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Early vs late E cams

I just compared 2.4 E cams to 2.0 E cams using a dial indicator and rough marks on the pulley....
They seem to be the same.
The cams are original to my 69E built in Oct,'68. It looks like there is no difference in early or late E cams.
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Old 07-27-2004, 08:39 AM
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Thanks for the clarification Ed. Now we know -- I'll adjust my data.

- John
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Old 07-27-2004, 10:36 AM
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Live and learn. There are a couple of references that have this wrong then. Thanks for the info.

JP
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Old 07-27-2004, 12:40 PM
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I can always make you a "late" E cam...
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Old 07-27-2004, 06:37 PM
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When I really studied cam data from Paul Frere's book "Porsche 911 Story" and compared to Bruce Anderson's book "Porsche 911 Performance Handbook" I noticed the specs didn't always match.
Upon closer reading Frere's book he changes the criteria for cam specs at page 83. On page 81 he shows the intake cam timing for the 3.2 motor as open 27 degrees btdc/ closes at 73 degrees abdc. This is the old way of measuring cams. It is done with the normal 0.1mm valve clearance and shows the valve opening when it just begins to move.
On page 83 he shows the same cam timing with "zero clearance and when the lift has reached 1.00 mm" to reflect Porsche workshop operation. With the new spec at 1.00 mm lift the same cam becomes intake open at 4 degrees btdc/ close at 50 degrees abdc. So you can see with the two different ways of measuring the cams gives us two distinctly different sets of numbers for the same cam.
Frere, from page 83 on, shows cam timing numbers using the newer (1.0mm) numbers.
Without knowing this you would assume the older cams had much more duration than newer cams.
Notice there is about a 46 degree difference between the two sets of numbers for opening and closing. 23 open and 23 close.
I'm convinced this has caused confusion for many people trying to decipher cam specs.
I hope this proves useful.
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Old 07-28-2004, 08:41 PM
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