Just compared a Dove rocker vs Harland Sharp... The HS's have a larger roller

[Qikbbstang]

on the valve tip. As far as I can tell they look to be similar in ratios but out of curiosity does a larger roller vs smaller roller tip have any effects on rocker ratios?

Roller Dia HS = 0.608"  Dove .500"



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[FE Jonny]

I wondered the same when I went with my T&D race rockers, it turned out the T&D did have a slightly higher ratio than the other options at the time. Ratio wise the shaft position is the determining factor more than the roller on the end.

[Joe-JDC]

Pushrod cup position is the determining factor.  Distance between fulcrum/shaft and rocker tip vs distance between the pushrod cup and fulcrum. The closer the pushrod cup is to the shaft, the higher the rocker ratio.  Moving the stand/fulcrum point closer to the valve tip and changing the rocker arm to allow for the shorter distance will also change the ratio.  Changing the rocker arm shape will also affect the ratio if the cup position is lowered or raised accordingly.  Many ways to get there.  Joe-JDC

[mike7570]

A good read on rocker arm geometry

http://www.eatonbalancing.com/blog/2007/12/