Rocker Arm Geometry Question

[CAJUN C4]

I'm going to 1:6 Roller Rockers on my 95'.My friend suggested we might have to put different size push rods in because the higher lift may change the geometry. I wouldn't think that little more lift would change it that much.?
Agreed????

 

[JAKE]

No, a change in pushrod length won't be necessary. Going with different ratio rocker arms, if that's all that's changed, doesn't effect the pushrod length. However, your valve springs become an area of concern.

Going from 1.5 RRs (which in actuality would probably be in the 1.4x area) to 1.6 RRs (which will be much closer to 1.6 RRs) will cause about .030" valve lift.

What that does is cause the valve springs to compress more by about the same amount. Since most stock valve springs are pretty close to being maxxed out on how much lift that can safely handle, the 1.6s can push them over the limit.

It's best to go with better springs when moving to 1.6RRs from 1.5s, especially if the performance increase you'd expect can be realized as the top of the RPM range.

Just my thoughts.

Jake

 

[JAKE]

Here's another thought:

With the valve in the fully closed position, you should have about .060" clearance between the UNDERSIDE of the rocker arm and the valve retainer.

You can take a paperclip (measure it's thickness to see if it's at or very near to .060" thick) and use it to stick under the rocker arm to check for the needed clearance.

Normally you shouldn't need longer pushrods going from a stock to a Hot Cam but it pays to check.

There's GOT to be something causing this excessive noise; now it just becomes the job of finding it.

Jake