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Rocker Ratio and Tappet Screw Pitch

Posted: Sun Feb 23, 2025 9:54 pm
by Mr. V
Earlier this evening I appended to another post the subject of rocker ratio where it may have been overlooked.

I have two questions:

What is the rocker ratio of the standard pressed steel rockers in a 12G940 head? I'm led to believe it's 1.25:1. Is this correct? I have just acquired a Roebuck 'Micro' tappet adjusting tool and wish to calibrate it. This leads to the second question:

Is the pitch of a standard tappet screw 26tpi?

Re: Rocker Ratio and Tappet Screw Pitch

Posted: Sun Feb 23, 2025 10:14 pm
by philthehill
The rocker ratio for a set of factory installed pressed steel rockers fitted to a 1275cc engine which has a 940 head is 1.27.
I use a 26TPI Cycle thread tap for cleaning the threads in the rockers and a 26TPI Cycle thread die nut for cleaning the threads of the adjuster.

Re: Rocker Ratio and Tappet Screw Pitch

Posted: Sun Feb 23, 2025 11:33 pm
by Mr. V
Thanks Phil. Most helpful.