i was reading a magazine recently (forgot which one), but some guy wrote the magazine and stated that he was putting certain piston's and cam's in his car, they magazine replied that if he went too aggresive with the cam it will lower his compression. i don't doubt that the magazine is right, but can someone explain this to me in lamen's terms.

i'm curious because i am starting my engine build soon. i am going with p13 or p30 pistons and skunk s2 or pro 1 cams. these seem to work well with other people out here.

 

what you are doing doesn't matter for this, and the magazine was trying to sound smarter than they are.

go look up static and dynamic compression

 

that magazine is correct, a very aggressive cam with big primiars will show a lower compression on a gauge, but it is not really lowering your compression.

 

It has to do with valve overlap or lobe separation angle. More overlap=more compression bleed off . Less overlap=more compression contained, to put it very simply. That's why the hot rods with rumpity cams dont idle for **** but make a ton of HP at the upper rpm range. Lots of overlap to move the powerband up. But the trade off is pissy low RPM performance.