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[Dan_Lockwood]

With a chain drive cam, both cams rotate in the same direction.

With a gear drive cam setup, do they both rotate opposite chain drive cams? Or just one? Or neither?

If they do rotate opposite rotation, is there any evidence (testing) that lifters have a longer life with gear drive cams?

Also, with all the talk lately with the 117" etc upgrades and with cams etc, has anyone been measuring the crank runout on the pinion side?

Just wondering if they're better now than say back in the first 3 or 4 years of the 110".

[Dan_Lockwood]

I cannot believe that there are no comments or at least telling me I'm full of chit for even suggesting questions like this...

I guess it's how my little pea brain works.

[grc]

If you look at the cam chest from the right side of the bike, the crankshaft gear rotates clockwise.  That turns the rear cam gear counterclockwise, which in turn turns the front cam clockwise.  With the chain drive setup they all turn clockwise.  Thus the requirement for specially ground cams when switching to gear drive.

I can't imagine any scientific reason why the lifters would care which direction the cams turn.  They will care about the opening and closing rates of the lobes, which is part of the problem with 110 engine lifter roller failures.

All I can say about the pinion shaft runout is that in my reading I've gotten the impression that when new engines are checked for runout the average seems to be near .004".  There again, that's just the ones I've seen posted here and elsewhere, and is far from a scientific sampling.

Jerry

[Dan_Lockwood]

Jerry,

Thanks.

I just have a weird mind and it functions differently sometimes.

As long as the lifter is centered perpendicular to the center axis of the cam, rotation in either direction, as you say, should be the same force on the lifters.  I was just thing that with the Gear Drive Cam Noise thread going on right now, I'd ask the questions.

As far as crank pinion run out goes, I remember when HD raised their run out limits to .012" or .013" to avoid possibly some warranty work on the very early 110" motors.  I was just wondering if the later motors were coming in at a more normal run out.

Thanks for the reply.

[grc]

Hi Dan.  Gear drives would always be my first choice, but unfortunately the "new" normal at Harley isn't conducive to using gear drives unless you also true the flywheel assembly and provide a means to keep it from shifting.  The absolute maximum pinion shaft runout S&S allows is .003", and as I noted in that other thread it's best to be no more than .002" for best results. 

People might remember that not all that long ago Big Twins came stock with gear driven cams.  I find it enlightening that using older designs, older materials, older tooling, and older methods, Harley was able to make gear drives work.  Now with supposedly better design, materials,and tooling, they can't produce a crank that's precise enough to run gear drives.  But they can crank them out in higher volume with lower quality at lower cost, and that seems to be the strategy they've embraced.  With a rapidly changing market that includes a fading Boomer generation and increased competition, that strategy won't be sustainable IMHO.  Eventually people get pizzed off and refuse to pay more for less.

Jerry

[Dan_Lockwood]

My AMF Shovelhead has gear drive cam, but there's so much other noise, I can't tell if it's cam gear noise or just your typical Shovelhead...