barrydidntknow

Should I be shimming this engine to run with 30% or leave it stock?How could I tell.

Chris_RC

It comes shimmed for 30%, but also includes an extra one. if it were me, and when I get my vspec I will run 30%, is I will add the extra shim just in case.

JsK

Extra shim is for break in and even then it's optional. I never use them but I
will preheat them with a heat gun for prob the first gallon or so. If you don't
you run the risk of damaging the rod.

Osirisf16

I never put the extra shim and almost always using 30% and never had problems, even in break-in.

musclecar64

I've never changed the shims in my V-spec, and I'venever had any issues running Sidewinder 30%.

Argess

Once you have it tuned, check the temps after a hard run.....if it goes up close to, or over, 300F, then you may want to consider an extra shim.