I have a seized 340 that I bought and I was wondering what is the best way of freeing the pistons. I heard of people adding Marvins Miracle Oil or transmission fluid to the cylinders, or is there something else that works better? Also one of the pistons might be rusted. Does Marvins Miracle Oil work on rust too or should I apply penetrating oil?

 

If you have rust, then use a penatrating oil. Make sure to spray it once in the morning and again in the afternoon (at least every 12 hours) for a couple of days. This will allow the oil to really penatrate the rust and make it much easier to free the pistons without scoring the cylinders walls.

Since the pistons are rusted, make sure to take a close look at the cylinder walls, you may need to bore them to get any scratches out of them.

 

thanks for the info

 

Tee,after a few days of the pen. oil. use a breaker bar andturn the crank just a little bit at a time in both directions to free up the stuck piston. If your gonna rebild the motor, then take the good pistons out to free up alot of the moving resistance.

 

Good points!

 

I just pulled my 273 apart what i had to do was soak it good with marvel mystery oil a couple days. Then I had to remove the crank and tap the pistons in a little with a 2x4 then I honed the cylinders a little till I could get the pistons out! if the walls are rusted it will more than likely need to be bored out.

 

Deisel works well also.

 

I used PB Blaster in mine. Let it soak a couple days, then added more. Let that soak a few more days, then went after freed it up with a breaker bar on the crank...back and forth as stated above. Once the piston was free, then I took a pickle fork and a brake drum and pounded it out. Block goes to the machine shop soon as I can get it there, to see if it can be saved.

Good luck!

 

thanks for all the pointers