What is Twin Cam?

[Trainguy]

The top ends are very similar with one another and do use the same breather setup. But, they have different heads and rocker arms. The geometry of the pushrods with the Twin Cam vs. the Evo are not the same. The Twin Cam has 2 cams. Each cam has 2 lobes ( one exh. and one Int. ) The single cam Evo motor has just one cam with 4 lobes ( 2 Int. and 2 exh. )
The single Cam Evo is also centered in the motor, gear driven by the Pinion shaft.
The Twin Cam motor has 2 cams that are offset to the Pinion shaft but are still driven off the shaft via chain ( H-D ) or gear ( S&S )
Because of the difference in the location of the cams, you end up with longer pushrods with the Evo and a different geometrical angle into the heads.
As far as the oiling goes, the Twin Cam motor uses an internal Gerotor oil pump driven off the Pinion shaft and sends the oil up threw the pushrods to the top end. The Evo style motor uses and external style pump that is also driven off the Pinion shaft via gears and also sends oil threw the pushrods to the top end.

Kathy, Will You Marry Me?

 

[Nukeranger]

You just have to admire a girl who sells Stripper Juice and shows her intelligence by talking technical:2thumbs::2thumbs:

 

[BadBrad]

Thanks Biker Babe. You're my ace in the hole! You gave some very specific differences between twin cam and evo, so how is it that the 117ci is both? Is it just the heads and rocker arms? Obviously, the single cam is evo style. But how is our top end considered twin cam when it functions off a single cam? When we purchase parts for the top end, it's always noted as twin cam. The geometry of the pushrods can't be any different since they come from a single cam. I think V said that it's because of an improved breather/air flow. I thought it might have something to do with the way oil flowed from the heads back down to the reservior. It's all a little confusing to me. It's easy for me to sound like I don't know what the hell I'm talking about. This sure doesn't help.

 

[Tom Chop]

BB Came Up With The Proper Answer

Biker Babe; your explanation of the rocker arm geometry is right-on. The

twin-cam motor tries to address the mis-alignment of the rocker to lifter

mis-alignment. Just take a look at a Sportsters arrangment; four cams to

keep the alignnment as even as is feasable. Our Evo motors push the lifters

pretty hard against the lifter blocks wearing them and other valve train

parts rather quickly.

One more thing before I stop my dissertation. I wish that I, for one could

use the Gerotor oil pump on our Evo`s. The pressure and sumping are

vastly superior to any available to our oil pump type and they are

adjustable to boot. Wouldn`t that be nice? Just MHO. :zz2cents:


Tom Chop :choppersmiley:

 

[BBChopper]

Hybrid???

Biker Babe; your explanation of the rocker arm geometry is right-on. The

twin-cam motor tries to address the mis-alignment of the rocker to lifter

mis-alignment. Just take a look at a Sportsters arrangment; four cams to

keep the alignnment as even as is feasable. Our Evo motors push the lifters

pretty hard against the lifter blocks wearing them and other valve train

parts rather quickly.

One more thing before I stop my dissertation. I wish that I, for one could

use the Gerotor oil pump on our Evo`s. The pressure and sumping are

vastly superior to any available to our oil pump type and they are

adjustable to boot. Wouldn`t that be nice? Just MHO. :zz2cents:


Tom Chop :choppersmiley: