oil leaking around spark plugs flat 6

The Flathead 6 (aka L Head) engines : 218, 230, 251, etc all use a 14mm Thread x 3/8" Reach Spark Plug with a Gasket Seat (Tapered Seat will not work, they do not seal on a Flathead)

The Autolite 306's that were mentioned earlier are one of the correct plugs for the old Flatheads (I installed a set of them in my '48 Dodge last year).


Run Straight (SAE) 30 Weight Oil in the engine, with some Zinc additive to help protect that ancient camshaft. Also a bit of Leaded Fuel mixed in with the gas wouldn't hurt either (remember, your valves are in the block. A little more involved than a simple head swap if something goes wrong). You're dealing with an engine that was designed nearly 100 years ago (and was in production for nearly 60 years) and relied on Oil with Zinc and Leaded Fuel.


Also make sure you fill the Air Cleaner with Oil as well (you can use whatever oil floats your boat for that purpose), if its dry it aint filtering the air. :D



Here's a little bit of Trivia for those who might find it interesting, But the Chrysler Flathead engines were responsible for many things production engines have today. They were the first automotive engines to have Cam Bearings. They were also responsible for the Replaceable Oil Filter and Rubber Motor Mounts too.