Discussion and questions related to the course How to Degree a Cam
i’ve attempted to dial in my cams after setting valve lash at base circle of cam and rocker arm on Honda B16 vtec head. (The way factory specifies to .007” intake and .008” exhaust.) Cam card says to check lash at valve tip (with same specs) which seems to be quite an impractical way to do it. Would you get totally different readings checking lash at valve tip instead of cam base circle?
With the intake opening event set as per the cam card, closing event is out by 2.5 crankshaft degrees.
Exhaust opening event is set as per cam card, closing event is out by 9 crankshaft degrees.
How often is the cam grind wrong?
Surely I must have set lash incorrectly but seems like it’s out by such a long way.
attached is the cam documentation
As an update, I have purchased a new set of angled feeler blades to get me under the valve tip and have set the lash at that point as per the spec sheet. The duration on the cams is still out by several crankshaft degrees.
If you have doubts about camshafts being grind according to the spec sheet you can send them to a shop and see if the camshafts are in compliance with the spec sheet.That is what I would do if I were in your place.
I haven't dealt with the Skunk 2 brand of cams however I'm wondering if they have specified their timing events with the valve lash set to zero. I note on the cam information the duration is specced at zero lash so it's possible this could transfer across to the timing events too. Specifying valve lash at the valve tip is a pain but not uncommon. Due to the rocker ratio, setting the lash at the cam lobe/roller will give you inaccurate lash compared to the recommendations.
So I've set the vash lash (measured at the valve tip) to zero.
Spec's I got now with intake opening event set to spec, closing event is 4 crank degrees out
Exhaust opening event set to spec, closing event is 2 crank degrees out.
I'd like to see it spot on but at what point to you call it close enough?
Also why would Skunk2 provide you with two different lash settings? At what point do you set the "tappet clearance" to 0.007" and 0.008" if all the timing events are measured from a zero lash condition?
It would be a little unusual for the cam manufacturer to call for a specific lash but then require zero lash for the degreeing process but also not unheard of. You're getting to the point that i'd split the difference. Particularly if you're going to also test the cam timing on a dyno then you're close enough that it doesn't matter.
When I had a mystery set of cams Skunk2 sent me a detailed spec sheet for their pro 1 cams that I have attached.
It calls out all measurements taken with 0.000 tappet clearance.
My assumption is you degree them, then set the lash.
I'm assuming you already have your cams buttoned, but maybe this info will help someone else down the line.
*Edit* it is interesting to note on this sheet they show the tappet clearance measured at the cam, with no mention of the clearance at the tip of the valve.