Measuring my cam specs - did I do it right?
 

I measured the cams from my bench motor with a digital caliper this morning. Their part numbers match with Porsche's part number for Solex cams, but in addition to having "Solex" stamped on the end also have "Elgin" as well, which makes me assume a regrind in their past.

http://forums.pelicanparts.com/uploa...1145983255.jpg

To measure them, I took the maximum width from the lobe tips to the opposite end of the base circle and subtracted the diameter of the base circle from these numbers. This gave me lifts of .290 and .285. These numbers don't match anything on camgrinders tables.

This causes me to assume that the lift used to define cams is at the valve, including the ratio of the rocker, as opposed to the mechanical lift at the cam lobes. Is this correct? This seems odd to me as cast rockers are 1.4:1 and forged are 1.5:1, which would make cam specs listed in the tables as relative. Camgrinder, which ratio do your tables assume? If we have to calculate in the ratio rockers, do you also add in other components like the .004" of valve lash and does this 4 thou get multiplied by the ratio, as well? Anyhow, at 1.5:1 the cams come out at .435 and .428 and at 1.4:1 they are .406 and .399 respectively (sans lash).

Does anyone have a good guess as to which cams I have? They look somewhat like E cams from the table, assuming cast rockers. I obviously don't have a convenient way to measure the ramps or duration.

BTW, how do I tell if my rockers are cast or forged? (I'll go searching now) :D

One more detail. Look at the huge valve pockets on the pistons from the motor these cams came from:

http://forums.pelicanparts.com/uploa...1145984091.jpg

Doesn't this seem a litte extreme for 'E' cams? Not to mention that if they are 'E' cams, you can't grind Es from Solexes without weld up, which seems like a waste. I am totally confused.

You should be able to grind "E" profile on solex. They are almost the same with the Solex having slightly longer intake duration. I suspect that If you check the part numbers on the cams you'll find they were some kind of early cam and have been reground by Elgin to Solex specs. You need quite abit of clearance for these cams because the overlap is quite large.

-Andy

The Porsche part number on the cams are actually Porsche Solex. Camgrinders site also does not list E cams as an option for grinding only from Solex.

Send John (camgrinder) an email - he's extremely helpful and nice to deal with. Better yet - send him the cams and he'll tell you exactly what you have.

That's my next step if I can't figure this out on my own. The reason I am trying to discern what these are is to sell them and buy some DC40s or DC60s (assuming these aren't of this spec already). John has already been very helpful on other issues, too.

These are probably E cams ground to the Solex profile. The base circle is probably under 1.100".
The average 911 rocker ratio is 1.47-1. The factory 906 rockers are slightly higher. 1.49-1.

On cams with higher duration, the lobe is allready lifting the valve where you are measuring with your calipers. When you measure the
nose to heel (bottom to top of the lobe) vs. the base circle diameter, your lobe lift numbers come out slightly less.

Some of the early engines (non T's) had castings numbers similar to the solex cams with the E profile. (911-06?) The E profile has 102 lobe centers and the Solex has 97 degrees. Grinding these cams to Solex specs and moving the lobes to 97 isnt too good. I prefer to retain the E lobe centers and make what I call my Mod-Solex profile. This cam falls between the standard solex and the 911S profile.

Thanks John!