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[Snakebyte]

There has been a lot of talk about cams and getting the perfect power range for cruising torque. I have looked at a lot of dyno sheets and I know a sheet is just a piece of paper, but let's face it everyone likes to brag just a little.
Ok so can we all agree that the only reason we full throttle is cause you want the power and or need it.
So what's the problem with running a big cam and 12:1 or higher on the street? Let's face it you could run 16:1 if you wanted on pump fuel in a air cooled engine on a 100 degree day and not have problems. As long as you end up with 190-200 CCP. All this hype about you can't run 11:1 or 12:1 on the street and be happy with how the bike runs. If your still at a decent CCP then there is no risk. The high compression motor has the same reliability as the 9:1 with small cams that's has the same CCP.
We are a obviously not looking at the lift here. We are simply looking at valve timing and compression.
Now with that said I have seen a lot of high duration cams make more down low, set up correctly, then the small cam builds that have a great low end grunt but end up plateauing early and then taking a slow dive. Having the rider wanting to turn the throttle more, but it's already at the throttle stop.

[HILLSIDECYCLE.COM]

Right on.
Scott

[05Train]

I'm running over 11:1 in my Night Train with a 625 cam.  The bike's stupid fun and I've never had it detonate.

It's all in the tune.

[HD Street Performance]

When the CR exceeds the Octane available all you get is a flatline for power due to having to pull timing and in extremes there is much added heat. The CCP is one data point and declaring victory based on that is not the whole picture. As soon as the late intake close (Atkinson-Cycle) is overcome and the benefits of added overlap are realized the dynamic cylinder pressure responds accordingly, assuming all the parts are working together the way they should. This is what enables and yields the higher horsepower. The success of these builds is on a case by case basis and takes planning. If it was as simple as targeting a CCP and ignoring the mechanical CR then there would be a lot more running that CR in these motors.
On a side note:
Remember the Crower Mileage Maker cams? They worked but by virtue of very wide LSA had nearly 0 overlap. Bad reversion though
A little more food for thought
http://www.mpgresearch.com/groups/engine-modifications/endyns-soft-head

[hrdtail78]

I have recently set up 2 engine at 11.5 for street use.  One is a 09 (touring) 120 w/ 662-2 and the other is a (99 dyna) 103 w/ DM598.  These cams are a lot a like.  CCP is over 200 on both.  Both are Delphi and both will be tuned TTS.  I have confidence my tuner can handle it.

A couple of things I take into consideration.  The 103 is a 5 speed and a much lighter bike.  It should be able to rev up quicker.  If I don't lug it, I shouldn't have detonation problems.  A higher gear, high map load, slow rev might induce detonation.  It's gear drive and I do have a 4 key.  This isn't for detonation but for battling the compression at higher rpm.  I will see how it goes.

The touring is a heavier six speed bike.  Even though these cams are close.  They will require different strategies for tuning.  I am willing to bet that the 103 will like the timing ramped up and the bagger will want a small gradual climb and wont climb as much.

I have been questioning CCP as of late.  It's the yard stick we use, but there is a lot of factors that play along that we cant tell from our test.  Does it show cylinder fill with overlap like would happen at 3500?  Does it show how a cam can bleed off compression?  Why isn't hot cranking compression ever talked about?  Things are different when things are expanded with heat.  Is ring seal as good when it's cold?  I was always taught to perform leak down hot and cranking compression on cold.  What is your guys take on it?

[HD Street Performance]

All good points Jason
Hot CCP yes that one, the real test because the forged pistons and associated parts are in operating condition. When a forged piston expands the ring lands change too
My own personal 07 runs a 662-2 and it is at 11:1. That is as far as I care to go. I don't care about what I leave on the table. I ride 2up mostly and just want it to be an enjoyable ride. I have plenty of power.

[HILLSIDECYCLE.COM]

We use about 200 ccp, as our theshold here, and trust me we like compression, as our AHDRA Mod bike ran 17.25 cr.
We just let the heads/cubes/cam/intake and exhaust do it anymore.

[Snakebyte]

Indeed a lot of factors can help with detouring detonation. I've been also messin around with the idea of a longer stroke makes the piston travel faster, this will also decrease detonation. The same thing goes with rod length. For a long time and still today people seem to think longer rods are better. I believe the shorter rods are better due to once again piston speed, but this time at TDC. Shorter rods mean the piston will dwell at TDC for shorter duration. Which helps with decreasing detonation as well. The shorter rod will also move the piston slower at BDC.
I really think the SE race crank in the 120r is a very nice piece. Longer stroke, shorter rods and forged, all they need to do is put races in the rods and weld it.
As a side note the longer stroke shorter rod will pull harder on the intake charge also.

[hrdtail78]

I have a long rod and a short rod engine.  You bring up some good points with them.  Does the shorter rod with it's harder pull on the intake charge counter act the leverage of the longer rod?  Still boils down to BMEP.

These are comparing a 4 5/8 stroke (short rod) to a 4 1/2 (long rod)  Apple to pineapples thing.  Faster dwell times vs a slow dwell time at BDC.  Bad things can happen at slow speeds.  Rings don't know how to react to it.  Exhaust timing isn't designed for it.  A purposely built engine will take all of it into consideration.

[Snakebyte]

I have a long rod and a short rod engine.  You bring up some good points with them.  Does the shorter rod with it's harder pull on the intake charge counter act the leverage of the longer rod?  Still boils down to BMEP.

These are comparing a 4 5/8 stroke (short rod) to a 4 1/2 (long rod)  Apple to pineapples thing.  Faster dwell times vs a slow dwell time at BDC.  Bad things can happen at slow speeds.  Rings don't know how to react to it.  Exhaust timing isn't designed for it.  A purposely built engine will take all of it into consideration.

I am ok with speeding things up to increase timing and compression at TDC. Defiantly has more benefits than slowing things down a tad on exhaust.
FYI having a shorter rod would would actually have the same effect as adding a little duration to the exhaust side of the cam. Wich accures at BDC. So it kind of a trade off.
Now if your running at really high rpm then I would consider longer rods. Like around 7000 rpm.
No dought a get topic the whole rod to stroke ratio many different angles to the equation, all of the opinions are correct and non wrong. Very fun indeed. 

[HD Street Performance]

"The same thing goes with rod length. For a long time and still today people seem to think longer rods are better. I believe the shorter rods are better due to once again piston speed, but this time at TDC. Shorter rods mean the piston will dwell at TDC for shorter duration. "

All true out of the context of a HD stock block street motor. The piston speed and side thrust on the already short skirt pistons become the hinge point not combustion theory. My point the motor won't last very long albeit may stay out of detonation that a shorter stroke longer rod motor may have experienced. Ring seal due to piston stability over BDC are a concern. Along with the ring seal cooling comes into play as the rings are the conduit to pull the heat out. A larger bore, >4.125", also helps preclude detonation. But that is not going to happen either for the same reliability reasons on a stock block.
The street is brutal as compared to the Engine Masters Challenge type motor as an analogy.

I am not sure what the point is of the discussion other than bench racing. Do you think this theory will push a 120r for example into the 160hp streetable neighborhood? It isn't that hard to get to a 150hp level and a reliable package but the aggregate torque suffers some normally aspired.

[hrdtail78]

I'm just bench racing.  Trying to bring up points to stir conversation.  I can quote you Denish but haven't found a lot of info on this with Harley style engines.

I didn't design my engines.  The short rod is a 120r and my 4 1/2 with 7.69's rods was put together with a lot of help from Randy T.  Used his already existing, proven combo.

[TorqueInc]

larger bore precludes detonation ?

[Snakebyte]

More squish area I suppose ?

[TorqueInc]

over a certain percentage of the bore diameter ,it becomes a problem.