Re: 351 Windsor on LPG?
you can do it absolutley properly, and go even further than Atec suggests. LPG has a higher octane rating than Petrol, and a correctly built engine can provide the same power on similar fuel consumption. I have seen engines here in Oz with over 500 hp, that burnt only 2% more fuel than a similar engine on avgas.
As atec says, it comes down to the knowledge of your installer...and yes dedicated LPG is the only way to go for full benefit.
With the right equipment, you will only reap the benfit of fuel savings.