Timing an E Cam
 

I am about to time the cams on my 911, I have E cams, a 70.4 crank, and S P/C's. I noticed that the E cams from 69-71 have a valve overlap of 3.15 and the 72-73 have an overlap of 2.9. Can anyone please explain why the difference, isn't an E cam an E cam regardless of year? What would you advise for my engine. Thanks for the help.

Only with the E cam do you need to specify which E cam. The 69-71 E cams were much "hotter" than the 72-73 E cam. Thus the need for 2 different timing specs.

You'd think so...
 

...but E cams are not all the same. The early E cam is in fact a bit hotter than the later ones.

I checked a couple books and came up SOL on part #s - they are all the same whether early or late E. Your only option is going to be to put a degree wheel on the motor and measure the lift of the cam.

Any idea where your cams came from?

I agree with l33t9eek, the are different cams. Early E-cams are the same as Solex cams, and later E-cams are what people ususually refer to as E-cams. I like the Early-E/Solex cams myself, and have a set in my 2.2. See BA's book page 108. I'll see if I can find the part numers.

Hope this helps,

JP

Thank you for the responses. Sounds like I have a little more homework to do. I believe these cams could be regrinds as there was a stamp on the back of one cam. Checking lift should give me the answer.

Please don't post duplicate questions otherwise I tend to give different answers in each one.:)

Thanks,
Sherwood