LDS VS LDT and the real differences

[cranetruck]

FWIW.
What Continental did to improve the LDS for the 1969 M656 8x8 series trucks (rated 200 BHP at 2,800 rpm):

1) Partial load fuel control mechanism in the IP to prevent engine from putting out full power during shifting (auto trans).
2) Increased capacity oil cooler.
3) Increased inside diameter of fuel lines (from IP to injectors)
4) Injector nozzle pressure 3050 to 3150 psi.
5) Fuel filters with top loaded filter elements (love this part). Primary fuel filter is "scraper" type, good for the life of the vehicle.
6) Injectors have different orifice location, whatever that means.
7) Lower capacity oil pan with larger (magnetic) drain plugs.
Five ring pistons.
9) The crankshaft has increased counter weighting and reduced bearing clearances
10) New camshaft with improved lobe design and new timing events to decrease tappet loading and reduce danger of overspeed failure (max no load engine speed is 3,100 rpm).
11) The turbo is a "dual chambered" or "twin flow", specifically designed for the engine to provide proper air flow at all engine speeds.
12) Intake rocker arms are drilled for better lube of the valve stem.
13) The oil pump has higher capacity. Oil pressure in 5 to 10 seconds (my observation).
14) Improved exhaust and intake valves and seats.
15) Air intake filter canister with precleaner features.

There were also a number of other improvements related to running submerged.
The truck itself weighs about 3,000 lb less that the comparable M54/M809 5-ton for a higher overall weight to horsepower ratio (about 82).

 

[JasonS]

FWIW.
What Continental did to improve the LDS for the 1969 M656 8x8 series trucks (rated 200 BHP at 2,800 rpm):

1) Partial load fuel control mechanism in the IP to prevent engine from putting out full power during shifting (auto trans).
2) Increased capacity oil cooler.
3) Increased inside diameter of fuel lines (from IP to injectors)
4) Injector nozzle pressure 3050 to 3150 psi.
5) Fuel filters with top loaded filter elements (love this part). Primary fuel filter is "scraper" type, good for the life of the vehicle.
6) Injectors have different orifice location, whatever that means.
7) Lower capacity oil pan with larger (magnetic) drain plugs.
Five ring pistons.
9) The crankshaft has increased counter weighting and reduced bearing clearances
10) New camshaft with improved lobe design and new timing events to decrease tappet loading and reduce danger of overspeed failure (max no load engine speed is 3,100 rpm).
11) The turbo is a "dual chambered" or "twin flow", specifically designed for the engine to provide proper air flow at all engine speeds.
12) Intake rocker arms are drilled for better lube of the valve stem.
13) The oil pump has higher capacity. Oil pressure in 5 to 10 seconds (my observation).
14) Improved exhaust and intake valves and seats.
15) Air intake filter canister with precleaner features.

There were also a number of other improvements related to running submerged.
The truck itself weighs about 3,000 lb less that the comparable M54/M809 5-ton for a higher overall weight to horsepower ratio (about 82).

Just want to note that this is for the LDS465-2, not the more common LDS465-1 used in the 5-ton 6x6.

 

[m816]

The wrist pins on the LDS465-1 are solid. unlike the wristpins used in the deuce engine which are hollow. We ordered the proper solid wrist pin on a repair last year. Memphis said they no longet stocked the solid pin and there was no difference anyway.
They have been mixing them in their rebuilds for years and saw no failures. The parts order came through with a solid wristpin anyway.

 

[gimpyrobb]

So isn't that a LOT of weight to use the same crank?

 

[Heath_h49008]

But the pistons used in the LDS have hollow cavities for the oil channel... I would lay a wager the two offset. The problem would be if you had a "Solid" LDT piston and a solid LDS pin (heavy). An LDS piston and the LDT pin might also cause a problem (Light), but a nicer one to deal with if you shaved the crank to balance and they really did hold up just as well. Might rev a bit faster and be a bit easier on the bottom end.

I would really like to talk to one of the guys who was rebuilding these LDT/LDS engines in the 90's for Uncle Sam. I bet one oldtimer could tell us exactly what we need to know. These manuals are part numbers, but not dimensions... From what these guys are finding on the trucks, it looks like someone took 10 LDTs and 10LDSs, put all the parts in a barrel and built the engines blindfolded. There might be LDT heads without the right rockers sitting on LDS engines and vice versa. If someone can find a rocker with the part number 11641735 and one marked 40-1005152/10899107. (I'm beginning to think the 40-# is a kit, not a single rocker) we could verify or eliminate the rocker issue once and for all.

I can see why this is such a tough question...

 

[gimpyrobb]

Well, I have a set of LDT heads waiting at the machine shop for me. They are going on my LDS whenever I have some time to do the head gasket job. I can check the numbers then. I also have an LDT piston stiing here and an LDS piston sitting in the barn. Maybe I will have to dig them out and compare. The LDT DOES have a solid wrist pin though.

 

[Heath_h49008]

I'm thinking that particular LDT might have LDS pistons as well. If they put solid pins in, I'm thinking it was because they only used oiled pistons at the same time. It's the same short-block, and this wrist pin swap makes me think even more they were just putting the updated LDS components in everything at some point.

 

[JasonS]

Heath,

IMHO, your are focusing on the wrong things. The LDS's cooling channel is designed to cool the top ring land and does it at a 100F maximum! The LD, LDT, and LDS all have the piston cooling valve and oil galley in the block (at least all of the ones that I have seen). It seems like a sure bet that they all have piston cooling. Most of the piston failures that I can recall were damaged either due to a leaking injector or damaged when the rod bolts failed. The wrist pins are a ruse as well. I can't recall anybody reporting a failure of the hollow type.

You should read up on the multi's common failulre points and focus on those instead.

 

[gimpyrobb]

I'm thinking that particular LDT might have LDS pistons as well. If they put solid pins in, I'm thinking it was because they only used oiled pistons at the same time. It's the same short-block, and this wrist pin swap makes me think even more they were just putting the updated LDS components in everything at some point.

Nope, these only have 4 rings, not 5. LDT for sure. I will get pics once I have some time(next week).

 

[SCSG-G4]

This has been covered before, but the LDS-1A pistons have only three rings. The LDS-2 pistons have five rings! I have 27 LDS-1A piston and sleeve assemblies.

 

[Heath_h49008]

Heath,

....

You should read up on the multi's common failulre points and focus on those instead.

Is there a resource you could think of other than just tracking the ones users here have encountered? I'm familiar with #6 cyl block failures in seriously cranked up engines, and remember reading that someone was investigating ARP bolts to beef up the bottom ends. (I assumed that meant there was an issue.) But what other places would I look? I have access to all of the manuals listed in this thread and the FAQ/wiki... is there a "Failure Rate" listed in one of them? Like the TSB system for modern cars?

This has been covered before, but the LDS-1A pistons have only three rings. The LDS-2 pistons have five rings! I have 27 LDS-1A piston and sleeve assemblies.

You sound like a man who has been deep into these beasts! Is there a real difference? Are we chasing our tails? The rockers, turbo, IP, injectors, compression ratio/rotating assemblies, blocks, cams, timing, valves, heads and exhaust all seem to be the same or interchangeable without noticeable power increase. An oil pan and a bellhousing certainly don't give you 100lb/ft and 40hp. I love a good puzzle, but unless you have more fuel/air, or reduced pumping losses, I can't get where the power would come from.

I want to get virgin LDS465-1A and LDT465-1A side by side and just start ripping them apart to get measurements. I feel like it should be obvious, but I just don't see it...

EDIT: I'm deliberately ignoring the LDS465-2 because there are too many variables.

 

[cranetruck]

.......

EDIT: I'm deliberately ignoring the LDS465-2 because there are too many variables.

Yeah, I'm aware that my post above is not pertinent to the current discussion, but it points out some of the shortcomings of the original engine as recognized by the manufacturer at the time, like overrevving problems and they weren't looking for a lot of extra horsepower, just gained some by being able to run the engine at a higher rpm.

 

[Heath_h49008]

Yeah, I'm aware that my post above is not pertinent to the current discussion, but it points out some of the shortcomings of the original engine as recognized by the manufacturer at the time, like overrevving problems and they weren't looking for a lot of extra horsepower, just gained some by being able to run the engine at a higher rpm.

I'm quite dense sometimes... That final example of the 465 series engine would, of course, be the solution to the problems they were seeing in the earlier models.

Stronger rod bolts and a main stud girdle, lightening the rotating assembly and balancing, all the old tricks we use on gas engines, should apply here as well to increase upper end RPM survival. I guess it would depend on how many small changes you could do before it becomes cheaper for you just throw a Cummins in it and called it good. I understand it's the old saw about trying to convert a sows ear to a silk purse in metal form.

I'm also wondering if it is like the old HP ratings for gas engines...if over time the method of calculating was modified and the difference isn't what the numbers seem to indicate. But anyone who rebuilds both types of engines should know what it takes to get each to the specified outputs when given the list of interchangeable parts... That data MUST exist.

 

[gimpyrobb]

To add to the mix, there are newer LDS pistons with lower compression ratios. You can tell by the black coating on top.

 

[Heath_h49008]

I thought they were all 22:1, but there was a small difference in the design of the "Cup" for turbulence creation, and a coating.

I'm just trying to isolate the 100ft/lbs, 40hp from LDT-1A to LDS-1A because it is the smallest change for the greatest improvement. I don't think the deuce is really a safe bet for high speeds or high HP (Brakes being the first issue...) But that 100ft/lbs sure would make it safer in traffic and might keep us from taxing the engine so heavily when we do need power.

I know this tread has a broader scope, but I'm working on that one little part first. (And kind of ashamed I can't get it yet) More reading after I get my classwork done. At least I have a fun subject to learn.

 

[Heath_h49008]

I'm bumping this in case it catches the eye of someone who has rebuilt both engines and knows the answer.

Also, my M35A2 LDT should be coming home in a short while... I will pick this up when I have one in my hands.

 

[islandguydon]

I have a questtion, which is better for HP, sound and over all performance...?BTW I like quiet..

A C-turbo or a D-turbo............?

 

[fuzzytoaster]

I have a questtion, which is better for HP, sound and over all performance...?BTW I like quiet..

A C-turbo or a D-turbo............?

I don't remember specifics numbers on the turbos but the D pushes slightly more air. That being said the performance gained is negligible at best and boils down to do you like the whistle or not. Please correct me if I am wrong anyone.

Turbo:
C - Whistle
D - Not Whistle

 

[73m819]

The Ds main job was to cut down on SMOKE

 

[Loco_Hosa]

So, the injection pump starts pumping fuel sooner on the LDS than the LDT, which brings down EGTs, is this a fact, or am I too tired and stupid to fallow this thread?

Bringing down the EGT, means you can turn up the fuel more, accounting for some of the added power in the LDS, correct?

Before my father began to turn up the fuel on his 90s Ram, he took the IP to be "Fiddled" with, and they adjusted when it pushed fuel, and they "Balanced" it. Perhaps I need to contact them and ask if they can do the same on the LDT engine my truck has, or if they can only do this on Cummins for whatever reason.....

I dont remember it being abhorrently expensive, is the IP on 12 valve cummins worlds different than our MF engines?

This HAS to be a stupid question, if it was that simple then everyone would already have done it. Please, aim your flame cannon here and FIRE AT WILL!

I have a questtion, which is better for HP, sound and over all performance...?BTW I like quiet..

A C-turbo or a D-turbo............?

The less high pitched D turbo is less damaging to your ears (Logic dictates)

I happen to love the way my D turbo sounds, which is good, and may have something to do with telling myself over and over that I didnt need a C turbo....

Lastly, I have read that the C turbo is more prone to problems when not cooled correctly. (Not to say that you dont need to cool your D!)