E-Grind cam or are these something else

[Brent Lineker]

E-Grind cam specifications

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I just got back from machine shop to get my specifications for my cams.I had e cams put in for a 2.7 rebuild with mahle RS 90 mm p&c's webers,ssi's and sport exhaust.The specifications are as follows.These were reground from my CIS cams
-Intake duration 219 at .05 valve lift .420
-Exhaust duration 212 at .05 valve lift ..396
I can't find these specifications on any chart.Does anyone know if these are indeed e cams or in fact something milder

[RSstop]

Brent,
If they are reground from CIS cams, they probably retained the CIS lobe centers. Lobe seperation is a few degrees more than original E grind. I'll look for some conversion charts I had for Porsche cams. They could be E grind lift and duration with less overlap.
Lyn

[Brent Lineker]

Thanks Lyn,I appreciate it..Brent

[jasam]

John (Camgrinder) is the macro-master-wizard of the camshafts... contact him for info, he´s been really helpful...

Cheers

[RSstop]

Brent,
Check out John Dougherty's web site. http://www.drcamshafts.com/911profilesprint.htm

It lists E spec:
Intake duration 230 at .05 valve lift .405
Exhaust duration 222 at .05 valve lift ..393
Yours are close to "E" lift an duration.

The spec you don't mention is Centerline or Lobe centers, which can alter the torque curve. The CIS injection couldn't tolerate high overlap, thus 110 degree lobe centers.
Lyn

[2.70Racer]

Brent,
US cam grinders use .050" opening and closing for specifications.
Porsche quotes their cams with a 1.0mm opening and closing.
1.0mm is quoted as .040" in the US.
This means cams using spec's with .050" will show less duration than a European spec using 1.0mm (.040").
I suspect they all like the confusion.
E cams and Solex cams at 1.0mm run 248 degree intake duration.
Using .050" the spec for the same cam is 242 degrees of duration.
Thanks to John dougherty for showing it both ways.
Another bit of useless trivia, Early Porsche cams were specified at absolute opening.
This made the early cams look to have much more duration.
Somewhere in the early 70's they changed to the .040" standard.
You need a scorecard to actually compare cam spec's.

[RoninLB]

Originally Posted by 2.70Racer

Another bit of useless trivia, Early Porsche cams were specified at absolute opening.
This made the early cams look to have much more duration.
Somewhere in the early 70's they changed to the .040" standard.
You need a scorecard to actually compare cam spec's.

Great info. That probably explains different 1969 and 1971 E-cam numbers in P text... thx

did the info come from John Dougherty ?

[2.70Racer]

Ronin LB,

Paul Frere's book "Porsche 911 Story" is my source.
On page 83 he is discussing the change over from 3.0 to 3.2 engines.
At the bottom of page 81, with the early method of using the absolute intake valve opening and closing he quoted opening at 27* BTDC, closing at 73* ABDC.
At the top of page 83 he requoted the same cams using the 1.0mm opening criteria. The spec became the intake opened at 4* BTDC and closed at 50* ABDC.
A difference of 46* with the different specification.
Also in the appendix B page 355 about mid page, he shows the C2 and C4 specs with a note, "with 1.0 mm check clearance."
All prior specifications used the zero opening, which effectively added 23* to the intake opening and 23* to the closing, for a total of 46 degrees.
The same exact cams, just quoted differently.
To correct myself, the change in quoted spec's, at least by Paul Frere came in the late '70's, not in the early '70's.
From what I can tell, Bruce Anderson in his "Porsche 911 Performance Handbook", used the 1.0 mm standard for all of the cams he specified.
Confusion seems to reign when reading Porsche cam spec's.
Like I said, I believe the cam people like it that way.