MARKUS_P

wondering if changing out 1.5 steel stamped rockers to eg. 1.6 roller rockers will make a difference.
How much HP gain?
Is increased valve lift always more HP?

1979toy

Yes, increasing the rocker ratio will incerase the performance, provided you don't have a meeting of valve and piston. How much performance is dictated by how much cylinder head and cam you have. I've heard that using roller rockers will reduce the oil temps. but I don't have any hard data on that.

QuickVet

you might see a gain of a few HP. i think 1.6 rockers will increase the lift by .30 :confused: but im not exactly sure. in other words, if you have .450 lift you would then have .480 lift.

Ace77

The difference in lift is dependant on the lift you have now.
The geometry of the rocker is different, causing the ratio of lift to jump to 1.6 instead of 1.5 .
1.6/1.5 = 1.066666... which means that your existing lift at the valve will be increased by about 7%.
Or, take your cam lift and multiply by 1.6 .
You have to know the existing geometry of your piston, gasket, and head very well to know whether the new lift will crash the valve into the piston.


[Modified by Ace77, 8:34 AM 11/26/2001]

Ganey

Between unnoticable to noticeable, maybe about 15. Divide valve lift by ratio normally 1.5 to get cam lift & multiply by new ratio. Stock measure less than 1.5 so 1.52 increases lift. Comp Cams "1.6 were made for tuning."

MIKER

I've heard of people gaining favorable results by installing 1.5:1 rockers on the intake and using 1:6.1 rockers on the exhaust. Maybe someone could elaborate on this.

john's '81 mouse

Before installing more than 1.52 lift rockers, suggest you carefully determine whether you have clearance in the pushrod slot in the head for a 1.6 ratio rocker arm. Many / most times you need to remove heads and use a special tool (I believe it's called a 'louis tool'?) to enlarge this opening to prevent rubbing / interferance of the push rod on the head.

Providing more lift / faster ramp speed of exhaust valves will make the camshaft perform more like newer technology dual pattern camshaft designs. Would probably help some. I recall conversation on this topic in the past, where some engine builders/old timers, suggested improved HP/Performance by using a mix of 1.5 and 1.6, but recall that it was based upon cylinder location, had something to do with length of intake runner and exhaust manifold passages, or something like that.

gkull

Piston to valve clearance is not a big deal unless you have bigger than 2.055 intakes and more than .550 lift.

I have always ran 1.6 or higher. The Comp Cams roller tips are the way to go on buget performance motors.

The main concern is can your existing spring combo handle increased lift. Not only look at coil bind but retainer to valve stem seal clearance. I had to use .100 longer push rods to get the valve Geometry right with production type heads with screw in studs and guide plates.