent you with the link?

-Wayne

[jgparker]

Rob,

The CIS cam is from a '76 911S. I should have mentioned that. Not the best of CIS cams, but an interesting comparison to the early s-cam.

Wayne,

Thanks for posting the original file. I did use your link in my previous post, but I just updated the file to include the CIS cam, and linked it on my PC rather than bothering you again.

Thanks,

[jgparker]

For onyone who can not open the spreadsheet, here are the images of the graphs:

[viejopatron]

Very interesting and I'm impressed with your craftsmanship. The only thing lacking is a calibration stamp for the Romex wire!

As I'm going to be installing Solex cams into a stroked 2,2 [to make a 2,4], I curious as to what your conclusion is? It appears that the S cam has a lot of overlap, does that concern you?

[jgparker]

Viejopatron, Thanks!

I believe the Solex cams are the very similar to early E-cams, which are great. That's what I have in my 2.2 and it's a fun combination. Less overlap, and slightly less peak power, but it idles nice, and is much more drivable. On my 2.8, I can tolerate a rough idle, and was more interested in peak power than drivability, so I went with the S-cams. Plus, it's the nostalgia thing for a Pseudo-RS type engine.

Thanks,