Hello,I have a Screamin' Eagle Twin Cam Conversion Kit - 103CI to 110CI
Part Number 92500033
1st. my bike is in storage and will not be installing this kit until the spring. I am looking to upgrade the 9.3:1 pistons to a higher compression.Then cams to match.I like the power but more of a low rpm torque guy , Does anyone know the specs on the heads? ( cc,s, intake, exhaust, valve lift). The pistons, Do they raise flush, below or above with the cylinder? I,m not a tec but know how to turn a wrench.
Any help on upgrades would be appreciated.
Thanks!

 

It would help to know the make/model of the bike.

If you like torque off idle and strong into the mid range, install the kit as it comes but replace the .045" OEM head gasket with a .030" Cometic MLS gasket. IIRC, the 110 heads have a 95cc combustion chamber, intake valve is 2.120" and will accommodate cams with up to .660" lift. The pistons are flat top and if they follow the pattern of most 110" top ends, the pistons will TDC about .005"-.007" below the deck.

You will need a fuel management system and a dyno tune with that kit.

 

Thank for the info djl. My bike is 2011 heritage softail. Cobra AC, andrews 37H cams, andrews adj. rods, ss lifters, cam plate and oil pump. Freedom Performance tru duels, Power Vision with Target Tunes. I was thinking going with 10.25.1 pistons, 0.045 gasket. According to Big Boyz calculator that should bring up my Static Compression 10.66:1. Then looking at Red Shift 576 cams.
I like to bring the Static compression up just to have later if I ever want to go with a mid range - higher torque cam I can just change the cams. I do like your set up. Just changing the oem .045 gasket to a .030" Cometic MLS gasket would save me $$$. What's your opinion ?
P.S. Also I have a 50mm Throttle body with 4.9 injectors to install.

 

I assume you are going to install the kit referenced in your OP? I won't go into the weeds and the following is JMHO.

The MoCo says that kit, installed as it comes, will set static CP at 9.3:1. So use the BB calculator, insert the known data points like bore, stroke, chamber volume and head gasket thickness and SE255 cams. Insert "assumed" values for deck height and piston dome volume. 110 pistons are typically below deck .005"-.010" and the pistons are flat top but with larger valves the dome volume value will be greater than the default -1.5cc value; I used three in the attached example; that's your baseline. Now all you need do is change the head gasket thickness to .030" and you will see the corrected CR and CCP increase to values that are higher and very manageable; compression releases not required at this compression level but would be nice to have and I would install them; not sure if '11 models come with ACRs but suspect the harness is there, the heads are probably drilled for them all you need do is install the ACRs and activate.

You have the Powervision and the bike should run well with a proper dyno tune. The 255 cams make plenty of TQ but HP, not so much. The 50mm T/B will help the HP side but don't expect big HP numbers.

One way to skin the cat and, as always, JMHO.

 

Thanks brother, something to work with. But you would keep the head gasket bore at 3.910 and not go 4.0? The static CP keeping under 10? Changing the head gasket to 0.030 with your BB the SCP goes to 9.55:1, CCP is 9.26:1. The heads came with the kit and have ACRs. I like the low torque but also like a little more HP over 10.0 CP.

 

Increasing head gasket bore from 3.910 to 4.0 at .045" head gasket decreases corrected CR from 9.04-9.01; the difference is lost in the overall calcs.

This is why I hesitated getting into the weeds. Like I said in my previous; forget about static CR, it is just a number and the motor never sees it. Most builders will target 9.3-9.6 corrected CR keeping CCP in the 190-195 psi range which is what you should be looking for. Pushing CCP up close to 10 and CCP 200+ could present a tuning challenge with the 255 cams. I run a stout 98" motor at 10:1 corrected CR and CCP at 212psi but I have one of the best tuners in the country nearby and the bike runs cool and strong with no issues. OK for me but I would not recommend that for others; OK for others but they need to go there on their own and not at a suggestion from me.

Most builder also target .030" for the squish band, i.e. the distance between the cylinder deck and the head surface. With the .030" head gasket and say .007" piston below deck, your squish band will be .037" which is OK but could be better. If you want to do this right and know exactly what you will end up with, do what most builders do and measure everything. Mock up the motor and measure the deck height then have the cylinders trimmed to set deck at 0.00". Have the combustion chamber CCd so you know the actual and if they are different, machine the head surface to equalize. I did some looking and the OEM CVO piston dome volume is -2.8cc so my -3cc guess wasn't far off. I know it's a bit of work but what I do with every motor I have built.

So, to summarize, measure for accurate data, or not and go with assumptions and target CCP at about 195psi and corrected CR in the 9.3-9.6 range and call it good; I think you will find the bike a lot of fun. Get it dyno tuned and ride it. If you want more HP, you are going to have to change cams and those cams will come the a later intake close which will mean heads will have to be decked to keep CCP and corrected CR in a "happy" place. Good luck with the project.

 

Thanks djl for taking your time to explain , great advice!

 

A strong 110" can produce 130/130 without breaking a sweat.
Scott

 

Scott at Hillsidecycle tell me more please.