Help with rebuild

[72jimmycst]

I've just torn down a 400 that had been sitting around for a few years. The head gasket was trashed and leaked into a couple of cylinders one of which is now stuck. I have got the crank out. Any body know the best way to free it up?

 

[Kiwi John]

Let some penetrating oil soak around the top of the piston for a day or so, then put a block of wood on top of piston and knock down the bore gently with a hammer. extract piston and rod thru crankcase.
You'll probably have to hone cylinders or bore the block oversize anyway.
Good luck with rebuild.

 

[72jimmycst]

Thanks

Kinda what I thought but not sure if the piston on a 400 will come out the crankcase.

 

[Mad-Dog]

Now I've heard it all.......

then put a block of wood on top of piston and knock down the bore gently with a hammer. extract piston and rod thru crankcase.

I like the idea of soaking it with penetrating oil but I would not attempt to remove the piston thru the crankcase
The piston comes out the same way it went in, from the top

 

[Guss]

PB Blaster will probbably work the best

 

[Kiwi John]

Oh, OK. Hold on 72jimmycst.

Mad Dog: I would have thought that since the crank is out he could knock it thru from the top.?

Sure, bang it up from the bottom but sometimes the rings can catch on the 'lip' at the top of the bore and damage the ring grooves in the pistons. And you have to hold the conrod steady when you hit it.
General principle anyway. I was taught to bring them out topside if they are nice & slidey, sure. But when jammed, siezed or, as here, rusted, get'em out the easy way. I'm not familier with this engine block. Is there a physical reason they wont knock thru from top?

 

[HarryH3]

Is there a physical reason they wont knock thru from top?

The main bearing castings intrude into the area where the piston would come out. It has to go out through the top. However, pushing it down a bit and cleaning up the cylinder wall a bit before pushing the piston out the top isn't a bad idea.

 

[72jimmycst]

Yeah it's too bad, the rest of the pistons are in great shape, I think the lower half only had about a thousand miles on it. The only other prob was one lobe on the cam was completely rounded off. Just my luck one cylinder, just one lobe= nearly complete rebuild. Now if I can just find one bad valve in the heads my girlfriend will be soooo happy!