Autolite 63?

Well, they get a little ashy with time, either a small leak in intake gasket but most likely some loss in ring tension over time (gaskets replaced once on intake). Uses a quart of 15w40 every 600-800 miles. Runs great and no misfires, very smooth. My thought was the cooler 63 number is used to help mitigate any detonation risks at high RPM if the fuel charged is leaned a bit from oil burning.

My other 318 with 46k since rebuild and XE268 cam and open chamber stock heads uses no oil at all and runs Autolite 66s. Runs good with those, but again slightly lower static compression and no oil burn.