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S & S 570 cams

  • Ratbob
    Ratbob
    5 years ago
    Hi RMAC, did you or a previous owner fit the 117 kit?
    Cams, horrid subject, so many variables.
    You mentioned you were happy with power and torque and don't wanna fuck with compression, so are you looking to start the torque earlier or keep it where it is and move only the power to the left effectively reducing the power band by having the power peak earlier?
    As you know, Harley specs show the original SE255 cam in the 110 giving slightly better low speed "torque" performance than the SE259e in the 117 kit but the old 255  runs out of puff by 4,500rpm
    As the S&S Cam has an intake closing of 40 degrees, 7 degrees earlier than the SE259e cam, you will get a bump in torque by way of increasing the compression.
    While I don't have all the volume specs etc for the 117 engine when you put some numbers into

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

    (try it yourself) and select the S&S 570 cam you'll see the compression jumps from 9.82:1 up to 10.15:1.
    The S&S cam has a touch less lift than the SE and a different duration share so I'm not sure how that will show up in riding, I'd say it will drop the power slightly off the top, could be wrong.
    The S&S cams are easy start which opens the exhaust valve slightly during start-up so as the 117 has automatic compression releases built into the heads, I'd turn them off in the tune, not sure what would happen if both release systems were running.
    Did you read what S&S say about the 570,
    "Designed for 88 to 96 CID engines with compression ratios between 9:1 and 10:1 this cam will provide a nice power increase across the entire power band. 3200-5700 rpm."
    So based on that it might not have the desired effect.  S&S have a great video about cams, worth a look if you're not familiar with them.
    Did the person who recommended the 570 have experience with that cam in a 117?
    Just had a thought, you can move everything to the left by using the existing cam and installing a 4 degree advance key.
  • speedzter
    speedzter
    5 years ago
    Has it been properly tuned ?
    Do you have a Dyno sheet to share ?
    The Se259 should work really well if tuned properly, should see an easy 100 ft/lbs + by 2500.

    The S&S 570 would be a waste in a 117, way too short, and likely have to pull a bunch of timing.
  • speedzter
    speedzter
    5 years ago
    Nothing really wrong with that sheet, maybe a bit more in the tune, maybe not !
    I think the issue is the compression is just too low ( around 9.9:1 in theory) for the 259 to really shine.

    You have two choices, pull the heads and raise the compression ( milling, good valve job and head gasket) , 
    or change cams and lose some top end.
    Bolting in a set of Tman TR625's ( or similar) would likely achieve what you want.
    The cost would be similar, but also their are better choices than the 259's .
    I would pull the heads.
  • Ratbob
    Ratbob
    5 years ago
    Quoting speedzter on 07 Mar 2019 10:54 AMedited: 07 Mar 2019 10:56 AM

    Nothing really wrong with that sheet, maybe a bit more in the tune, maybe not !
    I think the issue is the compression is just too low ( around 9.9:1 in theory) for the 259 to really shine.

    You have two choices, pull the heads and raise the compression ( milling, good valve job and head gasket) , 
    or change cams and lose some top end.
    Bolting in a set of Tman TR625's ( or similar) would likely achieve what you want.
    The cost would be similar, but also their are better choices than the 259's .
    I would pull the heads.

    Hi Speedster, if 9.9:1 is too low for the 259e, what ratio do you reckon would be best ?
    As a cheap option I was thinking RMAC could just advance the 259 by 4 degrees but I reckon it’ll only raise the compression to 10.1:1.
  • speedzter
    speedzter
    5 years ago
    Minimum (static) compression for the 259 to work well is around 10.5:1 (would go as high as 10.8 with a spot on tune)
    There is a saying , advance 2 deg OK, advance 4 deg, buy another Cam !
    Advancing 4 deg really starts to mess with exhaust timing.
  • robots
    robots
    5 years ago
    Good graph; start thrashing the bike a bit more as you might find it is actually okay
    Drop a gear, or get into higher rpm as you ride around .
  • Ratbob
    Ratbob
    5 years ago
    Quoting robots on 10 Mar 2019 03:06 AM

    Good graph; start thrashing the bike a bit more as you might find it is actually okay

    Drop a gear, or get into higher rpm as you ride around .

    I test rode a hotted up Breakout recently, can’t recall the ‘stage’ or kit, hi comp pistons, throttle body etc, but with SE266 cams, you’re right, I had to thrash the fucker to move, problem is by the time you get it on the cam, you’re way past speeding ticket and I found it became tedious, dare I say boring. 
  • spacewolf
    spacewolf
    5 years ago
    RMAC is right, the 259e (in riding) is a fairly late cam. Lined up against a tuned 110, the 110 will pull at the start but the 117/259 will eventually run it down and run away from it pretty convincingly (My Slim S 117 vs a mates LRS110).

    I did flirt with changing to an S&S cam, Andrews or another HD cam, but in the end just thought fuck it, I can ride the later torque curve out to get over the 110.
    My real issues start when I have to race the wife's LRS 117, the LRS engine is a different beast to the Slim S engine. The LRS 117 is a wee bit later again than the Slim S 117, so I find myself changing earlier than I normally would in the rev range to force her into the late drop on the curve.

    I haven't bothered in the end, it's a good motor the 117, and the less you keep opening it up the less likely you'll have issues with it later on.
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