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Seized J13


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I just bought a ‘68 520 with a seized motor. It sat outside for 15 years in Spokane,Wa. Hood closed, motor complete.


My plan is to pull the plugs and spray/pour “something” in and let it soak.

What “something” should I use?


PB Blaster?






Marvel Mystery Oil?





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It really depends on if it was seized before it was parked and it was towed there, or if it seized because it was parked, normally they don't sit that long unless they did not run and drive when they were parked.

Ya basically what wayno said...

why is it seized is the question....

Hopefully it's seized by the piston rings then something like pb blast down the spark plug will work. try looking in the cylinder through the spark plug hole with a flash light, the cylinder walls might give you a clue....

if it's something in the bearings disassembly is the only way you'll free it up without problems....

Either way you'll probably wanna pull the motor and inspect the bearings and cylinder bores and freshen up whatever was stuck...

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If seized then someone tried to start it and found it so. If it was running when parked and the hood kept closed the most likely thing is a leaking head gasket and cylinder(s) rusty.


PB Blaster? WD-40?  are mostly xylene and ordinary mineral oil and while they do penetrate they aren't much of a lube. Second choice and you probably already have it on hand.


Marvel Mystery Oil? is a marvel anyone buys this shit. It's re-badged Seafoam which is a whole other type of 'snake oil'. NEVER use this crap on a running engine you care about. Mostly petroleum distillates somewhat like PB and WD above but won't dissolve rust either.


ATF? Too thick takes tool long to sink in.

Diesel? I'd use this. Penetrates and lubes. And cheap

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I would let it soak a day and then try turning over by hand with the hand crank if you have one, otherwise try putting a socket/breaker bar on the balancer bolt from the bottom.

If it will not move pour more in there and let it set for a few days, then try again, if that don't work  I would try using the starter once, that might not be a good idea but what the hell, if that don't move it you will have to pull the head.

Maybe others on here have a better way, if it is rusted in any of the cylinders it likely will never turn completely, it will always jam where the piston hits the rust.

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The best rust penetrant made is Kroil, which is essentially ATF and Acetone mixed 50/50.  You can get acetone for a couple bucks at your local hardware store.  It evaporates quickly, so apply every 4 hours for a day and you'll be free if the problem is related to rust in the cylinder from the engine sitting with open valves.  A quick flashlight inspection will show you which cylinders are actually rusty - usually only 1 or 2 will be bad.  

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