BoomerBob
New member
Marvel Mystery Oil works good at cleaning up stuck gunk. When grabbing a motor for a swap and they've been sitting for a while sometimes they will have valve tap knocking n stuff. Getting some Marvel Mystery Oil in the intake, fuel tank, and crankcase will take care of it and loosen things up. Scrap yards will tell you this if you call and complain a motor you bought from them is tapping.
You can probably get away with using MMO on these old engines but I'd avoid it on anything made in the last 10 years. YMMV, FWIW, JMHO. It's a good product IMHO. I have a bottle of it in my garage too.