As the title states. I currently have 1.52 ratio Comp Cams Pro Magnum rocker arms. To tell you the truth, when building my motor a while back I'm not sure why I didnt order 1.6 ratio. Lately I've been wondering if I'm not giving up some power becuase of this. So, do you think I'd actually notice a difference? The only difference would be the ratio since I already have full roller rockers. The car is 99% street car but not a daily driver at all. If I get the 1.6's it will be a month or two atleast as I have enough projects going on right now that need to be finished.

The basic specs of the motor, if it matters are:

357 C.I.
Canfiel 195cc heads (straight out of the box) with 2.05 intake
Flat top pistons
10.5 - 10.7:1 C.R.
Comp Cams solid roller cam 236 @.050" .550 lift (assuming with 1.5 rockers) 110 LSA
the rockers mentioned above
650 Mighty Demon carb.

Edit: Just realized I posted this in the wrong section. Mods feel free to move the general engine tech section.

 

It's really not worth the cost just for 15 horses, plus it'll go through springs faster.

 

Alright, thats what I was thinking. If its not a decent increase I'd rather put the money somewhere else.

 

Going from a stamped steel 1.5 rocker to a 1.6 roller rocker will be a slight gain but hardly noticeable.

Going from a 1.5 roller rocker to 1.6 roller rocker will normally gain you 5hp. Not noticeable.

Using 1.6 rockers is really just a poor mans cam swap. It gives slightly more lift. The duration increases but not enough to be noticeable. There are other things to consider when using 1.6 rockers. To get that ratio, the pushrod is relocated towards the rocker stud. The distance from the rocker pivot to the valve stem won't change so to change the ratio, the pushrod distance needs to change. Clearance in the head needs to be adequate. With aftermarket heads, there's normally enough room.

Since you're already going to get .550" lift with 1.5 rockers and flat top pistons, I wouldn't recommend 1.6 rockers without knowing if you'll have any sort of clearance or geometry issues.

 

I know I have the clearance between the valve and the pistons. I measured that when I put this new cam in a year ago or so. Being a solid roller I have, I guess if I ever get the car to a dyno I could always play around with valve lash. It's really not worth it to me for just a few horsepower. I guess maybe when I have everything else done on the car and there is nothing left to buy. But does that day ever really come

I'm glad the two of you agree that its not really worth it. There is just a part of me that always wants the best, regardless of wether I'll ever actually need it.

 

Piston to valve clearance is only one issue.

The increased lift of the 1.6 rockers can cause valve train issues. Will the valve springs go into coil bind with the increased lift? Will the bottom of the spring retainers hit the top of the valve guide/seals? Will the pushrod length need to be changed to keep the same geometry?

Increasing the rocker ratio does serve a purpose. It can give increased lift to a flat tappet cam when the ramps are maxed out for the flat tappets. Using a roller cam with it's more aggressive ramps can out perform a flat tappet that uses 1.6 rockers for the extra lift. Using 1.6 rockers means you can use a cam with a larger base circle to get the extra lift. High lift cam lobes are all the same height. Lift is created by how much is taken off the base circle which creates the difference between the base and the top of the lobe. You can't increase the height of the lobe for more lift because it won't fit past the cam bearings when you install it.

So instead of getting a small base circle cam with high lift, you can get a regular cam, use 1.6 rockers and get the same lift. Sometimes with larger stroker kits, you have to use a small base circle cam so that the con rods don't hit the cam.