VIPRETR2

iTrader: (63)

I've been looking around for guys using close to .600 lift cams and X-ER lobes on 918s. I'm told for these types of cams you should shim the 918s close to .050 from coil bind. The problem lies in the actual compression to reach coil bind on a 918 spring. I see this info thrown around alot on here..

Outside Diameter (O.D.): 1.290"/1.060"
Inside Diameter (I.D.): .885"/.656"
Installed Pressure: 130 lbs @ 1.800"
Open Pressure: 318 lbs @ 1.200''
Coil Bind: 1.085"
Maximum Lift: 0.625"
Rate (lbs/in): 313 lbs/in

Although this is the info on the box of 918s I just received..

Outside Diameter (O.D.): n/a = not on box
Inside Diameter (I.D.): n/a
Installed Pressure: 130 lbs @ 1.800"
Open Pressure: 318 lbs @ 1.200''
Coil Bind: 1.140"
Maximum Lift: n/a
Rate (lbs/in): 313 lbs/in

and this is the info directly from Comps website...

Outside Diameter (O.D.): 1.290"/1.055"
Inside Diameter (I.D.): .885"/.650"
Installed Pressure: 130 lbs @ 1.800"
Open Pressure: 318 lbs @ 1.200''
Coil Bind: 1.1"
Maximum Lift: not listed
Rate (lbs/in): 313 lbs/in

So I guess the real question is, which values are correct? I would think that it would be best to use the figures printed on the box? On a side note, I have been advised to use a dual spring for X-ER lobes with this type of lift, and I might, but I would still like to get a definitive answer on this subject. Thanks,

Larry

Studytime

iTrader: (15)

Which values are correct? Something tells me to believe the results you got from actually measuring. That seem to coincide best with rational thought. Why wouldn't you believe those values?

I personally would not be comfortable running .050" from coil bind, but if you are that's up to you. I agree with the idea of running a dual coil spring with the XE-R lobes. Sure they're being run daily on 918s, but a dual spring sounds like a much better alternative.

Ben T.

VIPRETR2

iTrader: (63)

Either your reading the post wrong or I confused the wording. The first set of values is used on LS1tech alot, the second set were printed on the box of 918s, the third set is directly from Comps website. I haven't opened the box yet. I'll most likely run duals if I go with a cam with the aforementioned qualities, I'd hate to ruin my lightweight LS6 valves

Studytime

iTrader: (15)

I was under the impression the second set of values were empirically derived. Taking them to a local shop would be the best bet. They can check coil bind literally in two minutes if their schedule permits.

Ben T.

VIPRETR2

iTrader: (63)

True. The internet is making me lazy Thanks for the input.