Looking at a big bore kit for my '04 FXSTB. What is a good compression ratio to aim for with SE211 cams and minimal head work? The one I am looking at is 10.25-1. Is this too high? I don't want any pinging issues or have to go with compression releases.
GTEEZ
211's love compression, the SE cast 10.25-1 is spot on for that cam. You could even whack on a 0.030" HG on as well to give it a bit more comp. No need for comp releases unless over 190psi cold cranking. To double check this go to bigboyz website & under calculators/twin cam displacement, type in values you want.
Great info. The guy recommended a 40 thou HG to give the 10.25:1. I will check out the other site to be sure. Was thinking (from reading heaps of info) that maybe only the intake valve would need to be increased in size a little. I will be porting and polishing the heads myself. Should work out to be a relatively cheap budget build then onto the dyno. Not that it is important but they fine tune it a little.
Is your bike Carb or EFI?
i ran Andrews 55G cams @ 10.25:1 comp & my cranking was 210pound no comp releases but i still think they are a good idea, & i run them now.
in the US they use different fuel than we do and they have a different way of measuring octaine, so hard to really compare there advice. i cracked the skirt on a wisco forged piston, runing that comp with the 55's on 98 octain. but did a lot of hard k's.
my advice is if you want to run that type of compression on street, with a Carb convert your primary ratio to the lower 3:37 it makes life easier on your motor.
just a note a friend got a lot of different cams to test and dyno, he used the SE 204 then the SE 211 there was only 1HP difference between the two cams. that was in same motor useing stock heads stock bee hive springs EFI
Bike is a carby job. I already have the 211 cams so don't really want to buy some others. Do most people use the push button type releases or electric? I have a push botton one on my chainsaw the same as I have seen on the net fitted to a bike. I could easily fit those if really needed?
They say they can accomodate a 2.1 intake and are 0.050" deeper. I am unsure on whether to fit the compression releases. Also unsure about changing the primary ratio in relation to compression?
Cheers all.
