I am relatively new here and there are a ton of forums and lots of great info. I have a 06 street bob with the 88. I have a SE intake, a V&H propipe, and a SE 203 cam. I know that today is the day of big bores but I have a different question. I want to try and find out if I put a set of SE kompressor heads on my bike what kind of gains I can expect if any. I know that they are basically the same heads as my stock heads that have been decked to rains comp. Will this raise in comp have any benefit? Would like to see what I can milk out of the 88 before I go bigger. Would having the SE heads cleaned up and worked a little help any? Thanks in advance

 

It would pick up a little torque by raising the compression and probably help a little more having them cleaned up but definitely not worth the time and money imo. Spend the money it would cost to buy the heads on a big bore and have your stock heads cleaned up. Just tell everyone it's still an 88", that would be more fun. I'd swap cams at the same time. Your stock 06 heads can handle close to .600 lift. There's a bunch of much better cam options. If you want to stay se, I've had much better results with the 204 than the 203. You must have got an early set when they still made them for 06-up. Where do you want the power?

 

I would like most the power on the bottom end. I do not scream around over 4000 very often.

 

Ok, so I may need some education and clarification here. I understand that there is nothing better than displacement. I do not see how you get so much more out of going 7-10 cubic inches (100 cc's) bigger on your bore.
This is the reason why I would like to do the head swap, maybe work them a little and see what I get. It looks like to me that everyone says BB kit, but at the same time they are doing a cam swap, and heads.

I know that a bb kit can get you up to 10% gains, if I remember reading correctly. But to get the numbers people are getting when they do their builds I know it is a combination of many things. I have seen data on websites that 88 can get 100/100 or close to that. So I would expect that if I do the heads and on what I already have would I not be close??

 

First of all, sounds like you're not looking to make 100hp. If you're not running it over 4k rpm then forget about the hp. Sure, you can get 100hp out of an 88" but it's going to take longer cams, heads that move some air and you'll have to rev it to get there. It'll be soft on the bottom and make peak torque at a higher rpm. Sounds like your goal is bottom to middle torque. Displacement and a shorter cam is what will give you that. A big bore will give you a lot more torque than a little bump in compression from the compressors. Look at the difference between modern 96" and 103" bikes. The extra displacement gives you a little more compression at the same time and really brings the torque up. Flat top 95-98", .030" head gasket and the heads cleaned up should bring it up over 100ft lbs easy with those 203s but a set of Andrews 48s would make it real strong on the bottom. You didn't mention a tuner, but don't skimp on a good tune.

 

You are right I am much more interested in torque than hp.

Please don't take this the wrong way not trying to argue. Trying to grasp the concept. If you go from 96 to 103 you displacement increases but that does not necessarily mean that your compression will, right? I would think that compression is a variable just like displacement, cams, or heads.

 

I'm not trying to hijack this thread, but just trying to clear up something. I am also looking into helping my '06 FXDL by adding the 48's now and then doing the 95 or 98 bore later with compression set at 9.5-9.8 then. I was told the 48's would be great for bottom-mid range torque now with the stock compression, but if I did the BB that I would need to replace the cam, that it doesn't like the compression bump. Is this correct, or will the 48's handle the compression bump from stock? I don't want to build a high comp motor with the gas problems around here, just want to keep it at 9.5 / 9.8 max.

 

The compression increases with the displacement. A stock flat top 88" is rated at 8.9:1, stock flat top 96" 9.2:1, 103 is 9.6:1. You can raise or lower the compression using domed or dished pistons or making the cylinder head combustion chamber larger or smaller, but the displacement itself also has an affect on it.

Too much compression with a short torque cam will result in higher cylinder pressure and heat, starting and detonation issues. I wouldn't be going over 10:1 with a 48 but I wouldn't hesitate to run it in the 9.5-9.8 area. Plenty of people running them in 9.6-9.7:1 103 baggers with no issues.

 

Thanks, i was wondering why the 48's seem to do so well in the 96....didn't know comp was at 9.2, thought it was a little higher, closer to 9.8.... think i'll go ahead with the BB later and plan it at 9.5 or so. Thanks again for clearing this up for me.