'08 FLHX build

[Krennen]

Mike, I have been lurking here for a while and thought I would actually join in. I am planning a winter tear down of my glide this winter, the build I had originally compiled was this.
16952-06 SE Pro twin MCR heads
17997-99a adjustable push-rods
SE 255 cams
SERT
Thunderheader 2 into 1

I am aware of the intake port size difference on the heads, I have a machine shop that is going to open them up for me. I have been doing some research here and read that you do not suggest the 255 cams in a hi-comp engine. If I have done my numbers right, the heads should bump me up to about 10.3:1, which would not go well with the 255's.

I have a few questions that I hoped you could help with, what cams would you suggest for this set up,? I ride solo most of the time, but do ride two up with gear on occasion.

The second question is, the stock head gasket is .045 thick, I would really like to go with Cometic MLS head gaskets due to the increased compression, if I was to use a .040 gasket would have piston to valve clearance issues?

The last question is I am planning to have it dyno tuned, what kind of numbers could I expect with this build?


I sincerely thank you taking the time to read and reply to this post,
Krennen

[Mike]

Correct, the 255's would not like the 10.3 compression (detonation).

You did not indicate if your going to 103ci but would strongly recommend doing so for the amount of tq increase vs. additional cost.

In the SE cams the 251 or 257 would be good choices with the 257 being a better match for the thunder header. Still the T-header will fall off at higher rpms due to motor size (even at 96ci) while showing a substantial tq dip around 2700. Folding the baffle fins over helps this tq dip. There is another post from a viewer that did this and was very happy. A better choice would be the D&D Fatcat if 96ci, Boarzilla/quiet baffle or Bassanni Road Rage if 103.

With the bigger valves and decked surface you will have valve to piston clearance issues when using the Cometic .040 gaskets. Should be checked in any case. If you use the forged SE 103 pistons, clearencing will not be required.

As a 96, expect 100-105hp/tq. As a 103, 110-115hp/tq. Could go 120-125 with porting and the 257 cams and good tune (STD 5th gear).

[Krennen]

Mike,
Thanks you for your reply and information. I am leaning towards the Boarzilla pipe and the 251 cams. I can't seem to find a good 103 piston match for these heads, the SE catalog head/piston chart does not make sense. They have a cast piston listed with these heads showing 10.8:1 compression, I think that is a bit much for a cast piston. Which piston part number were you referring to? Can I run these heads with a bolt-on 103 kit, or do I really need to change the pistons due to the hi-comp?

My only question on the 251 cams are they are listed as .579 lift, the heads are listed to be good to .575, is this going to cause a problem?

I thank you again.

Krennen

[Mike]

Since the SE Performance heads are decked .060, you can run the kit 103 flat tops (pn 21966-07) for around 10.5 compression (adverstized 10.8 but typ slightly lower). Use the SE MLS head gasket (pn 16101-01, .045) with these. Unless you plan on running the motor above 6000 rpm routinely, the cast pistons are fine, will run quieter, less expensive and are coated for longevity. Problem is that the valve reliefs may require cutting for clearance. This is why the forged pistons show lower compression because the valve reliefs are larger (adding cc's). Many engine builders go with the forgings for this reason alone (cutting valve pockets not required). With the forgings, use the Cometic .040 head gasket.

The additional .005 lift of the 251's is not a problem. H-D typically allows up to .080 on spring clearances and .060 for valve to piston.

[Krennen]

Mike,
Thank you again, you have answered all my questions. I was not planning to go to a 103, but as you stated, the small price difference is worth it. I am going to run the 251 cams with the stock 103 piston set-up. I do not plan increasing my rev limiter past 6k rpm, so I should have no issues. I am going to clay check everything when I assemble it to check the clearances. I am shooting for the 100/100 hp/tq mark, looks like I will make it and then some :). I will post my dyno chart as soon as I get everything done.

Thanks again,
Krennen