Having clicked through about 20 pages of search results, I cannot find any topics specifically about "advancing and retarding cams".

I wondered if folks would care to share their practical experiences with various cams?

In the most simplest of terms, advancing a cam tends to move the power down in rpm, and retarding it/them tends to move it up the rpm ... but, remember folks, life is never just that simple.

I guess I'm a cheap skate who'd rather spend their timing fiddling with their engine - and learning at the same time - rather than just throwing money at a problem, and so I'm thinking of playing with mine.

I have an EV23 and more than enough torque (21T compensator) - I'm wondering if anyone has retarded one of them to move the power up a bit?

Advance ----------------------------------------------- Retard

begins intake event sooner -------------------------- delays intake event
opens intake valve sooner --------------------------- opens intake valve later
builds more low-end torque -------------------------- builds more high-end power
decreases piston-to-intake-valve clearance -------- increases piston-to-intake-valve clearance
increases piston-to-exhaust-valve clearance -------- decreases piston-to-exhaust-valve clearance

It strikes me, if you've got enough torque to spin the rear wheel low down, you may as well sacrifice a little of that to make more HP higher up.

But what I read is that 2 degrees equates to about 240 rpm of a difference and 4 degrees ... 480 rpm.

I see quite a few dyno charts for automobiles were people are playing around with degreeing. Not a lot for H-Ds.

Thanks

 

advancing will move the power to the left,retarding will put the power higher in the RPM band

 

Yes, that's the simple theory but by how much etc.

Specifics please ... dyno charts especially welcome.

Interestingly enough, I have heard of some heads, depending on the intake port benefitting all round (torque and HP) by retarding the cams.

 

Buy a cam to fit the build.

 

Do the heads play a role? I have hemi-performance heads on my 113 and their site instructs to retard timing 3-5 degrees due to their head design. I pulled mine down 3 deg and it's running very well, with much less detonation on the top end.

 

Your looking for cheap upper end power by doing this. Better to bark up a diff tree.

 

Yup, controlling detonation something else that this is used for.

Nope, there is life beyond searching for upper end power (personally, I'm not in the "power" league at all).

I've rarely read about folks recommending H-D cams to be pushed 5 degrees.

 

You really don't see much retarding going on, any more, and very little advancing. Crap, I missed this was an EVO. 4* you would notice, but I don't think I would really wish to move those 27s that far. You may lose way more than you really want off of the bottom.

That being said, why not simply try the 2* wheel. I had a twinkie that the crank builder screwed up the very end of the shaft, and the bike could move timing back and forth. I could tell when it advanced itself. Had to fix with a piece of feeler gauge wedged in the flat of the crank. But, it would move almost 4* when I put a degree wheel on it before hand.

I realize you have minimal choices as compared to a TC.

You could try it, but don't really think it will gain what you are thinking. But, I'm not well versed in EVOs, like say... Kirby is.

 

Age-old automotive info was if you had to move it more than 6* either way you have the wrong cam.
We used to degree Shovel and Evo cams all the time years ago,(some of these johnny-come-lately shops wouldn't have a clue as to how that's done.......hahaha) as those drive gears could be moved as needed to correct, and juggle.
How much it can change things depends on several factors.
Can't really do too much about it in T/C land.
Scott

 

Thanks. I think you highlight another factor in all this ... in the old days, the choices in cams were far less, hence there were in between areas worth exploring.

Some of us still live in the old days and in between areas. Now, "don't question just buy another" philosophy dominates.