I would think that they would increase the apparent lift of the cam, giving a relatively cheap alternative to a cam swap, without having to tear down the motor.

Are they a good mod for a 305 with a 'peanut' cam ??(4500rpm)

 

You hit it right on the button. They claim that you can gain from 10-20hp. I have a set for sale the crane Magnum roller tip 1.6 that only have 2500miles on them. I'm asking 125 plus shipping. I was going to use them on my new engine but the 1.6 rocker ratio and my new cam would create too much lift for the springs on my heads so I decided to sell them.

 

You won't get as much power as a cam swap though. You need higher lift AND duration to make good power.

 

I put 1.6 rockers on a relatively stock/mild 350. My times & speed changed exactly - zero.

82 has it right - it's a combo of lift and duration that has the greatest effect on power. There's a lot more to it than that, of course, but 1.5 vs 1.6 is not the same as a cam change.

 

Lots of people think adding 1.6 rockers is an automatic hp increase,it's not. There's other factors involved like how much air a given head will flow at a given lift.

 

Okay, so I understand what lift and duration are in concept, but what does lift do versus duration?

 

It all has to do with when the valves open and close.. I'm sure someone could explain ti much better than me. When you choose a cam, you should match it to your intake, meaning if you have a tpi, you want a cam that will max out at aprox 5500rpms. YOu would not want to put a huge cam that made power up to 7000rpms because the tpi would choke at about 5500rpms. As far as the 1.6 rr, they will give you performance because they increase the lift, hence, more air flow. If you have very restrictive heads, then the gain will not be very noticible and gains from a cam would not be as dramatic either. If you are looking for more power, Heads are always the best spend cash. AFR''s are the best but most costly, Trickflow's, Edlebrock, etc... But the rolller rockers are the quickest and easiest to put on your car