Pulled the head on my WD

I think I have a pretty good idea where the compression went on #4. The cylinder sleeve looks good yet, but the head and #4 piston took a pretty good beating. I have an extra rod to use, as I would think the original might not be trustworthy any more after absorbing such a shock, but I don't have an extra oversize piston to use. I am hoping to fix this up inexpensively-not because I have to, just because it is a challenge.

Head is likely ok but magnaflux would be smart.I'd replace the other valve too.all the pounding might have lowered it 's integrity .

my theory is it was started with a sticking valve, and the piston and exhaust valve were introduced in a rough manner. I am no expert, but it seems to me that could weaken the stem and also get it started flexing each time it closed. Probably could only flex about "x" number of times 'til the head popped off. The valve head was discovered in the bottom of the oil pan along with some aluminum chunks. That to have been a horrible racket when it let go.

Edited by redline - 12 Jan 2011 at 9:03am

Hmmm... yeah, that's some interesting heiroglyphics that the valve fragments left in the top of that piston.  Good thing it was a dished piston to begin with... otherwise, it'd probably be a whole lot worse.

Check the sleeve really good, just in case that valve wedged in there enough to swell out the piston and open a slight crack in the sleeve.

From a low-budget repair challenge perspective, think I'd check the mains closely, look for bent rods on the other three cylinders, and of course the crank... but don't think it'd be necessary to yank the engine or crank...   if the rod's okay, I'd say stick a used piston and sleeve in, scrub the head, inspect, mebbie magnaflux it, put in a used valve, lap it, a different spring, reassemble and fire it up... and listen for odd noises (which is always a challenge in old engines).  I'll bet that old girl will go back to business as usual.

I popped the head off a sodium filled valve in a VW once. It locked up the engine with the head of the valve on edge in a new slot it the top of the piston. It was an aluminum head too, so I replaced head, valves, pistons and cylinders, ended up with a bigger bore kit. I think what did it was that on a previous valve job, I'd replaced the original aluminum bronze valve guides with steel to get a longer wear life, but the steel didn't stay in good contact with the aluminum head when it expanded and so the valve overheated. I wan't pushing it hard when it broke, but there was a brrrrp and no more engine power. Probably just a few revolutions.

Having free sodium metal running around makes taking that engine part rather interesting as bits of metal ignite from moisture or the heat of the torch expanding the piston to get the piston pin out.

Gerald J.

Mitch, I think you left the r out of free.

Guys, some of you are seeing an optical illusion. The piston is not dished and does not have an offset circle on top. It's the piston at the bottom of the cylinder with the shiny walls giving you the illusion. Just had to point that out otherwise all good advise.