103" build - need opinions!!
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Road Captain
Joined: Apr 2010
Posts: 513
Likes: 3
From: Charlottetown, Prince Edward Island
103" build - need opinions!!
OK, so last year I did a 103" build on my 09' but went with stock compression and wasn't really impressed...... I believe the cams I added made the biggest difference. Anyhow I bought another ride and want to do another build. My question is should I do a high compression build this time to accomodate my tw-555's? Is the key to more power in the compression? As I see it the extra cubic inches are worthless unless the compression is bumped. Am I asking for trouble if I go this route??
It's all about your budget. IMO any 103 is worthless without head work. The stock heads are the weak link in any HD platform. Higher compression will generate better performance sure, but the most bang for your buck will be in the heads. Ideally you should have both. Head work and at least 10.5:1 compression.
HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
I agree with Harley tuner but I the stock heads flow pretty well. Having said that, you will have to pull the heads to shave some off to get the compression those cams like. With a .030" head gasket, chamber volume will have to be about 84cc to produce a static CR of 10.2, corrected of 9.35 and cranking CR of 194psi. Compression releases would be advisable. While you have them off, blue printing the heads and a good multiple angle valve job will help. Of course by the time you have spent that money, a nother couple of hundred will get the heads fully ported with larger intake valves. So, like harley tuner ways, not really worth doing unless you spend some money on the heads and since you have them off, might as well go it all. Depending on who does the work, you are probably looking at about $700-$800 for the headwork.
Road Master
Joined: Dec 2008
Posts: 872
Likes: 20
From: Niagara Falls Canada
think 10:1 is about it
look for the fuel moto 107 build post. If i recall I dont think much more than 10-1 is about it, start to get knock or pre-detonation if I recall the posts. you have a way to get higher octain fuel.
107 post had quite a bit of technical data about compression and builds.
think there is 2 posts on 107 build both about 30 pages of posts
107 post had quite a bit of technical data about compression and builds.
think there is 2 posts on 107 build both about 30 pages of posts
Road Warrior
Joined: Mar 2008
Posts: 1,783
Likes: 10
From: Oh
You didn't mention what you bought. If you are planning on doing a similar build with high compression (HC) I would suggest truing and welding the crank. I also like HC builds but, as has been said octane availablilty is another consideration. The other posts also give good advice. Good luck on you decisions.
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