need more fuel

[Robert W. Hughes]

> I guess if you go for the shim the regulator will stay air tight but you
> need a bit of trial and error to get it right since you don't know how much
> is needed to increase pressure 5psi (for example).

You can calculate shim thickness with good results like this:
1. measure present fuel pressure
2. disassemble regulator
3. measure free length of spring
4. measure compressed length of spring by measuring spring space in
housing
5. SpringRate = fuel pressure/(free length - compressed length)*
6. shim thickness = (desired fuel pressure - present fuel
pressure)/spring rate

In my case ordinary galvanized roof flashing with .015 thickness
produced 5psi increase exactly as predicted. Be very careful
re-assembling the regulator. The screws will try to grab the diaphragm
and twist it and apparently no one sells the diaphragms separately.

* I know, actually this isn't the spring rate but it is related and it
is the number you need here.
-- 
Robert W. Hughes (Bob)
BackYard Engineering
Houston, Texas
rwhughe at hal-pc.org