Originally Posted by lil-bump

Not sure about the 353. but I measured my 3SCT tuned and with no shims; it has a real head clearance of a .30mm so for 20% i would add .15mm shim. the engine comes with a .30mm shim. I install this for 25% which gives me a total head clearance of .60mm. A little fat for 25% but better to be safe.
Adding .40mm of shims would get around .70mm head clearance this is a little too much for 20% your low end will suffer.


Pass you soon...