freeing stuck pistons due to rust

Pete. (l33t FS) said:

In reply to kb58 :

What usually seizes the engine is not just the rings rusting to the bores, but also the rings rusting to the pistons and a rust clog on the bores themselves keeping things from moving.

There will be bore damage.  Not ideal but usually not enough to prevent compression.

I have seen a couple times the pistons damaged from the rust on the rings expanding and crushing the ring grooves, leading to excess ring side clearance, which causes flutter and poor sealing.  Again, not the end of the world from a dirt floor and sandals "make the engine run" perspective, not great from a performance perspective.

 

But yeah, working quickly means working quickly   I definitely would not use acid as a first resort.

It wasn't that uncommon back in the 1950's to free up frozen pistons in old Ford  flatheads  with whatever magic elixir  and then get the engine running  with smoke billowing out from breathers and tail pipes etc.  

  Drive it hard until it got too hot. Let it cool back down and repeat. 
   Eventually  only a slight blue haze  followed the truck and oil consumption  was acceptable. 

Racebrick said:

I tried mmo on one bank of cylinders. Since the heads are off, I am working one side at a time.  Two cylinders had emptied, so I took that as a good sign since the liquid is getting past the rings. I am now letting a 50/50 mix of acetone/atf sit in the other bank. After a day or so I'll give it a wiggle, and if it doesn't move I plan to switch to vinegar for a couple days and see what happens.

And 24 hours later, what is the verdict?  

Apexcarver said:

What about just soaking with evaporust? Not as hazardous to other materials.

Was just going to suggest that, perhaps with an IV drip or aquarium pump to keep it flowing/circulating.  

This is of interest to me because I have a RD400 engine that is massively rusty in the bores.  The problem is the pistons are only covering half the exhaust ports so any liquid poured into the bore will simply run out the exhaust port.  

Ideas?

I convinced the Pistons to come out. It was really only two that were holding them in there.

1.

2.

stroker said:

This is of interest to me because I have a RD400 engine that is massively rusty in the bores.  The problem is the pistons are only covering half the exhaust ports so any liquid pored into the bore will simply run our the exhaust port.  

Ideas?

Can you tilt it at the proper angle for that not to be a problem?

stroker said:

This is of interest to me because I have a RD400 engine that is massively rusty in the bores.  The problem is the pistons are only covering half the exhaust ports so any liquid pored into the bore will simply run our the exhaust port.  

Ideas?

Trace a template of the exhaust onto a piece of paper and cut out a flat blank to hold it in out of either sheet metal or maybe coated plywood. I'd also add a bead of some silicone sealant to keep it from seeping out. Then fill.