Rocker Arm Geometry
Turbo Mini Forums

I'm looking at making a set of roller rockers for my 998c turbo build. Probably not the most nessecary component but I think it would be a swell design project. I measured up my stamped, stock rockers last night and thought I would share some of the geometry since I haven't found it easy to come by.
I used a comparator to measure the part by place the push rod and rocker tips on 1-2-3 blocks and then adjusting so that the center of the rocker shaft was in the same line. This is the proper setup for the rocker according to a number of sites but this one in particular was very helpful.
http://www.flowspeed.com/rocker-tech.htm

Setup on comparator:


Measured geometry. The main thing I am interested in is the overal length. The measure rocker ratio was around 1.25:1.
(L=2.1304, Rod->Push=.9502, Rod->Valve=1.1802)


Using a 1.3:1 rocker ratio and the roller size from Titan, here is what I come up with (holding length constant.)

Edited by seahuston on 21st Nov, 2013.

Not sure if you are asking or telling?

The roller tip CL, pivot CL and bottom of the adjuster ball ideally need to be something like horizontal at half-lift, so are you saying the 1.3 Titan is not?
If I was designing a set of rockers, and wanted to keep other parts like the rocker box, pushrods the same, and use the same valves in my current head the same, I'd start by measuring and establishing the top plane of the head as baseline, and defining (for the cam I am choosing) the place where my pushrod top(s) sit at zero, haft, and full lift. Then establish the zero height of your installed valves, add in the positions of the various bolt holes you have to avoid, the size roller you'll use for the tip, and everything else will fall into place surely?

Yes,
Just giving information. I found some of these dimensions quite difficult to come by on the internet and figured I'd share where I'm at.
The second drawing shows the dimensions for an ideal 1.3 rocker assembly. I only put the ball from the Titan as a reference.
I'm going with a slightly different approach by measuring the rockers directly. I imagine that my pushrod length may need to change or I might need to shim my rocker stands.