Grinding Cam from T to E Profile

orange911 · 02-23-2007, 10:08 AM

Does anybody have the profile numbers required to walk into a cam shop and ask for an 'E' grind? I have a set of MFI T cams that I would like the E profile, but I would rather do it locally than sending them out. Also, what should these be hardened to?

WadeO · 02-23-2007, 08:07 PM

Send them to camgrinder, you can't go wrong with him.

Henry Schmidt · Henry Schmidt's Garage

When you grind a cam to a greater lift and duration without welding you reduce the base circle. Will it work ? sure
Bettter to just find a nice set of E cams.

Cams are cold cast and need no hardening after reginding.

PORSCHE "E"
DURATION .040” .050” VALVE LIFT CENTERLINE SETTING
I 238 230 .405” 102 3.0-3.3 mm
E 226 222 .393”

orange911 · 02-27-2007, 01:23 PM

Thanks for the feedback.

Henry, thanks for the specs.
What are the negative effects of a reduced base circle?

Does camgrinder build up his cams before grinding. Welding will definitely harden the cam, will this effect the rocker wear rate?

After posting the 1st request, I have been able to do more estimating for a complete rebuild and I am going to have to save up more than planned. It never ends.

304065 · 02-27-2007, 01:36 PM

The problem with reducing the base circle too much is it fouls up the valvetrain geometry. You want the elephant's-foot adjuster pointing at the head of the valve. If you grind down the base circle you can make up for it with the adjuster until you either run out of travel or there's too much of a side load on the screw.

John will probably chime in here but my understanding is that he grinds certain cams from new castings. These castings are made in a special mold that chills the wear surfaces of the cam lobes, so that once they are ground, re-hardening is not necessary. This obviates the need for environmentally dangerous processes like molten cyanide baths which are an element of re-hardening.

camgrinder · 02-27-2007, 03:53 PM

Orange911, you have a PM.

The 911 E profile on 911 T cams removes about .030" of material. (.060" across the base circle.) This puts the adjuster about .044" further out of the rocker arm.
Good used 911 E cores with an MFI drive are pricey, if you can find them. The new "chill cast" (47mm) billets I use do not have the mfi drive, it must be added at an additional cost.