I have an '08 Street Bob. Only performance mods are V&H Straight shots, hi-flow air cleaner, and FuelPak.

I don't have a bunch of money to spend on this and am still undecided whether or not I'm going to tear into my bike or just leave it as is. But I've already bought a few parts because I ran into a deal I couldn't pass up.

I have a 103" kit sitting in my living room, brand new in the box. It is part number 29894-07. Lists for $760 in the HD race parts book. (I got it for much less.) Anyway, it consists of the 3 7/8 flat top pistons and jugs, 255 cams, clutch spring, gaskets, and air cleaner. I don't want to run the 255 cams, and obviously I don't need the a/c. But it was a good deal. The pistons are a stock compression piston when used with stock heads as I understand it.

I don't want anything too radical, just want some more power across the board for everyday riding and to wake it up a bit.

Here's what I'm thinking;
-keep stock cams
-install 103" pistons/jugs
-have the heads decked to raise c/r to about 10:1 or so--no more than10.5:1 (and have the valve seats cleaned up)
-install SE performance valve springs
-change over to 1.725:1 SE rocker arms

The 1.725 rocker arms will give me more lift and longer duration with the stock cams. The reason I'm avoiding cam change is strictly money. I'm trying to avoid spending another $300+ for cams and $400+ or so for a different fuel tuner to accommodate timing changes. I would also like to keep the power curve somewhat where it is, just make more power across the board.

This is my first Harley, and my first engine build of any kind. I'm looking at about $800 in parts plus the head work. That's including the pistons and jugs that I already bought.
How much do I need to deck the heads to get the desired comp ratio (10-10.5:1)? And how much does mild head work like this usually cost? Would it be cheaper to buy the Kompressor heads ($600) which produce a 10.5:1 and come with the upgraded springs? Is there a way to extend the rev limit with out a different fuel tuner?

Am I forgetting anything or am I way off base here? Does this sound like a decent set up?

 

I would still do a mild cam change.

 

your not going to run the stock cams with 10.0-1 compresion,motor wont like that!! take the $$ your thinking about for the rocker arms and invest in some cams,S&S 570`s,andrews 37`s would be good choices for a milder build

 

Just me but unless you plan on racing you have made the changes that give you a little more power all ready. I would be concentrating on things that improve the handling so you can safely use the power you have already created.

But if you really want to go the 103 route the only way to get the better all around power curve is to change the cam.

 

These guys are right, you need the cam to go along with the rest of it. I would put the whole kit you have in the bike, should run pretty good. SE255's are a decent cam and you own it, so just put it in with the rest of it.

You are going to need a tune also.

 

The SE255's are a decent cam and with your combo. I would have no problem useing them and you will enjoy the difference they will make, especially if its torque you are after. Depending on what your goal is, cams can make or break motor. General rule of thumb, high lift/short duation is good for cylinder pressure. Cylinder pressure = torque. I love torque and usually stay in the 2000-3700 rpm range. The SE255's will give you very nice throttle response and when you want to get into it, nice acceleration.

 

Compression ratio of the stock 1584 is 9.2:1 ...

Just by increasing displacement to 1690, you'll increase the CR to 9.8:1 ... so, the utility of decking the heads is somewhat dubious ....

If you're going for a 'mild' 103" build ... I'd just say go with your plan using your stock heads and you'll have a streetable build with which you should be pretty pleased ....

You can do some more "what-ifs" using a calculator function on the BigBoyz website at ...

http://www.bigboyzheadporting.com/TwinCamComp.htm

Another useful site for comparing characteristics of some of the cams is nightrider.com

http://www.nightrider.com/biketech/hdcamsspecs.htm#cams

Good luck with your build ... post pics and 'how to' ... if you get stuck ask for help--a lot of guys on here have gone through it and can lend a hand ....

R/
'Chop

 

If it was me...


I'd sell that "kit".


Then I would pay a shop to bore/hone out your stock barrels for $100-150 bucks. Buy some pistons, another $150 bucks or so...go to 106-107", won't cost much if any more......

Buy some new Andrews 37's or 54's off ebay for $200 (seen them for around that, do the best offer thing).


Do the .30 Cometic gasket.....have Big boys do your heads........


and be into the whole thing for what that kit cost you and have a good 100-110 horse engine with a good tune!





Not saying the kit is bad....or the 255's are bad.......just you have better options than what comes in a kit from HD......

 

Thanks guys. I've still got some research to do.

 

I'm sure your posts are filled with good info, but I can't ever get past your avatar to read them!