Originally posted by taqu@Feb 17 2005, 09:51
For 4G13/15, cam duration around 260 degrees is the highest u can go without any side effect (eg bad idle, weaker bottom-end etc). Powerzone camshaft is around 260 degrees. No need for adjustable cam pulley or re-adjust anything else, just plug&play.
Going into 270 degrees & above will require changes to ur ignition timing, and probably adjustable cam pulley to advance/retard ur cam phasing. U'll need to increase the ignition timing at idle to at least 15 degrees.
For carb, u adjust the initial timing by adjusting the distributor, unfortunately, adjusting the distributor over 10 degrees can make it much harder to start the engine. So for carb u got no choice but u have to set the idle RPM higher (280 degrees and above requires at least 1500RPM to idle properly on carburetor). For injection, u can adjust the timing at idle via re-chipping or piggyback or programmable ECU (it won't effect ignition timing used for starting the engine), so idling for hi-cam on injection engine can still be nice & smooth.