off topic - monopoint LPG

[jgra1]

hi all, I have an old fashioned LPG system fitted to my chevy, just was pondering a few things..

the lpg is fed into the top of a 4 barrel carb, and must just get sucked into the venturi's and down into manifold and engine..under load..

Is it likely the the amount of lpg is varied according to manifold vacumn? I cant see how else it's possible to get the right ratio of oxgen to lpg otherwise.. also, if you were coasting, and the lpg supply was full, it would quickly fill the carb and then leak out of the air filter and be a bomb..

following on from that, would the original fitter have 'trimmed' the lpg output, so that at given revs, a known quantiy of lpg is being used ?

I can't see a vacumn pipe going to the evaporater and was just wondering what controls the flow of gas...

thanks for any comments
john