Unstuck a Stuck Engine

[JimS123]

I've gotten stuck engines running again in the past, but this one is a particular bugger. It's a 1941 Johnson 9.3 HP twin and the pistons are froze solid.

Its beeen soaking for a month now. One piston is all the way up and the other all the way down. I've pulled the exh manifold and can see the backside of the pistons and they don't look too bad. A slight ring of rust on one, but it wipesd right off. I pulled the lower unit and everything is oily and free moving.

The inside iof the carb and manifold are full pf bugs, dirt and leaves. I suspect its been outside for years. The top of the pistons and plugs are oily, so I don't think it was run without oil and has mechanical damage.

Any suggestions?

 

[Grub54891]

Sounds bad. I think the only way is a complete teardown and see what's left. I have a 15 hp, been soaking for a year. next step is teardown and see what is salavageable or not. The motor looks new, but I firmly belive it was sunk and hung on a rack.

 

[jrttoday]

I've been hearing lots of good things about PB Blaster on bolts etc. Still have some WD40, so haven't tried it.

Sooner or later, I might would try even the most ridiculous.... and the thought crosses my mind, if faced with the same. I keep some DMSO on hand for muscle sprains/strains. Mixed 65/35 with water, relieves most muscle pain in short order. Used primarily on race horses and farm animals, but the NFL, NBA, martial arts, boxing, etc etc use it all the time.

My point is this and to quote the label ---- "DMSO exhibits very extensive solvent properties. It can be used as an extraction solvent. Substances possessing a strongly polar character are generally easily dissolved in DMSO". Think I might try some next time - it's inexpensive too, $6 for a pint with 99% purity

 

[fhhuber]

Disassemble as much as possible...

That long soaking with penetrating oil, more soaking isn't going to help. Possibly the ring fused to the cylinder wall with rust due to galvanic corrosion effects.

At a certain point its either you can make it move or you will break something forcing it. The idea will be to apply the force in the manner least likely to break it or to break as little as possible.

I've had a cast iron block with stuck piston "Hot Tanked" and that dissolved the rust holding the piston in place.
The chemicals attacked the piston too, but that piston was holed so I didn't care. A good honing and the cylinder was fine. Results will vary with the corrosion involved.
I am not sure if there is a similar process that is safe for aluminum... (long time since I dealt with this type issue)
Check with a reputable local machine shop that does engine re-boring.

Brute force:

If head comes off its easier. Get it off, put a few layers of plywood down on the concrete garage floor. Set the flat , head side, of the block on the plywood. Cut wood to fit snugly down the cylinders against the back of the piston and whack that with a wood mallet.
Apply force as evenly on the piston skirt as possible... but you'll very possibly crack the pistons.
Or you can set up a hydraulic press to force the pistons to move.
If that fails you'll be drilling/chisling and breaking the pistons up to get them out.

If the head doesn't come off... you may have to purposefully weaken the pistons, break them up and take out the pieces to save the block
You can try to get a loop of wire around the pin for the connecting rod then use an automotive body puller to yank them or even adapt a gear puller...

I can't give exact instructions because of variations in blocks and not knowing that one or exactly how badly stuck it really is...

Apply just the force necessary, but apply all the force needed. the question is how to apply the force to best effect.

 

[oldboat1]

had some luck recently tipping the cylinders up and filling them with ATF. Finally freed by tapping with a wooden dowel and rubber mallet.

 

[JimS123]

PB Blaster is my goto but that hasn't worked either. There is no separate "head" - the entire block has to be separated from the crankcase and it won't budge. I've tried tapping the pistons with a wood dowel throught the spark plug holes and nothing shows any signs of movement.

Thanks for all the comments...

 

[Grub54891]

You can make an adapter from an old sparkplug, with a grease fitting. you pump the cylinder full of grease,then install the adapter,pump it up hard. everyday give it another pump or so. it'll work its way to the rust and sometimes works pretty well. only if the piston is above the ports though. Grease guns have a pretty good amount of hydraulic pressure. and safer than air pressure.

 

[kodibass]

I have a Johnson 1941 9.8 HP never got it apart the problem was that they are headless, Mine I'm sure was submerged in salt water and hung up in a shed for 20 plus years,, Mite try a propane torch thru the plug holes repeated hot cold cycling, 50-50 mix of acetone/ atf. best of luck kodi

 

[Barnacle_Bill]

For all of you that are mechanically inclined and dealing with frozen fasteners:

Penetrating Oils Compared

Machinist's Workshop magazine actually tested penetrants for break
out torque on rusted nuts. Significant results! They arranged a subjective
test of all the popular penetrants with the control being the torque
required to remove the nut from a "scientifically rusted" environment.
Penetrating oil .......... Average load
None ..................... 516 pounds
WD-40 .................... 238 pounds
PB Blaster ............... 214 pounds
Liquid Wrench ............ 127 pounds
Kano Kroil ............... 106 pounds
ATF-Acetone mix............ 53 pounds

The Automatic Transmission fluid (ATF)-Acetone mix was a "home brew" mix of 50 - 50 automatic
transmission fluid and acetone.

Note the "home brew" was better than any commercial product in this
one particular test. A local machinist group mixed up a batch and all now
use it with equally good results. Note also that "Liquid Wrench" is about as

good as "Kroil" for about 20% of the price.