LDT-465-1C vs LDS-465 Multifuels

[tm america]

i'm sure one of my pistons will make it,s way out of the side of the engine soon if i keep the fuel turned up and the pedal to the floor

 

[SCSG-G4]

Gimp,
I just looked at the pics from the piston auctions. One out of the sleeve appears to have just three rings. I'll check when I get home, as I would up with one that was removed from the sleeve - probably for the pictures.

 

[EveOfDestructionDeuce]

Thanks for informations, but I have not yet a really good answer for sure..... @gimpyrobb please could you measure the sleeve from the LDS, inside/outside & lenght.May be you could measure piston high/lenght w/o push it out. Compression volume (bowl cc) and stroke will be the same on both engine types?Are you sure they are using a different amount of rings?

 

[EveOfDestructionDeuce]

I`ve got an old ldt-465-1C piston/sleeve here so I could also measure them. It have 3 rings on them.....

 

[cranetruck]

Matt, from the TMs, the bore is the same for all models, 4.56 inches.
The LDS465-2 model has 5 rings vs 4 for the others.

Edit: Added images.

 

[stumps]

So what did they do to the LDS to make it put out 210HP vs the LDT's 140?

-Chuck

 

[cranetruck]

So what did they do to the LDS to make it put out 210HP vs the LDT's 140?

-Chuck

It's actually 195-205 hp at 2,800 rpm.
Crankshaft: "Increased counter weighting and reduced bearing clearances"
Camshaft: "Improved lobe design and different timing events to reduce tappet loading and reduce over speed failure."
Turbocharger: "Dual chambered, designed specifically for this engine to provide proper air flow at all engine speeds."
Oil cooler: "Increased capacity"
Oil pump: "Increased capacity"
Intake valve rocker arms: "Drilled passage for better lubrication of valve stem."
Exhaust valves and seats: "Improved."

I'm quoting the manual, so I can't help you much beyond that. The -2 engine was only used for the m656/xm757/xm791 8x8 trucks (less than 500 delivered to the Army, all in 1969)

 

[emr]

This was/is a great thread...

 

[stumps]

It's actually 195-205 hp at 2,800 rpm.
Crankshaft: "Increased counter weighting and reduced bearing clearances"
Camshaft: "Improved lobe design and different timing events to reduce tappet loading and reduce over speed failure."
Turbocharger: "Dual chambered, designed specifically for this engine to provide proper air flow at all engine speeds."
Oil cooler: "Increased capacity"
Oil pump: "Increased capacity"
Intake valve rocker arms: "Drilled passage for better lubrication of valve stem."
Exhaust valves and seats: "Improved."

I'm quoting the manual, so I can't help you much beyond that. The -2 engine was only used for the m656/xm757/xm791 8x8 trucks (less than 500 delivered to the Army, all in 1969)

That's interesting!

Two of the changes relate clearly to the higher speed operation: the increased counterweight, and the improved cam lobe design. It would appear that they were worried about valve float, or tappets launching themselves off of the cam, and felt that increasing the spring tension would prematurely eat the cam. Increasing the counterweight would reduce the vibration due to the piston weight, but it would increase the side to side vibration due to the heavier counter weights. The counter weight change might have been to correct an original omission when they went from the lighter diesel pistons to the heavier MF pistons.

The only change that could likely relate to rod failures is the increased oil pump capacity. It could be that oil wasn't getting out to a particular rod in sufficient quantity, causing rod bearing failure, and subsequent crankcase penetration.

I got the 210HP figure from the vehicle specifications in the Resources section of this site. The manuals seem to flip-flop between quoting gross and net HP values for the engines. Accessory load seems to be about 10HP.

-Chuck

 

[EveOfDestructionDeuce]

Thank you very much! I understand that the piston/sleeve sizes are the same, except one more compression ring for the LDS.....

The question will be what happens if I use two new LDS pistions with 5 rings in my LDT engine ?(4others are the used originals with 3 rings). They are better and saver, and provide not so many compression loss, because of one more ring.Normally it should be no problem, otherwise this is a rought/raw engine and no well balanced race engine....

 

[stumps]

Thank you very much! I understand that the piston/sleeve sizes are the same, except one more compression ring for the LDS.....

The question will be what happens if I use two new LDS pistions with 5 rings in my LDT engine ?(4others are the used originals with 3 rings). They are better and saver, and provide not so many compression loss, because of one more ring.Normally it should be no problem, otherwise this is a rought/raw engine and no well balanced race engine....

I think I would try really hard to keep the set of 6 all the same. Surely there must be some 3 ring pistons somewhere that you could use? It isn't like there is any shortage of LDT's with holes in their crankcase

-Chuck

 

[SCSG-G4]

I now have the piston in my hand. It does have but three rings, all near the top. Looks most like the first diagram in page three , with only one ring for #1 and #2, and four small holes drilled from inside the head to the bottom of the oil ring. Ord Dwg is E6799-G, and the number stamped inside the piston is 19P04 12380090