acquired a 71 340 engine that has sat in a old barn floor for 40 years. dragged it home and now before I try to turn it over I'm wondering what steps to take. I can see one
exhaust valve is open and some rust. Any suggestions as to what I should put in the cylinders ie.. engine oil, diesel fuel etc... Going to remove spark plugs and try to look
inside with a scope. Take the valve covers off and back off the rocker shafts??? Anyway just looking for any suggestions and thanks to all.

Bennoel

Why not just pull the heads off?

Just put a breaker bar on the crank bolt and see if it turns. no big deal, if it does it does. If it does not then you will go to step 2 ....find out why. what are your plans for this engine? Do you have any? don't over think it. If it turns good. if it doesn't. well see step 2. Was the barn dry? do you have history on the engine? you wont hurt anything by just trying to turn it the way it is. Report back

Sitting in that kind of environment ,. At the very minimum I would pull the heads and oil pan to take a look.
I opened up a 440 that had been sitting in the car for about 15 years and found all kinds of surface rust in the bores. It was inside a dry garage with concrete floors . Never tried to turn it over, owner said pull it and go thru it.

It's not like it's going to be a runner

More likely have mechanical welding of rings to walls.
Pull heads, rap the top of pistons with a large rubber/wooden mallet.
Spray everything with liquidwrench (or equiv), let set awhile
Then attempt to turn via damper

A friend of mine got a free 283 Chevrolet for a T-bucket project he was working on. It had been outside for years and was locked up solid. We filled the cylinders with diesel fuel and let it sit for an hour or so. Then we rocked around on the breaker bar and pry bar on the flex plate and it broke loose. Put some fresh oil in it and fired it on the test stand. It smoked like crazy for a few minutes then quit and ran nicely. He changed the cam and heads and beat that thing like a rented mule in that t-bucket for several thousand miles before he sold it.

Not saying this is a good idea but I would try and make it run, but I think that kind of challenge is fun.

40 years? That 340 is most likely not going to turn over. Even if it did there will be valves stuck open and the pistons will hit them. Plan on a full rebuild. Pull the heads, soak the pistons with Kroil, let set for a couple days, soak again and maybe they'll come loose.

did the same to a 392 in a 58 imperial, only we used ATF.
boy did that baby smoke !

I haven't heard that in a very long time. My Dad used to say it.



Tim

I saw an episode of Chasing Classic cars and the old guy "Roger" used Marvels Mystery oil on an engine / vehicle that had been sitting for many years. They removed the spark plugs and used MMO in the cylinders. After allowing it to soak for a few days, they placed the vehicle in gear and gently rocked the car, finally freeing up the engine. I enjoy when they show crusty old Roger and his tricks of the trade. The guy has been around a long time and appears to have knowledge about all kinds of vehicles. Perhaps investigate using MMO if you don't take off the heads etc. per other suggestions.

Always thought Marvels Mystery Oil was just ATF. Did they use to put a quarter in the can as a sale incentive (gas station)? I think a total rebuild is in order.

If they did, it would be a silver quarter. It would be worth about $3.15 on todays junk silver market.

34 years sitting...I used wd40 in the cylinders, sprayed it in with the straw and tried to spread it all around in the cylinders.I sprayed once or twice a week for months..just letting it sit and soak...then spun it with a flywheel Turner and it broke free..sprayed more wd40 and rotated the engine some more..then new plugs, fresh gas from a can into the fuel pump then...
https://youtu.be/OSkDnAzu9w8

When I was 17 or 18, I got a 239 Ford that had been sitting out in a guy's backyard with a tin can over the carburetor for heaven knows how many years.

Fresh plugs, fresh points, kit in the carb. Ran like a Swiss watch.

I suspect this was only because of my ignorance - had I known better, it probably wouldn't have ran at all...

Fast forward 3 decades. Bought a 2002 Sportster engine with 3000 miles on it; pulled from a wrecked bike. went to put cams in it, check the crank run out while the cam chest was open and found almost .006" TIR on the pinion shaft. Tearing the motor apart so I could split the cases and true the crank, found one of the cylinders had got condensation in it.

Basically, if I had tried to run that motor as it was, I wouldn't have got much life out of it.

Like previous postershave pointed out, a gasket set is not terribly expensive. If the motor gets torn down, and everything is just fine, then it goes together with nothing more than the gasket kit.

If there's issues, probably not going to get any cheaper to fix by running it

Even if it turns, what is the point of not taking it apart. You said you already see rust in the bore. This will not have a good hone, valve job, valve stems or ring tension.

Take it apart and rebuild it properly.

Any time I work on an eng.that has sat for awhile I put a couple of OZs of ATF in each cyl. & then use compressed air with a hose/pipe going into the cyl. to blow the ATF around the cyl. so I know the entire cyl.has gotten lubed,let it set for awhile & then see what happens,Ill also lube the valve train well & if possible spin up the oil pump to lube the bearings,or if the eng.frees up Ill crank it around w/o plugs to pump up the oiling syst.