Hi LG,
If you can set your regulator to just below zero (With respect to local atmospheric pressure.) then you would not need the regulator. My understanding is they regulate to about zero pressure so that the gas only flows into the carburetor when the pressure in the carburetor is below zero. (The same way it would suck petrol up from the float chamber.) I would imagine that you would feed the gas pipe into the carburetor at near the smallest diameter point.
Les.
Hi Les,
That's more or less what I was implying in post #2.
For safety though you need a master gas cut off valve which automatically shuts the gas off if the engine is not running.
The modified standard gas regulator that I mentioned controls the gas pressure according to inlet manifold depression, so you need a connection to the engine's inlet manifold down stream of the throttle.
The regulator then controls the gas pressure, and hence gas flow, inversely proportional to inlet manifold depression (a lightly loaded engine has a high depression and a heavily loaded engine has a low depression). This same principle is used on constant depression carburetors, like SU and Strongberg. You tune the gas system by the size of the gas jet aperture and the tension on the regulator spring.
Just a few points about running engines on gas:
Gas does not need to be atomized and and mixed with air- this is one of the major tasks with liquid fuel.
Gas ignites more easily than liquid fuel
The engine runs cleaner because there are no condensates on the cylinder walls.
But, gas has a lower calorific value for a given volume, so the engine will not be so powerful.
spec
PS: Rolls Royce run their car engines in using gas.
spec