Can't get my engine to quit "pinging".

[Stanglover]

I tried running mine on 87 octane ethanol loaded crap gas, and it seemed down on power and ran on at shut down. It took two refills with 91 Shell (best we can get here) to stop it running on. My engine is about 9.8:1 with 13cc dish top pistons.
I wish I could run it on 87, but it simply won't.

 

[basstrix]

150ft above sea level. Couldn't tell you the actual cranking compression. It includes crate motors and rebuilds fresh back from the machine shop with new rings and pistons and whatnot.

10:1 is nothing special. There's millions of toyotas and hondas riding around every day in every corner of the country with greater than 10:1 static compression and getting pisswater 87 octane. My little scion is 10.4:1. Guess what gas it gets.

Gotcha....certainly modern, closed loop controlled engines can better tolerate low octane fuel...but even my better-half's Acura will ping on 87...no idea what it's running for CR, but it specifies 91 or better. I asked about cranking compression because it can give an indication of what the dynamic CR is...and altitude affects DCR.

 

[Tnfastbk]

just back your timing back a little and see if/when it goes away. Mark it so if no change you can put it back and look somewhere else for the issue.

 

[tony-muscle]

Agreed, 10:1 should be fine. At the end of the day it would all depend on when the intake valve closes so the piston can start compressing air, which it has to do with the dynamic compression rather than static.

I assume that it is pinging at idle with no load. Follow the recommendations here on timing. Check spark plugs, etc. You can also insert a snake camera through the spark plug holes to check the conditions of the pistons and heads. Are all the spark plugs looking the same?