No change in cam-duration, but duration at the valve... yes there is more...

 

so whats the deal with gm's "1.7" stock rockers not actually getting to 1.7 until later in duration than aftermarket rockers?
Why?

 

It's the way that the pushrod seat is in relation to the pivot point of the rocker body, and the contact point of the valve...

With the VHP/Crane rockers I mentioned there, the PR seat is about .150" closer to the cam, and with the "floating" style adjustable rockers, it change the geometry/ratio at which the pushrod actuates the valve. The change has to do with the path the PR travels as the valve is opened.

It's really hard to explain, but it's a really simple change... You can check out some more info here...

 

nice article that should keep me occupied for at least an hour

 

I've been running the Comp Pro Mag 1.85s for several years now in a 99 Silverado that also has Comp 918s and Comp hardened pushrods ( required when using rockers that have guide plates). I like them so much I also bought a set for my new 2004 Silverado. They're not cheap and they're not shaft mounts, but they are adjustable and very high quality unit. They're rebuildable, but I can't imagine how many miles you'd have to go before they need it.

 

Did you just mount the rockers in vehicles with stock cams?

 

I use 1.8 Harland Sharps with my Comp 216/220, It all depends on the ramp speed of the cam.

 

mattrem,
On that cam whats the difference between lift at .002 and lift at .05
did you do rockers with the cam?

 

Let me find the cam card I will get back to you. Actually I put the rockers on before the cam. Then I picked a cam that would work with the rockers, this cam is supposed to like the 1.8 rockers. It is really strong.

 

In both cases it was an aftermarket Comp comshaft being used with the 1.85 comp Pro Mag rockers. The cams were ground for 1.7 stock rockers so the higher ratio rockers provided so additional lift (approx. .030).