Solid 1.25:1 Rockers and Geometry

I'm replacing my stock rockers because the spring washers keep breaking. Apparently that is somewhat common with a 1915 and/or high RPM's.

I've decided to go with a CB Super Stock Rockers and with a 1.25:1 ratio (http://www.cbperformance.com/catalog.asp?ProductID=92) as it has some benefit and apparently no drawbacks. I have some questions about geometry and push rods.

1. After reading about setting the correct geometry, it sounds complicated, is it really?

2. Some things I have read makes it sound like I'll have to modify the push rod length. Is that the case with 1.25:1? I have a stock cam and as far as I know, stock heads.

The internet is a great source of information, but it also provides a lot of conflicting information. So anyone who has some experience with this, I'd love to get your advice.

Thanks.

Cole

Cole..... I'm not a valve train guru, but the stock length push rods are used in most 1915cc engines..... Push rod length becomes an issue when the engine uses a stroker crank, (and the heads are moved out,) or when the cylinder heads are cut radicly to boost compression.

When setting up, you want the adjustment screw to contact the center of the valve stem at half lift, or a little lower.... You will find the screws hit off center, front to rear.....This is done to help spin the valve during operation.

Take note of existing shim positions and location when removing the existing rockers....

Good luck...

Cole....

Ideal rocker geometry is... when the rocker is at half-lift, the adjuster screw on the rocker should be PARALLEL to the valve stem. This is achieved by changing pushrod length, AND/OR shimming the rocker assembly. This process is not difficult, just mock it all up, and get or borrow a decent dial gauge, so you can tell exactly when the cam is at half-lift. If it is not far off, you can shim the rocker assembly. Investing in an adjustable pushrod is the best 25 bucks I have ever spent. This is used to find the ideal length pushrod. When the ideal length is found, you can bring the whole pushrod to a machine shop, along with your "cut to length pushrods" and have the shop cut them to this length.

It does NOT matter what the size of the engine is. Anytime the original components of an engine are altered (eg...flycut heads, new cylinders, case being decked, new cam) the rocker geometry should be checked. If it is not. The engine WILL run, but the chance of premature valve guide wear is a lot greater, due to side loading of the valve traveling in guide.

Mike