Where is the best place to ground from on the Lycoming engine? My engine is grounded from the #4 cylinder head to a metal tab attached to one of the engine mount/firewall bolts. Is this allowable? My engine just had all four cylinders overhauled and it has high compression pistons. I can only get one revolution of the starter when it is cold. Has fully charged battery with all connections checked. Grounding cable is 6 awg and battery cables are what looks to be 2 or 4 awg. Aircraft Spruce only sells the #6 cable so I am assuming the current capability is sufficient for the starter which is a light weight starter. Take four plugs out and the starter turns over fine. No drag on the engine. Any suggestions besides a bigger battery. Which I have tried.Battery is a Odessey PC680 mounted behind the seat in an Acrosport 1.