Hello all, my name's Rob, and I just registered here today. I have a 1973 340 Duster that's been under a tarp for a while, and I'm just now getting to the motor.

The last date on the plates read 1980, so I'm assuming it hasn't ran since. Also, it was in a barn for 20 years, so who knows why it was put there in the first place.

Anyhow, a friend of mine recommend ATF, or brake fluid in the cylinders, so I've filled all 8 up with brake fluid.

And that's where I'm at. I really don't know what my next steps should be. If I do manage to get it un-seized do I just buy new bolt on's, fire it up, and let it burn up the dirt? Or should I look into a Master rebuild kit?

Also, what if I can get it free? After I strip it down, what do you recommend I do to get those pistons out of there safely?

Thanks for your time.  

Trans. fluid sure, brake fluid?
Anyway, the bottom line, I suspect there is rust on the cylinders and they will need machining to clean them up.
So rebuild it period.  

Well I still haven't gotten this engine to turn over. I did how ever put it up for sale or trade in, and I'm surprised at the amount of people looking for and wanting a 340 motor. I've been offered running 318's and 360's for that seized up blue hunk of junk.

What's the big deal with this motor? Is the higher revs worth that much? I believe it runs 500 more rpm, and also is a little lighter... big deal

Anyhow, would trading it in be a viable option, or would I be out of my mind to get rid of this 340 motor?

Thanks for your time guys, have a good weekend.  

Hype is worth money, and the legendary 340 came with a lot of hype, was this justified? It got the label of being the best small block period, and it was a giant killer, at least on the street.
Personally unless your restoring this in an original vehicle, then trading for a strong 360 would be a good option. Try and get a 360LA [71-91] motor, they have the better rocker assemblies, and are good for higher lifts than a later model magnum motor.  

If it's a 340 car from the factory then keep the 340 for sure!
Hell I'd keep the 340 period especially if a 4' crank comes into the picture, but I say this only cause the 340 has a larger bore size and would give you the most cubes between the 2 with the 4' stroker crank.
There are other arguments for the 340 but not worth really mentioning in this case.  

Also use a breaker bar on the crank bolt turning it clock wise to get it to turn.
Don't count on it running, like dr. said the rings have become a lil to attached to the cyl walls and when they break loose you will probably be able to see light between the 2.