There are of course a few things I am generally ignorant about, or have never never had the opportunity to really learn. (There’s also the stuff like electrical work that I just downright hate.)
Air-cooled rocker arm geometry, as it applies to the valve train as a whole, is one of those areas I’m somewhat clueless about.
I’ve always run stock 1:1 ratio rocker arms and stock cams, so the new engine build is really my first opportunity to learn.
I may transfer the stock rocker arms onto the the car for engine break-in, but I decided to buy one of those adjustable pushrod measuring tools and learn the whole rocker arm geometry game.
I’ve been reading up on the topic and have been watching a few vids. It generally doesn’t seem too complicated between shims and custom rod lengths to ensure the valves and lifters are properly aligned and in synch.
Of course, given the costs of the uncut rods, I’ll need to make a committment to either the 1.25 or 1.4 ratio ones since I don’t intend on buying more than 1 set now.
You can already hear some rod/rocker/valve clatter from the stock setup and apparently, as you go up in HP and higher revving cams, you need to increase up to steel or chromoly rods, which increases the noise. This I did not know.
CB Performance offers a set of what they call Aluminum Super Duty Push Rods that are treated to allow for use with dual springs and such, allowing for a quieter engine. I may look into those. We’ll see.
Some Text Sources
Setting the Valve Train Geometry
Hot VW’s – October 2005 – Setting Rocker Geometry
Engine guts 13: Setting valve geometry
Bob Hoover’s Blog Valve Train Geometry
Gene Berg – Why a Ratio Rocker Arm?