LDS VS LDT and the real differences

[patracy]

All fuels have a Stoichiometry ratio so you are flat wrong.

That is very much correct. However diesel engines lack a butterfly throttle, so stoichiometric fuel mixture is never sustained during normal operation. Compression ignited engines swing from rich burn to lean burn without issue. The burn condition is determined by engine load and fueling. It isn't like a gasoline engine where the incoming air is mixed with the fuel before entering the cylinders.

 

[Loco_Hosa]

Whats that have to do with the differences of an LDT or an LDS?

Let me get my **** and

Ok, this thread is about finding the differences between an LDT and an LDS, correct. However, it has shifted more in the direction of finding out what the RELEVANT differences are. Why does one make more power than the other? What would have to be changed to on one to get the results of the other.

If you just want a list of part numbers that are different, get out your TM and your highlighter. Not. That. Hard. If you would like to know what parts of an LDS cause the increase in power, then stick with us while we try to figure that out.

I brought up the idea of the smart phone accelerometer because it would give us a way to test changes such as, swapping an injection pump from an LDS to an LDT engine. I dont think the "Butt Dyno" is sufficient enough to determine if this is the deciding factor.

Some differences have been found in the TMs, but we have then found that they are NOT accurate. The rocker arms, the injectors, and a few other pieces that were supposed to be found on the LDS have been found IDENTICAL on the LDT. LDT engines found with the two whole injectors, LDTs and LDSs found with identical rocker arms, ect.

LDS engines have also been seen with C or D turbos, but still (Reportedly) out performed the LDT. This to me indicates that it was NOT the "Deciding factor" for all this power.

The only thing everyone can agree on is that the LDS has oil squirted at the underside of the pistons, and an extra piston ring. This would reportedly reduce EGTs by 100 degrees or so. (Allowing the fuel to be turned up a bit, but has been decided doesnt make "The difference").

The injection pump between them is DEFINITELY different, which has the potential to make a LARGE difference.

None of the facts in this post are my own, they are all things I read in this forum. If you are so unsatisfied with this thread, then you are welcome to contact a mod and politely inform them that you feel this thread has run its course, and needs to be shut down.

 

[patracy]

Sorry, but I can't agree with you on your "everyone can agree" on statement. In my hands on experience, I removed pistons from an LDT engine with FOUR rings. I used a LDS piston liner kit (NOS), those pistons had three rings. The LDT engine had oil squirters as well. Although, the liner kit included new nozzles. The new nozzles have two ports instead of the single ports the LDT had to start with. That's just what I know first hand, stuff that I've had my hands on and seen with my own eyes. Instead of "I heard from so and so, who knew someone, that worked with someone that repaired these engines".

However, I will agree that I don't bear much credit to the turbos on ANY of these engines. They're all undersized, old as the hills in design, and weren't really added for massive power gains to start with.

 

[Loco_Hosa]

Sorry, but I can't agree with you on your "everyone can agree" on statement. In my hands on experience, I removed pistons from an LDT engine with FOUR rings. I used a LDS piston liner kit (NOS), those pistons had three rings. The LDT engine had oil squirters as well. Although, the liner kit included new nozzles. The new nozzles have two ports instead of the single ports the LDT had to start with. That's just what I know first hand, stuff that I've had my hands on and seen with my own eyes. Instead of "I heard from so and so, who knew someone, that worked with someone that repaired these engines".

However, I will agree that I don't bear much credit to the turbos on ANY of these engines. They're all undersized, old as the hills in design, and weren't really added for massive power gains to start with.

Your first point makes me give up on LDS vs LDT and I am tempted to just unsubscribe from this thread. Im ready to assume that all our engines are a mix of the LDS and the LDT designs.

Their are many other experts on the forum that say our turbos are overkill for our engines. Either way, that's off topic to this thread.

All in all? I have learned a lot from this thread. End result? Im just going to buy a pyro and boost gauge, crank it up, and you can call my engine whatever the **** you want.

 

[patracy]

I'm not picking a fight, I'm just trying to add fact about the piston/squirter debate. I just know what I have in my hands. I totally agree with you though on these engines being a hodge podge of LDS and LDT parts.

I'll also be with you on the last statement of "install a pyro and boost gauge, crank it up, and call it the big goofy sorta diesel engine that makes these trucks great".

 

[rwelker]

Wow! What a thread! Twenty five pages to read through. My experiences: (all M35-A2's)1st truck with LDT-465-1C. No smoke. Great fuel mileage. Alot of noise. Slow as a rock. 2nd truck Ld-465 non turbo. A lot of smoke, no power, so-so fuel milage, pretty quiet. (had a muffler). 3rd truck: LDT-465-1D. Not a bad runner, some smoke, decent power, decent fuel mileage. Dropped a bearing. 3rd truck: LDS-465-1A. Runs like a raped ape. Lots of smoke. Likes fuel. I would never go back to anything else. Just my two cents.

 

[JasonS]

The only thing everyone can agree on is that the LDS has oil squirted at the underside of the pistons, and an extra piston ring. This would reportedly reduce EGTs by 100 degrees or so. (Allowing the fuel to be turned up a bit, but has been decided doesnt make "The difference").

.

The second oil squirter does not reduce EGT by 100F.


Right from Continental's literature:

"Oil is circuiated through the annulus to reduce the temperature of the ring groove and thereby eliminate the requirement for high additive oil..." "This piston cooloing development has resulted in an approximate 100F reduction in top piston ring groove operating temperature."

My take is that if you use good, modern oil (the above was written in 1964) this difference is superfluous.

 

[Heath_h49008]

I have fuel leaking out of the 12 point plug on the side of my HH. It is an LDS motor. I am getting ready to swap in a 100a head. I will let you know of any noticeable differences.

Anyone know what causes the head to leak at that plug?

Necrothreading...

Hey Gimp, did that head make any difference?

I happen to have that LDS465 1C pump but the number on the Ambac tag doesn't seem to match either the 101 or the 100 part number.

Just curious.

 

[gimpyrobb]

I'm not sure when I posted that, but I ended up swapping a plug from another head and it stopped the leak. I do know that this is a seemingly common issue that others have had happen. The plugs get cracks in them. It took me 5 different plugs to find one that fit well(its a lapped fit).

Did that help any?

 

[sandcobra164]

A little late but very interesting book katahdin!!! My truck never weeped oil from the front head until I pushed her hard by towing some 5 tons. Perhaps the Multi us just not suited for towing heavier loads. It seems to have subsided for now as it only tows a M105.

 

[Bigred77]

Im currently in the process of putting a lds pump on my ldt. and noticed the different timing marks on the front balancer. The ldt timing mark is actually further advanced than the lds. whats up with the different tdc locations if the bottom end is basically the same?

 

[tuff-truck-guy]

wow i have read through 25 pages n am almost more confuzed than when i started"thnx dh for trying to keep thread on track" as from what i have "understood" lds makes more hp/torq from more air / fuel? has anyone checked the intake plenum and exaust size? more air / fuel=more power right? mabe its not just a 1 thing deal that makes the engines different ok ie the intake rocker may be a touch bigger. pump may put a little more out but as i read earlier the air filters tm was also different . lds has larger cfm's than ldt. parts are interchangeable, are the intake and exaust the same as well? i dont really know but that would make sence 2 me. normally if someone hops up a engine, 1st thing is a intake and exaust mod then fuel and so on right?

 

[Heath_h49008]

From all available data, the engines are functionally identical except for the pump/head, timing of that head, the extra cooling in the LDS pistons, and the bigger turbos on some LDS to deal with the increased fuel/power.

The LDS/LDT are the same engine in different tune and with different accessories to deal with the increased fuel/power/heat.

Tubos do not increase power per se. They allow the engine to remain cool while the extra fuel that makes the increased power is burned. Any change in timing would also effect the burn time and heat produced.

The reason it seems so hard to find the difference is, there really isn't one more complicated than more fuel and more cooling.

 

[m-35tom]

different cam, pistons, fuel rate, rocker arms maybe, turbo flow, etc. in reality i have had both and cannot tell the difference between them if the LDT is turned up to the same boost as the LDS. it was never meant to be a high output engine, and it was never meant to turn more than about 2200 rpm.

 

[gimpyrobb]

different cam, pistons, fuel rate, rocker arms maybe, turbo flow, etc. in reality i have had both and cannot tell the difference between them if the LDT is turned up to the same boost as the LDS. it was never meant to be a high output engine, and it was never meant to turn more than about 2200 rpm.

I agree with everything except, the RPM. I thought the LDS was governed at 2900rpm? I don't run mine over 2500, but thats just what I do.

 

[Flyingvan911]

I keep my LDS at or below 2,500 also. I would like to see a modern scientific test and analysis of the engine and parts at 2,200 rpm vs 2,500.

 

[Heath_h49008]

I would just like trustworthy rod bolts and a balanced rotating assembly.

Mine is tight, low time and not a rebuild... so it's a little lower on my priority list.

Oh yeah... I have the LDS pump as well, so it's a crapshoot what my power is right now.

 

[Heath_h49008]

Camshaft Fed. stock #2815 808 6978.

Same cam. As per post #36

 

[gimpyrobb]

Camshaft Fed. stock #2815 808 6978.

Same cam. As per post #36

I understand they are listed as the same, but if you were to hear an LDS next to an LDT, they sound different, like one has a "hot" cam. I can't imagine what would account for that sound other than a cam.

 

[doghead]

intake rockerarms(ratio). It's like having a "hot cam".