What Cam is what?

[Dod]

I've a 270 deg Cam, i'm told to use the 285 item, whats the difference? Is it to do with the power bands?

[Adam]

The 270 one has 270 degrees, and the 285 has 285 degrees.
I think the 285 one will make the idle more lumpy, and alters the powerband but i ain't an expert so ain't 100%.

[benji]

lol. you can always tell when someone don't have a clue what they are on about.

the 285 won't be lumpy. mine isn't, jims 300deg isnt, dan's 290 isn't, and i'm sure there are loads of other people who will tell you the same.

what engine is the 270 cam in?

[Dod]

Its in a 1400 spi with a ported head and a 4 branch. How does it benifit the car and how do bigger (290, 300deg etc) cams do the same?

[benji]

basically (very basicall), it works by opening the valves more(bigger lift) and for longer(bigger duration) so you can get more fuel/air mix in and out quicker. the bigger the duration the more that gets in, same applies to lift. the thing that causes lumpy idle is overlap, this is when the inlet and exhaustvalve are open at the same time. while being ok at high revs it causes a lumpy idle. so the bigger the duration the more overlap you get. but on these engines it is not mormally a problem.

on a spi engine i would recommend changing the head to a sri one instead of changing the cam from a 270 to a 285