Remember if attempting to break new ground the important relationship is
not the absolute diameter of any step or jet, but the annular area calculated by subtracting the area of the metering rod (OD^2 X .7854) at any specific distance (from the tip) from the area of the jet (ID^2 X .7854).
What this means: if you find a metering rod with the step positions extremely close to what you need, and the right proportion between the WOT step and high-vacuum cruise step, a non-stock main jet size can be de-constructed from the OEM numbers.
Example:
The original jetting was .072" jet, and steps of .052" (economy) and .036" (power), giving areas of .001948 in.2 and .003054 in.2.
You can't find a rod with the sizes you need to make a minor mod, but you
do find one with .060" and .047" steps in the right places among what's available for Edelbrock, Rochester etc.
What size jet gives you the original results using none of the original sizes?
.078".
I wrote an Excel app that does this automatically, e-mail me at
[email protected] for a free copy.
