rocker arm ratio, what does it all mean?

[benno440]

whats the differences and benefits of the diffeent rocker arm ratios?

i currently have 1.5 arms would i benefit from changing?

 

[RustyRatRod]

Need more info about your motor. What are the cam specs? Cubes?

To generally answer your question, a 1.5 rocker ratio lifts the valve off the seat 1.5 times that of the cam lobe. Or at least in a perfect world it does. Things like pushrod angle, rocker accuracy and other factors also figure into the equation. So, if you raise the rocker ratio to say 1.6, you're now opening the valve more with the same camshaft. Make sense?

 

[44070dart]

usually it benefits an engine to increase lift ratio ...it depends on your cam ..going to 1.6 rockers increases lift so its like changing your cam to a higher lift type without the work of installing a new cam ..its important to know what cam you have in your engine ( to calculate valve to piston clearance ) and know that you should probably change the valve springs if you decide to change rockers

 

[benno440]

505 cubes.
stealth heads
already has beefy springs and 10 lock retainers,
•Advertised Duration (Int/Exh): 300/305
•Duration @ .050 (Int/Exh): 250/255
•Gross Valve Lift (Int/Exh): .540/.540
•LSA/ICL: 108/104
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 3000-6800

 

[RustyRatRod]

If you're runnin iron heads, keep the 1.5s. If not, you can go to 1.6s.......but I'm not sure you'll see a huge benefit. If you already have the 1.5s, I say stick with um.

 

[benno440]

good enough for me.

more was interested in what the difference ratios mean, thanks

 

[Meep-Meep]

Rusty's description nailed it. I'll add that the higher ratio will affect the opening rate as well as total lift. They can also add more stress on the valve train components too. I suppose the only way to know if they will be beneficial on your motor is to try a set and check the results on a dyno. But to me it sounds like you have a pretty healthy motor as is, and with proper tuning, you may be able to find 20 - 50 HP just by tweaking what you have.

 

[Sixer]

Not mentioned was that spring heights need to be carefully checked when using the 1.6-the extra lift may remove the safety margin that was inherent with the 1.5.

Edit-oops, see that dart did mention springs.