Hyd Roller vs Hyd Flat tappet on SM heads
I agree with you. It seems that with a stock SBM rocker shaft location, a large diameter roller tip makes the geometry worse.
The roller tip certainly changes geometry.
I know there are two schools of thought on geometry and some variations from that.
Going off my memory there is 2/3 lift and 1/2 lift, meaning at 2/3 lift the rocker is 90 degrees to the valve.
1/2 lift means the rocker is 90 degrees to the valve.
This is basic stuff Mike covers on his page.
That geometry affects how fast (or slow) the valve moves off the seat and how it moves around max lift.
The amount of adjuster protrusion will affect rocker ratio.
The farther up the adjuster is, the higher the ratio. The lower the adjust is, the lower the ratio.
I haven’t done the math to know if that changes valve speed off the seat, but at this point I don’t really care. I set my stuff up to be faster off the seat regardless.
That’s why it’s important that the right information gets out there.
If the builder misses on one or both of these parameters then you get a valve train that is not happy.
IMO it matters about what is correct and what’s not.
That’s not to say there are times where someone may need to use the 2/3 lift method.
Which IIRC is what Chrysler did, but I could be wrong on that.