10.4:1 compression ratio Vs. low lead fuel...

[Brock Samson]

  researching my Road Runner's 340 H.P. motor shows it has a stock 10.4:1 compression ratio, being as the motor is stock will I have a problem running today's gas?..   
 

  http://www.allpar.com/mopar/mopar340.html

[deathcharger71]

that is true UNLESS its worn to the point that it leeks enough to not ping. my jet boat 327 needed higher octane until its last few years it was just so worn out that it never pinged with premium gas. but when i took it apart the exhaust valve seats were pitted big time.

[firefighter3931]

Rarely were the "advertised" CR #'s correct....most of the time they were lower. Will it run on UL premium.....who knows ; it's something you'll have to experiment with. 

Keeping the micxture on the "rich (er)" side, less timing and cool engine temps will all help to keep it from detonating.


Ron