Hi, I'm from south america and I want to buy a nice 76 sedan deville that I found but I have a question about fuel milleage. I know that a 76 cadillac 500 and MPG are antonyms but what If I tune it to run on CNG?

I was thinking on a setup like this: 12:1 or 13:1 compression ratio (only CNG not gas), new HEI ignition system, replace the TH400 with a six speed 4L80E and a rear end gear of 3.53, 195 thermostat, electric fan, electric water pump.

Don't worry about the CNG tanks weight, maybe I can found lighter tanks and use two or three on that big trunk

I was hopping to get something like 10 MPG town / 17 MPG highway with this set up. Can I get this or I just only dreaming?

 

You will be able to buy a lot of gas with the money it costs do the mods. If you will only be driving I mountains it's unlikely you will hit your goal. If you are in area where roads are mostly flat possibly. Bio diesel maybe more practical.500 CID is gong to require a lot of fuel regardless of type.The 76 weighs as much as a 4wd full size truck so LS w4L60e might work easier and more economical conversion.

 

The only real benefit to conversion to CNG is emissions. It has been proven that whatever the gasoline (petrol) engine gets, a CNG (or propane) system is 15% LESS. The other thing is, a CNG system will run on LPG (propane), since propane is a component of CNG. Most of this has come from Rousch Propane, a company that routinely retrofits Ford F250/350s, E250/350s, and commercial chassis to run on Propane (GM does not have that "luxury").

TS

 

I live on a hilly city so mostly of the roads are not flat. Diesel is not an option because I consider that the sound, smoke and feeling of that kind of engine is an antonym of the cadillac smoothness and luxury

on my country the CNG retrofit is very common and doesn't require any permission, I think will be better to have two CNG tanks in the trunk and the caddy as a daily driver than a gas tank and the caddy in the garage

 

I'm hopping to get something like 10 -12 MPG town / 17 - 19 MPG highway with this set up. Can I get this or I just only dreaming?
Please advice. .........