Picture of Sectioned Multifuel Piston

[chigger]

 

[Kasper31]

Notice the crack, would have failed.

 

[chigger]

This one I got at a junk yard. The failure is at a weld joint. I cut it up to see the internal structure. What you can't see is there are voids in the weld. There must have been one large void or a bunch of voids together that started the crack. What I thought was cool is that there is an internal passage through the piston for oil to travel.

 

[Flyingvan911]

You evil butcher! Ha, ha. That's a good picture.

 

[JasonS]

This was from an LDS?

 

[rchalmers3]

Cool photos, thanks!

You can see the weld material is lighter than the cast metal. Are the welds a production process or was the piston repaired???

And what about the upper compression ring groves? Are they supposed to be wedge shaped or is that from all the pounding from ignition?

Rick

 

[gimpyrobb]

This was from an LDS?

No, LDS pistons have 5 rings.

 

[stb64]

Yes, it is definitely from an LDS. Remember there are 4 different LDS engines.
LDS 427-2 does not have the cooling passage and has a smaller diameter. Used in M44A1 deuces (M35A1).
LDS 465-2 has 5 rings. Used only in Ford built 8x8 trucks. Rare!
LDS 465-1 and LDS 465-1A have 4 rings. So it is from one of these 2 versions. Used in 6x6 5tons. Very common.

 

[chigger]

The piston was on a pallet in a junk yard that specializes in military surplus parts. I don't know exactly what motor it came from and I didn't know that there were different pistons. The different piston types are good to know.

 

[chigger]

The welds are production process to machine out the passage inside. I was curious about the two upper ring grooves as well. The top ring groove is actually slightly enlarged from wear, but I don’t know about the reason for the wedge shape.

 

[Nasty610]

Awesome picture Chigger. Sorry about the bashing in the other thread had a really rough day and kind of took it out on you. If you don't mind can you get some measurements on thickness of the crown? Possibly cut one of the halves in two and see if the thickness is uniform. Be great if we could machine a small amount off the top to lower the CR for some added boost.

 

[chigger]

that is why I cut this one in half. I have already CC'ed the piston and the head and measured the gasket. Now I need to measure the deck height. I created a spreadsheet that calculates the compression ratio.

 

[Nasty610]

I've always wondered why this wasn't tried a long time ago. How low do you think the CR can safely be dropped?

 

[stb64]

The first batch of LDS 465-1 engines had a 20.5:1 CR. Pistons had a slightly larger spherical combustion chamber.

 

[chigger]

And what about the upper compression ring groves? Are they supposed to be wedge shaped or is that from all the pounding from ignition?

Rick

I just did some reading. The wedge-shaped ring & groove is called Keystone. A keystone ring allows cylinder pressure to get behind the ring and forces it against the cylinder wall. It is a common design especially on the top ring. The keystone rings are less likely to form carbon deposits due to the scraping action that takes place asn the ring twists within its groove. They are also less likely to stick.

 

[162tcat]

Was there any physical damage to the piston top where that crack is? It seems like that one was destined for catastrophic failure in the very near future.