UNLEADED FUEL?

[plym_46]

Old gas went bang even at low compression, todays fuel, it is only partially gas these days, goes Whooomph.  In other words when our cars were designed gas was poor in quality but burned much faster (and according to the gummint much dirtier) so todays "gas" is designed and formulated to burn longer and cleaner even at higher compression. 

I have read from several sources that old engines burning today's fuel benefit from running more initial timing advance than factory spec.  I have found my engine operates better with the timing set at 4 degrees before TDC, rather than the TDC setting speced by the factory. It may be seat of the pants, but It starts better, and get better MPG set this way.

[Wm Steed]

Tod's response is right on the mark about unleaded fuel, the old engines were built to run an very poor fuel. The one thing I would be careful about is waiting for a fuel leak to occure. The modern unleaded fuel will eat up any old style rubber fuel lines and the fuel pumps.  I would replace these items before you drive it anywhere, the possiblility of an engine fire is not worth the risk. If you are some what  observant, you have probably noticed the amount of car fires and/or spots along the road edge where car fires have occured. These engine fires are usually  the result of neglected fuel lines that unleaded fuel has eaten through.....Bill

[fine39]

Thanks for the good news.  I can't wait for the snow to go away!

[TodFitch]

Your car was designed for standard gas when you had to pay extra for "Ethyl" (i.e. lead). It has hardened exhaust valve seats from the factory. As long as your engine has not been modified for exceptionally high compression, run the cheapest standard gas you can find.

The only issue I worry about with modern gas is that it does not play nicely with older rubber. Be prepared to rebuild the fuel pump with modern diaphragm materials, replace the fuel hose with modern rubber, etc. If you don't mind a minor roadside repair, those items can be dealt with if/when they happen.

For a more in depth write up on my opinion, see:

http://www.ply33.com/Misc/gasoline

[fine39]

Can anyone give their opinion on the use of Unleaded Fuel to run my '39 (flat 6) without getting into engine modifications?  She purrs like a kitten and I would prefer to keep the engine buttoned up until absolutely necessary.   Your advice on using additives is also appreciated.