jjg73

i know i am flooding this forum with questions, but i have sank some good $$$ into my car as of late. i am half way done with doing a new ring job on my 340. what is the best way to break it in??? i have heard so many different ways that my head is spinning. ive heard everything from after 200 miles you can romp on it, all the way up to 2000. what is optimal??? will be running airplane fuel since my compression is 13.1-1. thanks again!!!

TVLynn

Never been fond of doing just rings without a rebore Did you replace the cam? Break that in first.. Otherwise I would put 50-100 easy miles
1/2-3/4 throttle limit RPM to maybe 4K Make sure to vary the rpm's Use engine breaking too. Airplane fuel is what 100 octain unleaded Put some 110 VP racing fuel in it at least to get it broken in

jjg73

its already been bored over thirty. everything is still pretty much brand new in it. i think the person that owned it before the person i bought it from didnt seat the rings. i was told it was bought, rebuilt and drag raced all in a short amount of time, didnt even need a ridge ream to take pistions out, barely showed up on gauge that there was any difference from the ridge to below it. i was just worried after doing all this i didnt wanna mess it up haha i have done a few engines but hve never been around for the break in process!!!

TVLynn

did you re hone the cylinders ?

jjg73

oh ya, lol i not a total neub on engine building lol. got it all put together tonight pretty much, just having some real fun, for some reason, putting intake manifold back on lol...

duster_066

Unless things have changed in the few years since I left general aviation there is no unleaded avgas. 100LL (the blue stuff) means low lead. Also avgas octane is determined on the MON system. It's actual (R+M)/2 rating is 96, not enough for 13:1!