Online: softfat

Increasing compression

  • Beads
    Beads
    7 years ago
    Hi all, I’m just doing some research trying to decide on cams for my 11 softail, it has  pipes, a/c and screaming eagle tuner. I’m just curious if anyone has bumped up there compression with a thinner head gasket and if this is an ok way to do it, or is it best to do it properly with pistons and get the heads ported to use the increased compression properly? Thanks in advance 
  • tussuck
    tussuck
    7 years ago
    A thin head gasket will give such a small (bloody tiny) bump in compression that its not even worth the effort.  Now if you were to shave the heads and combine with an ultra thin head gasket (and even thin base gaskets) then you might see a change.  It was common practice to shave 50-70 thou off Evo heads to bump the compression up a notch or so, but I have no idea on what the compression and clearance tolerances are on twinks.
  • Daggs
    Daggs
    7 years ago
    and no base gaskets on twinkies tussuck :)
  • Beads
    Beads
    7 years ago
    Thanks for the reply, After doing some more reading i have come to the conclusion there is a lot more to consider before just whacking a smaller gasket in. Best to have a desired CR and shave the heads to achieve it. 
  • Daggs
    Daggs
    7 years ago
    Yes and then it depends how far you want to go... If heads are off you might want to do some further headwork... 
  • speedzter
    speedzter
    7 years ago
    Just for your information, as a rough guide, a .030" head gasket will gain about 0.25 points of compression over the stock gasket in a 103" .
    Likely not worth doing by itself without doing other work.

  • tussuck
    tussuck
    7 years ago
    And the target compression needs to marry in with the intended cam as well.  Some cams like low compression while some run like chit unless the compression is a minimum of X:1
    The key decider is do you want low down around town torque or higher rpm speedster running?  Totally different cam and compression setups etc.

    Obviously a turbo is the best way to go, but its a bit over the top for most...lol
  • Beads
    Beads
    7 years ago
    yeah the trouble is there are so many different reviews and opinions on so many different cams and combinations I can’t make my mind up! Haha I think I’ll jist see what I can get for the best money and go from there. There is a set of se204 cams and a set of se255 cams on gumtree st the moment which I have been looking at 
  • Daggs
    Daggs
    7 years ago
    Yes but what do you want, low down torque, midrange or top end horse power? Low to midrange torque is what most are after.
    How hard do you ride? Solo or two up? All factors to consider
  • Krash Kinkade
    Krash Kinkade
    7 years ago
    I've always liked machining bottom of barrel as that brings the piston up for a Better swish..
    but depends on what cam's your using what your after. if you drop cranking pressure below 180 pound you won't make power.
    good luck with it.
  • Beads
    Beads
    7 years ago
    Mostly ride solo, and I ride fairly aggressive but don’t rev right out every gear change, I’m after low-mid range tourque 
  • Krash Kinkade
    Krash Kinkade
    7 years ago
    sometimes, the stock cam's work best, just machine some off bottom of barrel ( need to get someone who knows how as twin cams use an o ring to seal at bottom of barrel ) rase comp a good three angle valve job, match manifold to head. good flowing air cleaner. set of pipes like say super trap 2 into 1 as can tune them. and most important a day on the dyno with a tuner that knows how to make a custom map. stock cams stock tb. I think you would be happy. but hard to find a good tunner. easy to find a dyno, hard to find a good machine shop who can do quality machining. but if you can, that would give you what you want.
  • tussuck
    tussuck
    7 years ago
    Or sell the Twink and get an Evo.....SO MANY proven com and compression setups for the Evo that its AWESOME!