Advancing and retarding cams
Thread Starter
|
Banned
Joined: Apr 2014
Posts: 678
Likes: 1
From: LA
Advancing and retarding cams
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
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
Last edited by Dun Roamin; Jun 3, 2014 at 10:01 AM.
Thread Starter
|
Banned
Joined: Apr 2014
Posts: 678
Likes: 1
From: LA
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.
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.
Tourer
Joined: Sep 2011
Posts: 252
Likes: 1
From: Kentucky
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.
Thread Starter
|
Banned
Joined: Apr 2014
Posts: 678
Likes: 1
From: LA
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.
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.
Trending Topics
Outstanding HDF Member
Joined: May 2008
Posts: 2,543
Likes: 19
From: Ashland Ohio
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.
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.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
The Best and Worst Harley-Davidson Moves of 2025
Verdad Gallardo
Sponsor
Joined: Dec 2007
Posts: 12,084
Likes: 829
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
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
Thread Starter
|
Banned
Joined: Apr 2014
Posts: 678
Likes: 1
From: LA
Some of us still live in the old days and in between areas. Now, "don't question just buy another" philosophy dominates.