cams and rockers

[Bain]

I have a couple of questions if anyone can help me out.

First I am planning to buy a pair of heads from jegs and the rockers required for them come in two different ratios, so my question is what are the ratios actually refering to and how should I go about choosing one or the other.

My other question was on cams since they have so many different cams as far as mechanical, hydrolic, roller and so on. Why couldn't you use hydraulic roller lifters on say a mechanical lifter cam?

thanks for the help.

[rdobbs]

the ratios refer to lift. a 1.6 ratio will give u about
10 % more lift than a 1.5 ratio. u must have the
proper springs and push rods. always match cam
with lifters or you will have trouble.
rdobbs

[quaddriver]

rocker ratio is a cheap way of increasing lift. std ratios are typically 1.5:1, if you increase ratio you have to worry about coil bind (imagine a spring compressed so all the coils touch....then compress a little more) and worry about valve/piston interference.

a roller lifter on a non-roller cam will wipe out the cam - it is too soft.

you can have solid and hydrAUlic roller cams and non roller cams. but you should not mix and match.

also you have to watch that you do not put a non roller cam in a block made FOR roller cams - non roller cams have the lobes offset from the lifters to cause the lifters to spin. you do not want roller lifters to spin so either the cam has to have to lobes in a different place compared to a non roller cam, or the block is cast differently, take for example the new chevys - no provision for a non roller cam exists.