77 Rv 340 F/A

_FIII · Post by **_FIII** » Fri Jan 18, 2008 11:54 pm

Should I run premium in my 77 Rv free air? Heard that I shouldn't...but also not to run an ethanol blend, which equals the local regular.

WatertownBob · Post by **WatertownBob** » Wed Jan 23, 2008 11:27 am

You need to find out what oct was required for the sled. Was there any mods to the engine? Also do not run any ethonal blends with out rejetting.

You will have the most performance out of the engine running the lowest oct. rating that is allowed in you machine.

Bob

427cobra · Post by **427cobra** » Thu Jan 24, 2008 12:56 pm

I've heard Shell premium is one of the fuels that does not use ehtanol.

Is that true?

basketdators · Post by **basketdators** » Fri Jan 25, 2008 12:44 am

Bob
Please explain why higher octain=less performance.
Thanks, Bill

Mr. Deere · Post by **Mr. Deere** » Fri Jan 25, 2008 4:15 pm

More Heat. the other BOB

78440liquid · Post by **78440liquid** » Fri Jan 25, 2008 5:49 pm

I was always told that high octane fuels require higher compression to burn properly. I used to work at a GM dealer and was told that high octane fuels do not burn completely in lower compression ie 8.5:1 and will produce more emissions out the tailpipe (unburnt hydrocarbons). Feel free to flesh this out Joe as you have more experience in this field. Joel.

basketdators · Post by **basketdators** » Mon Jan 28, 2008 2:22 am

Does it have to do with the speed of combustion.
Bill

WatertownBob · Post by **WatertownBob** » Tue Feb 12, 2008 4:27 pm

One way to get more power out of an engine is to raise the compression ratio. You would need to change the timming and use higher oct gas. Oct = the resistance to ignight or burn. Use low oct in high compression engine and you will have a paper weight the gas will start to burn under comperssion instead of waiting for the plug to fire it off.

Lower oct has more heat energy BTU and burns faster

High oct burns slower and cooler

So useing the lowest oct rateing that is published for a particular engine will produce the most power.

Bob