Why a single cam?

[actonern]

When the twin cam was introduced, the explanation I recall for the change over the EVO was that the two separate cams allowed a more linear force vector between push rods and lifters, reducing side load on the lifter bores.

With the new single cams now pushing 2 valve springs per cam lobe instead of one, won't that bring back the same issues EVO had?

[glens]

Geometry may have reverted somewhat, but depending on the mass of the valves (do the two new intake valves weight more or less together than the single old one) it may not be as much of a backward step as it would seem.  And maybe it's more backwards...  There are likely other benefits with a single cam that are more important to this generation of engineers, who just may all have been in elementary school when the last decision was made.

[HV]

Honda has a small 4 Stroke with a single Cam...single Lobe !

[choseneasy]

I thought the 2 cam design with silent chains was used to remove noise from the motor. Less motor noise meant the exhaust note could be louder.....
 

[autoworker]

$$$$$$ (At least in part.)

[rbabos]

Look at the bright side. Valve timing will be better between the two cyls.
Ron

[Ohio HD]

Look at the bright side. Valve timing will be better between the two cyls.
Ron

       I would bet the real reason, and stay consistent over time.

[CowboyTutt]

They made a big deal about reducing the number of moving parts to reduce parasitic drag too.  With better modern metallurgy maybe the side loads on the lifter bores not such a big issue anymore???  -Tutt 

[BUBBIE]

Hardened-Replaceable Lifter Blocks would have been Nice addition... Think?

Some reason the lifter block looks different but Why? EWhat am I not seeing? 

signed....BUBBIE

[Lakerat]

They made a big deal about reducing the number of moving parts to reduce parasitic drag too.  With better modern metallurgy maybe the side loads on the lifter bores not such a big issue anymore???  -Tutt

I never knew the EVO's had an issue with side loads on the lifter bores.

[tankshift]

Hardened-Replaceable Lifter Blocks would have been Nice addition... Think?

Some reason the lifter block looks different but Why? EWhat am I not seeing? 

signed....BUBBIE

What blasphemy! You are questioning the ALMIGHTY WISDOM of the MOCO? You will burn in HD HELL.

[BUBBIE]

 



Take a Listen to the ORIGINAL.... Arthur Brown, FIRE 1968.... Fits this New 8 ball...

http://www.Bing.com/videos/search?q=God+of+Hellfire+Song&view=detail&mid=C996807F244696CEDD53C996807F244696CEDD53&FORM=VIRE

signed....BUBBIE

[ScottFree]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

[Ohio HD]

Is that the same reasoning they went back to a rear belt drive in the 80's?     For style and heritage....     


https://www.youtube.com/watch?v=3406C6HaXl4

[JamesButler]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

BINGO!  Winer Winner, chicken dinner!

"C'mon people.  This is Harley-Davidson we're talking about".   Truer words were never written...LOL...  Let's not overthink it.

Let's not also forget that the MoCo had a great run with the Evo motor.  However didn't the exclusive control of that technology lapse thereby letting in the aftermarket competition?  So, the MoCo scrambled and came up with the Twin-cam solution.  Along with that "new" technology came all the bullsh8t marketing terms which promote the latest as greatest. 

It's all about the bottom  $$$ line.  Most Harley owners know very little and care even less about technology, present company on this "Tech" forum excluded, of course.  Look into the eyes of the average Harley demographic and start spouting terms like "metallurgy", "side loads" and "linear force vector push" and you'll see them glaze over and begin to shut. 

Going back to the late 80's the MoCo marketing department learned quickly that if it dangles a nice shiny chrome part in front of those eyes and spouts terms like "nostalgia" and "independence" and "freedom", and then ties those terms in with the "new technology", it could sell a polished chromed turd to its demographics.

So when the MoCo bean counters discover a potentially catastrophic trending loss to the competition, it tells the engineering department to switch it up - not necessarily to "improve or innovate" - but simply change it up and let the marketing department control the herd...

[rbabos]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

BINGO!  Winer Winner, chicken dinner!

"C'mon people.  This is Harley-Davidson we're talking about".   Truer words were never written...LOL

Let's not also forget that the MoCo had a great thing going with he Evo motor.  However didn't the exclusive control of that technology lapse thereby letting in the aftermarket competition?  So, the MoCo scrambled and came up with the Twin-cam solution.  Along with that "new" technology came all the bullsh8t marketing terms which promote the latest as greatest. 

It's all about the bottom  $$$ line.  Most Harley owners know very little and care even less about technology, present company on this "Tech" forum excluded, of course.  Look into the eyes of the average Harley demographic and start spouting terms like "metallurgy", "side loads" and "linear force vector push" and you'll see them glaze over and begin to shut. 

Going back to the late 80's the MoCo marketing department learned quickly that if it dangles a nice shiny chrome part in front of those eyes and spouts terms like "nostalgia" and "independence" and "freedom", and then ties those terms in with the "new technology", it could sell a polished chromed turd to its demographics.

So when the MoCo bean counters discover a potentially catastrophic trending loss to the competition, it tells the engineering department to switch it up - not necessarily to "improve or innovate" - but simply change it up and let the marketing department control the herd...

Would these be the same people that dropped the ball on the v rod? Let's price it out of reach for most and offer next to no accessories. Sure, that will sell.
Ron

[JamesButler]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

BINGO!  Winer Winner, chicken dinner!

"C'mon people.  This is Harley-Davidson we're talking about".   Truer words were never written...LOL...  Let's not overthink it.

Let's not also forget that the MoCo had a great run with the Evo motor.  However didn't the exclusive control of that technology lapse thereby letting in the aftermarket competition?  So, the MoCo scrambled and came up with the Twin-cam solution.  Along with that "new" technology came all the bullsh8t marketing terms which promote the latest as greatest. 

It's all about the bottom  $$$ line.  Most Harley owners know very little and care even less about their engine's technology, present company on this "Tech" forum excluded, of course.  Look into the eyes of the average Harley demographic and start spouting terms like "metallurgy", "side loads" and "linear force vector push" and you'll see them glaze over and begin to shut. 

Going back to the late 80's the MoCo marketing department learned quickly that if it dangles a nice shiny chrome part in front of those eyes and spouts terms like "nostalgia" and "independence" and "freedom", and then ties those terms in with the "new technology", it could sell a polished chromed turd to its demographics.

So when the MoCo bean counters discover a potentially catastrophic trending loss to the competition, it tells the engineering department to switch it up - not necessarily to "improve or innovate" - but simply change it up and let the marketing department control the herd...

[Jaycee1964]

Just tossin it out there but with 2 valves for each action one would think less lift is necessary depending on valve size?  I have no idea the size of the intakes on the new motor but say they are 1.5" x2 would be basically a 3" valve area.  my 124" has a 2" valve.  Wouldn't they flow more air IMO at a lower valve lift?  With a lower lift less valve spring pressure would be necessary to close the valve?  A single cam opening 2 valves with decreased spring pressure at once would not have as much pressure on the lobes?  Wonder if they are running "c" lifters..   


Just tossin' it out there. 

[PoorUB]

At low lift the circumference of the valve means more than the diameter, (of course they they go hand in hand) two 1.5 inch valves equal 9.42" circumference, where a 2" valve equals a 6.28". So two slightly smaller valves will flow more air.

[Ohio HD]

I'm definitely not a cylinder head expert, but I think the biggest improvement when going to four valves is a higher velocity port(s), air speed is up, combustion should be better too over the twin valve style.

[CowboyTutt]

Valve lip circumference is the name of the game, just don't tell a HD consumer as there eyes will gloss over according to some reports!  LOL 

Why Yamaha invented the 5 valve head, until they needed more compression and the 5 valve head and cut-outs got in the way of that. 

So much for my 85 Yamaha 700 Maxim X with 5 valve heads.  It was a hoot for a while.  Came on like a 2 stroke on top from 7-10K rpm. 

Regards,

-Tutt

[Durwood]

Valve lip circumference is the name of the game, just don't tell a HD consumer as there eyes will gloss over according to some reports!  LOL 

Why Yamaha invented the 5 valve head, until they needed more compression and the 5 valve head and cut-outs got in the way of that. 

So much for my 85 Yamaha 700 Maxim X with 5 valve heads.  It was a hoot for a while.  Came on like a 2 stroke on top from 7-10K rpm. 

Regards,

-Tutt

Andy, that's cool. I bought a 1985 left over "Super Red" Maxim in 1987....That bike was fast!!! 10k, no problem.

Sorry for the thread drift, just took me a trip down memory lane..... Back to the regularly scheduled programming.

[mp]

To get back to the original question, yes, the pushrod angles on the Evolution engine were not perfect but it was no problem for about 99.9999999% of them.  And certainly the "solution" of the chain-driven  twin cams turned out to be a cure that was worse than the "disease", considering all the very well-known problems with them.  Can you say "needless complexity"?  Even today I can't understand keeping the chain drive on the M8, as the gear-driven cam in my Evo has never made a sound that I ever noticed.  I assume S&S is already "gearing" up to make millions on gear drives for Milwaukee 8's.

[Herko]

"...can't understand keeping the chain drive on the M8..."

Off the top, crank pinion run out requirements are widened with chain driven cams.
Chains work well, and looks like the MoCo upped their game a bit with tensioner design.

[PoorUB]

I can't understand keeping the chain drive on the M8,

Chains are cheep, leaves more room for manufacturing tolerances. Less money to stamp out a sprocket than machine gears, plus hole locations in the engine block don't need to be spot on.

[mp]

Sounds like all bad reasons to use a less efficient design on motorcycles that are well over $20,000 for non-CVO models.

[Matt C]

I'm gonna guess 'simplicity' and money. 4 valved heads are also superior (air flow wise) and take
allot less lift. Lower spring pressures/lighter valves overcomes some of the ails of the EVO v/t.

These things will have potential to take it to the next level, those heads are going to be kick-ass.

[Durwood]

I'm gonna guess 'simplicity' and money. 4 valved heads are also superior (air flow wise) and take
allot less lift. Lower spring pressures/lighter valves overcomes some of the ails of the EVO v/t.

These things will have potential to take it to the next level, those heads are going to be kick-ass.

I agree 100% Matt.

[glens]

They made a big deal about reducing the number of moving parts to reduce parasitic drag too.

Probably more like wanting to reduce the number of parts to decrease assembly time and increase assembly consistency.

I was curious about the term "parasitic drag" so looked it up.  Evidently it's an aeronautical term and pertains to air friction.  Not to be the terminology police or anything, but in this case it would be "parasitic friction" or generally "parasitic losses".  Have a look at page 3 of http://energy.gov/sites/prod/files/2014/03/f11/merit08_fenske.pdf for something very interesting.

[Don D]

I'm gonna guess 'simplicity' and money. 4 valved heads are also superior (air flow wise) and take
allot less lift. Lower spring pressures/lighter valves overcomes some of the ails of the EVO v/t.

These things will have potential to take it to the next level, those heads are going to be kick-ass.

Yep   
But MOCO is already playing a supply game on the heads.

[Ohio HD]

All you have to do to get heads is....  buy a bike,          or, get in business with another aftermarket that bought a bike for reasons other than the heads.

[Durwood]

All you have to do to get heads is....  buy a bike,          or, get in business with another aftermarket that bought a bike for reasons other than the heads.

[PoorUB]

Sounds like all bad reasons to use a less efficient design on motorcycles that are well over $20,000 for non-CVO models.

Who said it is less efficient? Looks like the push rods are straight on, better than the TC or Evo, less side loading of the rocker arms and lifters. Less moving parts, more valves, more flow at lower valve lift. In theory it should be a good deal. Now give the M-8 a couple years in the street to see how John Q-Public can find ways to destroy it to see if the theory holds up. It looks like a good engine, but time will tell.

[wfolarry]

The best thing they did was go to a single cam. The chain drive makes it easier to keep it quiet. There's a lot of improvements there that you're not seeing that will show up down the road as they start coming apart for upgrades.
If I was to improve on the 45* V Twin I would have done it the same way. There's a lot of potential in that motor with a lot less stress on it than those damn twinkies.

[FSG]

    there's lots of little things

the bevel/countersink on the inner cam bearing position

then clearing of the lifter bores for the cam lobes, easy when only a single cam

1st thing I'd be doing is measuring the bottom of lifter bores (current max cam lobe lift) to see what it is now and how much more could be taken off the bottom for bigger cams if needed

Go to a gear drive setup with an adjustable +/- 10 Deg Cam Gear, S&S, Andrews, other.   

[CVOThunder]

SO who's gonna be the first to make a set of 4 valve heads for the twin cam? Is it possible and wonder how it would look. Probably have to do the same to the covers but would they fit in the frame.

[JW113]

Four valve heads.
Push rods & rocker arms.

[attach=0]

Chain drive single cam.

[attach=1]

Gee, wonder where they got all that?

[attachimg=3]

History repeats itself.

-JW

[FSG]

History repeats itself.

   I had a CX Shadow 

[PoorUB]

SO who's gonna be the first to make a set of 4 valve heads for the twin cam? Is it possible and wonder how it would look. Probably have to do the same to the covers but would they fit in the frame.

Seems to me it was done already, about 15 years ago.

[mp]

Sounds like all bad reasons to use a less efficient design on motorcycles that are well over $20,000 for non-CVO models.

Who said it is less efficient? Looks like the push rods are straight on, better than the TC or Evo, less side loading of the rocker arms and lifters. Less moving parts, more valves, more flow at lower valve lift. In theory it should be a good deal.

I was referring only to the chain-driven cam being less efficient.  The new engine looks far better than the Twin Cam in most every way.  Of course, I recall a lot of people thinking the Twin Cam looked better than the Evolution and we all know how that worked out.

[CowboyTutt]

A 4 valve hemi conversion was available, but it never really delivered the performance advantage it promised at a practical price point.  http://thekneeslider.com/4-valve-hemi-heads-for-harley-big-twin-engines/ There just wasn't enough interest and development time for it.  Two valve technology meanwhile really took off afterwards and 4 valve head conversion development stalled out. 

Its why I keep suggesting just keep your TC a TC and use the technology out there for them.  It is currently in a high state of evolution and development, just use what is out there, and you will be much happier IMHO.

Regards,

-Tutt

[ocezam]

I thought the 2 cam design with silent chains was used to remove noise from the motor. Less motor noise meant the exhaust note could be louder.....

Single lobe?.  Doubt it. Unless it's from a lawn mower.

[les]

The best thing they did was go to a single cam. The chain drive makes it easier to keep it quiet. There's a lot of improvements there that you're not seeing that will show up down the road as they start coming apart for upgrades.
If I was to improve on the 45* V Twin I would have done it the same way. There's a lot of potential in that motor with a lot less stress on it than those damn twinkies.

I agree.


Sent from my iPhone using Tapatalk

[Templer]

A 4 valve hemi conversion was available, but it never really delivered the performance advantage it promised at a practical price point.  http://thekneeslider.com/4-valve-hemi-heads-for-harley-big-twin-engines/ There just wasn't enough interest and development time for it.  Two valve technology meanwhile really took off afterwards and 4 valve head conversion development stalled out. 

Its why I keep suggesting just keep your TC a TC and use the technology out there for them.  It is currently in a high state of evolution and development, just use what is out there, and you will be much happier IMHO.

Regards,

-Tutt

The site linked states for EVO and "early TC" motors?  Does it already exist M-8 conversion??

[mp]

The only reason to use a chain is ease and speed of assembly.  Evolution gear drive cams are dead silent.
As for hemi-heads, they do make power but they also make a lot of heat due to their inefficient combustion.

[moscooter]

 
I'm seeing chat about the chain drive, the single cam, the four valves per cylinder and (why) surrounding all of those things in the new motor.  What I'm not seeing much mention of is...................(2) spark plugs per cylinder.  Was and/or is that really necessary and I'm hearing that access to one set on each cylinder bank requiring the gas tank removal or some such.

[Jako1]

New case with balancer
The TC will be no more IMO once the MOCO redesigns the Dyna Chassis
The VRod is no  more after this year along with the FLD

[actonern]

The most recent American Iron magazine has a review of the new M8 bikes, and the author, Steve Lita, states...

"With the inception of the Twin Cam, the valvetrain required the use of two cams because of the necessary pushrod angle with the old two-valve heads.  But now, with the transition to 4 valves, the single cam comes back into play."

Does this sentence make any sense?

[PoorUB]

Yes.

[Piston Broke]

I'll bet on 'no'.

It's not the number of valves involved that matters, it's the relative position of the rocker arm shaft.

It's nonsensical on both counts, i.e. the why for the TC and the M8.

It's like saying, "The Sportster needs four cams because of the position of the pushrod tubes".

[rbabos]

The most recent American Iron magazine has a review of the new M8 bikes, and the author, Steve Lita, states...

"With the inception of the Twin Cam, the valvetrain required the use of two cams because of the necessary pushrod angle with the old two-valve heads.  But now, with the transition to 4 valves, the single cam comes back into play."

Does this sentence make any sense?

Only shows the twin cam wasn't needed in the first place or was it? Depends on how you twist words around on a new product when advertised.
Ron

[PoorUB]

The comment makes some sense, but it is kind of like the chicken or the egg delema. HD probably could have done something similar to the two valve heads, but with wider valve angles and more lift it would have been harder to do. Narrow valve angles and lower lift made it easier on the M8.

[Sunny Jim]

And the lifters? Are they the same old crappy lifters?

[FSG]

And the lifters? Are they the same old crappy lifters?

yes

[rbabos]

And the lifters? Are they the same old crappy lifters?

yes

Ah come on. They must have been tested for a million miles, right? Well, one good thing is they should have an easier life with reduced spring pressures.
Ron

[Ohio HD]

And the lifters? Are they the same old crappy lifters?

yes

Ah come on. They must have been tested for a million miles, right? Well, one good thing is they should have an easier life with reduced spring pressures.
Ron

Is pressure reduced in total? Smaller, but smaller x 2.   

[rbabos]

And the lifters? Are they the same old crappy lifters?

yes

Ah come on. They must have been tested for a million miles, right? Well, one good thing is they should have an easier life with reduced spring pressures.
Ron

Is pressure reduced in total? Smaller, but smaller x 2.   

I'm guessing of course at x2 per lobe would still be less. In time we should have some real figures to compare with. If more, well that just adds fuel to the lifter fire, right?
Ron

[Ohio HD]

And the lifters? Are they the same old crappy lifters?

yes

Ah come on. They must have been tested for a million miles, right? Well, one good thing is they should have an easier life with reduced spring pressures.
Ron

Is pressure reduced in total? Smaller, but smaller x 2.   

I'm guessing of course at x2 per lobe would still be less. In time we should have some real figures to compare with. If more, well that just adds fuel to the lifter fire, right?
Ron

Yes    

And I wasn't poking at you, just wondering if they will be less.   

[gregm]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

[gregm]

ScottFree, my 2005 TC has four chromed pushrod tubes converging on the "timer" cover. Am I missing something?

[Piston Broke]

Perhaps it's in the look and the 'back to roots' concept?

The TC cost them a bit in bad PR and warranty ... and consumers double in replacement.