Cam timing question

[Classic 911]

Hello all

I am running this cam grind in my 3.2 short stroke and was wondering if it is beneficial to alter the timing, either retarding or advancing ?


WEBCAM Grind: 120/104

Valve Lash (Inch):
.004"
Valve Lash (mm):
0.1mm

Valve Lift (Inch):
Intake 0.476
Exhaust 0.449

Valve Lift (mm):
Intake 12.09
Exhaust 11.43

Advertised Duration:
Intake 284°
Exhaust 264°

Duration @ 0.050"
Intake 270°
Exhaust 248°

Lobe Center: 100°

SET @ 5.2 MM WITH .10 MM LASH


Cheers

[Zuffenwerker]

I think web pretty much hits the nail on the head

[stownsen914]

It's typical to time to cams according to the grinder's spec, unless you're trying to achieve a specific purpose like more top end, more mid-range, etc. This looks like a nice lumpy performance grind. Hopefully you're running carbs or ITBs.

[gled49]

I use specs as recommended unless I don’t like the valve to piston clearance, in that case I will adjust cam timing to suit.

[Jeff Higgins]

Boy, I would heartily second (or third or fourth) what these guys said. The folks grinding these cams know what they are doing. Unless you have specific, hard data from a dyno with these cams in your motor (not one "just like it") with both the altered and recommended timing, you're just flying blind anyway.

I think this notion had its genesis with the SC motor, where some guys started to tout altered timing to increase torque. Can't remember if it was advancing or retarding the timing. At any rate, I think on the dyno the "area under the curve" was largely unaltered, just moved around a bit. No real advantage, just a difference in "feel". I see these cam timing questions as kind of a lingering "hangover" from those days. Best to stick with the grinder's recommendation.

[Jeff Alton]

^^^^ Well said Jeff.

Cheers