M8 power output

[BigT]

I'm seeing some of these dyno runs from the 117" M8 making a little under 125 hp/tq with 11:1 compression. I'm making pretty the same power with my Twin Cam with the bolt on 110 cylinders and basic head work, Tman 577 cams and less compression. I doubt my heads flow as well as the 4 valve head. Kind of wonder why we're not seeing the M8 making more power.

[hd06]

 This is the first year for M8 things will get better.

[trex]

With the 4 valve heads I wonder what an over square M8 would run like. 117 size bore with early 88in. TwinCam stroke of 4in. Appropriate cam and 11-1m comp. Seems like it would be a screamer

[SoZo]

Star Power 117 build...

[SoZo]

Fuel Moto 117

[Don D]

 I doubt my heads flow as well as the 4 valve head
But they probably have better velocity and have enough flow to feed the motor and not choke it in the RPM range it runs

[Matt C]

A big advantage is mixture motion (tumble vs. swirl).
That, and the valve train is lighter, favoring higher RPMs.
A 2V head will still move enough air. 

[Don D]

Swirl, 2 valve, better for lower rpm motor, 4 valve tumble, great for higher rpms and over camping will send low end torque in the dumpster in a hurry

[harleytuner]

Here's a 114 I did.  This was before he took it in for a new oil pump.  It was sumping pretty bad.  I could drain the sump, make 4 pulls on the dyno and get 18oz back out of the sump.  Woods cams. Head Hoggers heads[attachimg=1]

[BigT]

Which Woods cam?

[harleytuner]

Which Woods cam?

M8777's

[Matt C]

You don't need allot of cam, b/c the valve curtain area(s) (added together) are plenty big.
So now, will we be able to use these heads? Will the bottom end take 7,8 or 9000 rpm? I doubt it.

[1FSTRK]

I'm seeing some of these dyno runs from the 117" M8 making a little under 125 hp/tq with 11:1 compression. I'm making pretty the same power with my Twin Cam with the bolt on 110 cylinders and basic head work, Tman 577 cams and less compression. I doubt my heads flow as well as the 4 valve head. Kind of wonder why we're not seeing the M8 making more power.

No one is making large improvements with the M-8 over the Twin cam when it comes to HP/CI or HP/CFM. The the over all intake design as delivered from HD just is not that great. Many mistakenly believe that 50 percent more air flow was all that was needed. I also do not think two valves, two springs sets, and a bigger rockers weight less than the single valve twin cam setup. All that load is now on the same old C lifter that was no good in the twin cam.

[SoZo]

I'm seeing some of these dyno runs from the 117" M8 making a little under 125 hp/tq with 11:1 compression. I'm making pretty the same power with my Twin Cam with the bolt on 110 cylinders and basic head work, Tman 577 cams and less compression. I doubt my heads flow as well as the 4 valve head. Kind of wonder why we're not seeing the M8 making more power.

No one is making large improvements with the M-8 over the Twin cam when it comes to HP/CI or HP/CFM. The the over all intake design as delivered from HD just is not that great. Many mistakenly believe that 50 percent more air flow was all that was needed. I also do not think two valves, two springs sets, and a bigger rockers weight less than the single valve twin cam setup. All that load is now on the same old C lifter that was no good in the twin cam.

The potential is there... The current intake and exhaust offerings are not capable of flowing what the heads can flow. The heads with professional expert porting (CNC Heads flow almost NO better then stock)  with stock valve sizes can make big improvements in the exhaust port and good gains in the intake. Larger valves make big strides... Cam profile is totally different, overlap needs to start at 100mm lift to get things flowing. There is no Borizilla size exhaust yet.. Fuel Moto is working on large stepped 2 into 1 which will greatly enhance exhaust savaging and HP capability.  The screeming Eagle Throttle Body and intake have a bad design where one cylinder flows 55cfm less the the other(I forget front or rear){the SE intake can be worked by porting to flow more} HP INC has a better 62mm setup which flows substantially more. ALSO there are not many high compression pistons out yet... most are flat top @10.5:1. 

[1FSTRK]

I'm seeing some of these dyno runs from the 117" M8 making a little under 125 hp/tq with 11:1 compression. I'm making pretty the same power with my Twin Cam with the bolt on 110 cylinders and basic head work, Tman 577 cams and less compression. I doubt my heads flow as well as the 4 valve head. Kind of wonder why we're not seeing the M8 making more power.

No one is making large improvements with the M-8 over the Twin cam when it comes to HP/CI or HP/CFM. The the over all intake design as delivered from HD just is not that great. Many mistakenly believe that 50 percent more air flow was all that was needed. I also do not think two valves, two springs sets, and a bigger rockers weight less than the single valve twin cam setup. All that load is now on the same old C lifter that was no good in the twin cam.

The potential is there... The current intake and exhaust offerings are not capable of flowing what the heads can flow. The heads with professional expert porting (CNC Heads flow almost NO better then stock)  with stock valve sizes can make big improvements in the exhaust port and good gains in the intake. Larger valves make big strides... Cam profile is totally different, overlap needs to start at 100mm lift to get things flowing. There is no Borizilla size exhaust yet.. Fuel Moto is working on large stepped 2 into 1 which will greatly enhance exhaust savaging and HP capability.  The screeming Eagle Throttle Body and intake have a bad design where one cylinder flows 55cfm less the the other(I forget front or rear){the SE intake can be worked by porting to flow more} HP INC has a better 62mm setup which flows substantially more. ALSO there are not many high compression pistons out yet... most are flat top @10.5:1.

Well the heads already flow 50% more than the Twincam heads and make the same HP/CI so I do not think bigger valves and even more flow is a cure. The rest of the parts do play in but just go to show that slapping four valves on something is not the game changer.  Yes they will with time catch up but it will in the end not be about CFM numbers from the heads.

[hd06]

 M8 is only little over a year old look how far T.C. have come in 18 years and they started with 88 C.I. M8 will only better.

[1FSTRK]

I may not even be riding in 18 more years 

[SoZo]

I may not even be riding in 18 more years 

Tri Glide.... with a 124M8... woot

[1FSTRK]

I may not even be riding in 18 more years 

Tri Glide.... with a 124M8... woot

If we take the emotion out and disregard the "newer is always better" philosophy we are left with the numbers. For my money, if you want great reliable power in the couple years take the amount of the sales tax on a new bike, add the amount of money you lose on any new vehicle when you drive it off the lot and put that into any Twin cam and you will have a great reliable motorcycle that that you can ride today.  I have a 4" stroke 5speed Road king and a 43/8" stroke 6speed Softail and both have been delivering trouble free miles at over 1.2 HP/CI for ten years. 

Want a new bike, fine buy one they are pretty. Want a new bike because the new motor is a more advanced, better performance platform, don't kid yourself there is different, and there is better, the two words do not mean the same thing. We had this same discussion when I posted here that the 120R would give average street HP with all the PMS and maintenance of a race engine and that made 120R fans all upset but was true.

As stated someone will figure out what needs to be changed in a M-8 to make it what it should have been from the beginning but it has not happened yet and may be a while with the learning curve that comes with a low rpm, long stroke, 4 valve head design but until then for the sake of the "Tech" in Harley Tech Talk let us be honest about what M-8 is and is not in its present state.

[BigT]

  I think the M8 is a better performance platform than earlier motors. The stock heads flow in the 300+ range, wider cylinder/ head bolt spacing allowing for future bigger bores. I've talked to a few head porters and hear the same thing that it's just going to take some time for the after-market to develop cams and exhaust systems. My M8 is is the the smoothest running motor vibration wise that I ever owned in 40 years of riding just a slug over 3000 rpm at this point.

[Larry757]

What no one understands when it comes too the M8 power is when and how it makes it. M8 Makes it now doesn't have to "come on" it's instant. Less power quicker will accelerate quicker than more power later. Passing after the finish line doesn't matter!!

[BigT]

I'm hoping S&S comes out with M8 "bolt-on" cylinders with steel liners this winter! It looks like the cases will take a 4.250 bore using resleeved cylinders (Hot Shot Motorworks) Not sure how big you could go with the much thinner steel liners.  131" would be nice!

[HD/Wrench]

http://www.harleytechtalk.com/htt/index.php?topic=101154.0

[irishrover]

Limiting factor on big power on any Harley motor is the 45 degree cylinder angle. You just can't turn the RPM's needed to make HP. YOU can make a lot of Torque, now before you all tell me to F-off look at what you have. 131inch motor with 135-150 hp with 130-140 ft lbs, now that's a motor that is definitely not what I would call a daily driver, it won't be smooth and I don't think you would want to ride it two up to California from the east coast, But that's not my point Now look at a Ducati V twin 90 degree cylinder angle 1200 cc or basically 75 cubic inches and there making in the case of my multistrada 160 hp with around 110 torque and and it runs as smooth as a babies axx . All im saying is they are what they are, so injoy it I wasted so much money on my roadking and its still a rough riding slow pig compared to my Ducati. but its your dough 

[Hossamania]

You forgot to mention that the RoadKing weighs about 200 pounds more than the Multi, but looks much better doing it.....