We have been gearing up to replace a 1970 351C that had major issues with another 1970 351C that overheated last year on the road, it got so hot it shut off & that's the way we left it. We thought it siezed up from a lack of water(leaky radiator). Anyway the other night I checked the motor out & there was no water in the oil-good(head gasket ok, maybe?). Ok, then I went on to turn it with a giant breaker bar & it turned over very smoothly, good. But, I noticed that all the spark plugs were still in & it should've been a lot more effort to turn. I'm very curious, I haven't flipped it over to remove the pan yet(it's just sitting on the ground)to look at the innerds-rods, crank. Any input on to why this thing turns super easy with the plugs still in? Thanks...
Sounds like your rings are gone, or timing chain is broke in the wrong position;that is with most valves open.Maybe collapsed rings ,or seized rings. Pull distributor cap and turn the motor thru . The rotor button or distributor shaft should turn through smoothly. Pull all spark plugs and do compression test. Hope this helps.
If it was that hot the rings are likely done. The lose their tension against the walls. Likely stopped running when the piston skirts seized into the bores. After they cool completely they break free again sometimes. My guess you'll find some nasty looking piston skirts when you tear it down.
i would just put a comp.gauge on it and see what the cylinders have.pull the valve covers off and make sure everything is playing nice and go from there.
Thin piston tops on these! Could've blown holes right through them! Take a decent flashlight and peek through a plug hole with the piston almost at the top. Regardless, any engine run that hot may need a total overhaul!
