Thread: BC stg 3 cams setup

Friend has SR20DE with following parts:

10:1 SR20DE
BC stg 3 cams
BC springs
JWT cam gears
SSAC 2.5" header
Straight open 2" exhaust (will be replaced with 2.5"-2.75")
Calum ECU



Question 1: Head is milled by 0.7mm. What cam gears setting he should try? For now we are trying +2.5, -2.5.

According to JWT cam gear manual HERE milling head or block affect cam gears setting by 2.5 degree with 1mm (0.047") shave. Does it mean we should try +5, -5?
ANSWERED. Cam gears at +2.5, -2.5 for now. Will try +2.5, -5 or any suggestions?

Question 2: Another question - how to calculate actual compression ratio after head is shaved?

Come on...?

Not real sure about the head being shaved, but I think mine are at +3 -3.

i know for S3's there rated for 0',0'

That was a good read, doesn't explain if it advances or retards timing but I'm almost sure it retards the timimg. So your I-+2.5 & E--2.5 would be a good move. Going beyond that would move the events timimg further which may actually give you a bump in power at some rpm range but no way to know unless you do it on a dyno. $.02

Every 1mm shaved is 2.5* advance.

Does it mean if i shaved head by 1mm and set cam gears to +5, -5 it will be same like non-shaved head and +7.5, -2.5?

Yes. That is correct.

Thanks a lot Cliff.

Another question - how to calculate actual compression ratio after head is shaved?

Subscribed for this one too!
Any chance to assume a value for the CR drop due to use of cams (no matter jwt or bc)?