I was thinking about doing a 107 kit on my 2011 FXDC since Im already doing a 117 on the Streetglide but decided against it. I will keep it at 103 (when I bought the bike Bellmore Harley installed the 103 cylinders for free as part of a buying the bike). I sent out the heads to be CNC polished and ported. I orders a Bassani Road Rage 2 into 1 exhaust, got woods cams and will be using the TTS tuner. Now my question is what about the pistons. Should I leave the Harley cast iron flat tops that came with the 103 kit or can someone recommend another piston and what compression would they recommend.

 

They're cast aluminum not iron. Which wood cams? What size valves?

 

Youre right they are aluminum. I was typing and thing about cylinders and other things. I will be running Woods 888 cams. Im pulling them out of my 103 Streetglide since Im building it up to a 117. They ran amazing by the way. The SG is running 109 horse and 118 tourque with head work, 58mm tb, 103, and D&D Fatcat.

Regarding valve size on the heads. They will be 1.900 intake and 1.615 exhaust. I asked them put automatic compression releases on the heads as well since I have those on my SG as well. And also in case I decide to bump up to a 107 in the future.

 

I would recommend Wiesco or Je pistons.

 

Depends on what your goals are. If you're just looking for a little more compression, you can switch to .030 head gaskets, which is what I'm doing. I'm certainly not an expert, but I've been given the impression on the research I've done that the cast pistons are fine as long as you're not spending much time above 6,000 rpm.

 

You could achieve the compression you need for that cam with the stock pistons by decking the heads but you could run into clearance issues with the stock size valve reliefs and oversize valves. Wiseco makes a forged flat top with bigger valve reliefs but you'll still have to deck the heads quite a bit. I'd just run the se forged high comp pistons like you had in your stage 4. Are the pistons out of the sg still in good shape? The pistons will probably end up .005"-.008" below deck so I'd run a .030" head gasket. Shoot for 10.5-10.6:1.

 

I would use forged piston and spend the extra money. Because the metal gets heat treated it goes through the annealing process that a cast piston does not. Since the pistons get super hot and then cool, the metal characteristics in the cast piston will change because it's porous and cause them to break down faster. I would also run 10.5 to 1 compression ratio. The first thing to consider when determining the mechanical compression ratio is, whether the engine will use 93-octane pump gas. What cams you are going to use. I have not had any problem using 10.5 to 1. Just my two cent.

 

Assuming pump gas, cam is definitely the deciding factor of compression. You could have one bike at 9.5:1 and one at 12.5:1 with the same safe, streetable corrected compression ratio depending on what cam you're using.

 

I didn't even think about using the SE pistons you mentioned that are in my SG. Thanks. good call. I will see how they are on Monday. I don't think they are in bad condition. I mean I hardly ran her above 5000 rpm and if I did it was for a few seconds. The stage 4 build has 9000 miles on it. Let me ask you this. If I keep the FXDC at the 103 build should I still install automatic compression releases or should that just be done if I had a 107 because the work says to drill the heads so I can install the automatic compression releases. it can always be stopped since they only just got the heads. The 117 build is starting on Monday so I will know by then.

This is my FXDC. I just installed floorboard and used the old ones of off my Streetglide to see how they feel. I also ordered the Bassani road rage 2 into 1 exhaust.

 

I would definitely run compression releases, whether manuals or the autos you planned on, it would be a good idea with the 103 at 10.5:1. Interested to see how this does and how the bassani works, keep us posted on both builds.