Bret briefly introduced the concept to me. I thought I understood it, but after seeing a few websites, i think im kind of mistaken as to how to actually measure it. It is the distance between where and where?

Also, is the only way to increase installed hieght to use shims, for a given pushrod length? Or would using valve lash caps also change it? From the way I understand what it is a measure of, it seems like a different length push rod, or using lash caps on the valve stems would alter it as well.

Im basically trying to figure out how to measure it, that way I can shoot for an ideal installed height when I order my RR's and everything this week.

 

I believe install height has to do with the valve spring. The higher that is, the shorter the pushrod has to be. Stock is 1.75" on the spring and 7.2" on the pushrod.

Works like this...that is if I am right...the spring pushes up on one end of the rocker arm, so it pushes down on the other end. The higher it is at its resting place (installed height) then the lower the other end is going to be, or the pushrod end. Think of the rocker arm like a teeter totter. The spring and pushrod have to be certain lengths so the geometery is correct. The taller the installed height of a spring, the shorter the pushrod. Smaller the spring, the longer the pushrod. That's why people say to use a pushrod length checker when you do spring installs.

That is my understanding of it, if someone else knows more, please correct me.

 

There is stem installed height, and spring installed height.

Stem installed is the distance between the tip of the valve and the spring pad, this will effect rocker geometry. Can be changed with longer valves, lash caps, and how deep the valve job is shot. A taller stem installed will mean a taller spring installed.

Spring installed is the compressed height of the spring while on the heel of the cam lobe. It is measured between an installed retainer and the spring pad. Can be changed with longer valves, shims, keepers, retainers, and depth of valve job.

Spring installed does not effect which rockers to use. That is determined by cost, ratio, and stud size.

Other important things to measure are distance to coil bind after max lift; how much more the spring can be compressed after it is compressed to it's open height. I like to see .125" but will go as low as .090"

Valve seal to retainer clearance after max lift, measures same as coil bind, and I like to see the same values.

 

Well written!

Rich

 

Thanks everyone.

Im just trying to figure out what to do so my valvetrain is correct when I switch to comp beehives, and 7/16 pro mags. I also was going to get comp hi-tech push rods for it, but I wasnt sure whether to get the stock length or not? And if I would need shims and everything...