We’re diving deep into the new 121 CVO VVT engine and we’ve found some interesting changes the factory has made compared to the previous Milwaukee Eight models!
This entire concept started with Jim Fueling … I have a 1990 fxrs 88” Evo with a completely redone and upgraded (springs, rocker arm adjusters, and valves which i machined) set of Jim fuelings 4 valve heads and this bike is extremely fast anywhere in the throttle range, I mean fast, the flow on these old Evo 4 valve heads are better than a M8 107” because of the polyquad port design and The spark plug is hemi type… the reason Harley don’t put a plug in center is time and labor with service tech… listen…take the M8 new head, where the compression release is and tap and relocate spark plug there, move compression release to where plug was…and these heads would be much more efficient and power effective. I have another set of the older Evo 4 valve heads going to modify even a little more for a Sputhe 104”… Frank Solenberg in Indiana was getting close to 120 HP from a 80” Evo Built properly (key word is properly) with them Heads years ago. There’s nothing new under the Sun! Just like HE says…
The solution is not another part, but rather following proper break in procedure so that the piston rings have the best opportunity to make a good seal against the cylinder walls. The Harley break in procedure is entirely wrong for these engines. They need a good ring seal because of the excess pressure this motor creates inside the crankcase. The break in procedure harley specifies in the manual does everything possible to NOT get a good seal. Ride it like you stole it and seal those rings up good and tight in the first 50 miles. Absolutely zero oil issues regardless of what venting system is on the bike.
Wow seems to me from the pictures,the valves seem much more shrouded due to the squish shelf. Plus gonna be more difficult to go to a larger valve. Be interesting to see what HD does with " stage IV" head design. Dig the new intake port but absolutely agree much more work needs to be done to exhaust port. Thanks for the peek inside.
This is some good stuff. Do you know If or When the heads can be bought over the counter? I am assuming you will be porting the head to see what you can get out of it. I have been wondering if Harley did a 121 CI to use in the King of the Baggers? The Indian is a 121 or 122 CI. Why is there a big gap between horsepower and torque? 27.18? Some sales people at Harley dealer are claiming all most the same horsepower as torque. I hope there is another video on this coming soon.
