82Porsche928

It says 93 octane in red on the label..

Rob Edwards

Brendan, they're S4 cores, stamped with webcam 505 (exhaust) and 610 (intake) grind numbers. Can't find any info on what those grinds are, even in the wayback machine to 2002:

https://web.archive.org/web/20020602...camshafts.com/

Never been run:






Intake nose, dated 7-99 (?)



The coating isn't very robust- fingernail scratch:

BC

YOur cam machine sounds intriguing. I have a good friend who is good with hardware-software interfaces.

Those S4 cam cores - also intriguing. Welded? But to what amount? Looks pointy like the Elgin grinds.

I will be taking off the cam covers from the GT and seeing how "worn" they may be, if at all. Always tempting to run something else and put them on shelf for preservation. It will be more and more difficult to find people to do small runs of bespoke grinds for... even big money.

Speaking of cams, etc - has anyone heard from Simard?

Strosek Ultra

The Web-Cam #505 grind is 200 dgs @ .050" and has a lift of .352". Cannot find any data on the #610 but both are very mild cams. Grind #505 probably is identical to the stock 928S4 intake grind. The coating is a dry film lube (probably sprayed on) for lubrication at the initial start up. This is how I figure out the cam profile. The chart is showing the 928S4 intake profile.
Åke

ptuomov

Rob, do you have a photo of the 610 stamping?

Rob Edwards

Yep, 2nd to last pic in my post above.

Here it is again, it's not very evenly stamped:

ptuomov

I'm sorry but I can't see 610 anywhere in that picture. I see 7, 10, and 99. Where's the 610?

Rob Edwards

It's poorly stamped. Here's the pic with different contrast settings, annotated. I'll take another in bright sunshine if I ever get out of here tonight. Ignore the 'a' in 10a, typo on my part.

ptuomov

Thanks. Since you have two intake cams, perhaps the other cam has a more legible stamping for the Webcam lobe number. It'd be interesting to figure out what the mystery intake lobe is.

As Ake identified, the exhaust seems to be a lobe that's still used as the intake lobe in 16V Mazda Miata. The catalog notation is slightly confusing because they also sell the same profile with the nose circle "spread out" 2*2.5 degrees for increased duration.

Rob Edwards

Hot off the camera- here's the other (1-4) intake, better '610' stamping.

Quick and dirty with my calipers suggests 8.7 mm of lift, including the dry film coating.

Rob Edwards

Looking through paperwork that came with the Zombie, I found a sheet of specs from Elgin in March 1996 with a couple of different grinds on it. Looks like the Thompson grind essentially matches the factory GT profile in lift and duration just a little shy of GT numbers. No idea whether they're welded and reground or just base circle reduced, nor is there data on whether the LSAs were altered. Given the more aggressive grinds on the list, I'd guess they're all welded and reground.

Anyway, here are the numbers with the stock S3, S4 and GT for comparison:

Strosek Ultra

The camshaft stamped WEB 505 is also stamped 274.00 which is a GTS exhaust cam core. I do not have a lift chart of the GTS exhaust but the lift and duration is almost exactly S4 intake. The WEB 610 is also stamped 7.99 which tells us the cam was made by WEB in July 1999. Isn´t this set of cams that never has been run a set that has been fixed and repaired by WEB-Cam? Looking at the cams the profiles all look like stock cams.
Åke

ptuomov

From memory, I recall that S4 exhausts are stamped 273.00 and 274.00 while GTS exhausts are stamped 273.03 and 274.03. So I'd say these are on S4 cores. The Webcam #505 profile is very close to the 928 GT exhaust profile (and also to S4 intake as Ake says), so it's a sensible exhaust cam for an engine that uses the stock 928 MAF and intake. Too small for Ake, of course! ;-) If the S4 exhaust LCA was retained, then it's 8 degrees less than the GT exhaust, resulting in 4 degrees lower LSA and more overlap. Without any evidence, I'd guess that if you'd swap that exhaust cam to a GT you'd get more mid-range torque, a lopey idle, and a bit higher emissions.

traxtar928

So, what does all of this translate to? The Thompson Cam grind basically means that I have GT cams in my S4. Sound like a good summary?

Since buying the car, I've added an X-Pipe and RMB... perhaps it would be beneficial to get the chips re-programmed?

Rob Edwards

Essentially GT cams, yes. I would dump the old chips (would be interesting to send them to PorKen to get a read on what the maps look like...), get a pair of PEM chips from John Speake and hook up with Sean there in DFW and take advantage of the cams and exhaust by Sharktuning the car.