LMM: LMM with 222,000 tear down rebuild

[THEFERMANATOR]

The 4500/5500 kodiaks had larger trans coolers, larger radiators, lower temp larger fan clutches, I believe a larger diameter fan blade, different engine mounts(don't know if this was for packaging or block rigidity), different trans bolt pattern, used the ALLISON not GM style extension housing, different air box, were detuned, as well as quite a few other differences. Even the last kodiaks were only rated at what 310 hp at the flywheel, so that would be around 250 or so at the wheels, not 400. MD trucks go for slow and steady wins the race.

Maybe it's time to look into one of the new BANKS engines he's building for the military. I believe he said they redesigned them to run in the 500-600 Hp range without any emissions controls. Seen he had posted up pics on FB the other day of hos 1st castings on there way to GM for final machining before he assembles them. I want to say he was shooting for 700-800 HP for the marine versions.

 

[hondarider552]

That weight rating has exactly nothing to do with the engine though.

True, but that wasn't what I was getting at.

 

[malibu795]

Some 95k on pistons, some 70k of that this block/rings
Bore was set at 4.095, which is spec for new pistons.. in whichi put used pistons which pretty much loosened the ptwc.
Here is couple vids of #1 and #2 pistons
https://youtu.be/dz0GBzGmkxc
https://youtu.be/Di-eGSBpBWs

Protrusion is .006-.008"
Time for some sleep

 

[PureHybrid]

What's the actual ptw clearance now? What do the piston skirts look like?

 

[TheBac]

As in NOT 90° from the pins, more like 10:30, 1:30, 4:30 or 7:30, if the arrow on the pistons was 12 o'clock. During the power stroke you don't want the thrust load of the piston (think piston skirt area) to push on the ring gaps. But you don't want the gaps over the pins either, or they'll twist.

Sorry to be late to the discussion, but I was just reading all this. Did you know that there is no literature available to the public that describes the proper orientation of the rings on a Dmax piston? I mean, nothing.
I ended up placing all four gaps in an "X" pattern on mine, 45* out, with nothing over thrust or pin. No excessive oil consumption noticed since install 6-ish years ago. Would be interesting to dyno the truck and see where power is, though.


Good luck Adam.

 

[malibu795]

What's the actual ptw clearance now? What do the piston skirts look like?

No rhyme reason here is #8.. top ring is very loose moving inline woth piston travel.. 2nd ring is sticky/ feels gummy
Top ring was at 130 o'clock to thrist 2nd was at 6 oclock

 

[malibu795]

Sorry to be late to the discussion, but I was just reading all this. Did you know that there is no literature available to the public that describes the proper orientation of the rings on a Dmax piston? I mean, nothing.
I ended up placing all four gaps in an "X" pattern on mine, 45* out, with nothing over thrust or pin. No excessive oil consumption noticed since install 6-ish years ago. Would be interesting to dyno the truck and see where power is, though.


Good luck Adam.

No worries.

Thanks for info

 

[Fingers]

That skirt wear is about normal for 100 Kmi. They can be recoated.

The ring in the top picture looks like it has a burn through. The shine should be consistent all the way around. The inter-ring build up indicates top ring blow by. There is always some, but that looks heavy to me.

From what could see of the tops of the pistons, they don't look to shabby. Get them ultra sonically cleaned. DO NOT wire brush them.


Check your bores. I think you will find them tapered.

 

[PureHybrid]

I think the skirt looks like hell, even if it is only the coating. I will agree on the top ring, but I doubt he'll find a tapered bore. Maybe reduce your timing (as suggested earlier, but I'm not a tuner) to let more heat into the exhaust instead of the piston taking it all. What do the upper rod bearings look like?

Did you happen to mic the cylinders and pistons before assembly?

 

[Fingers]

Quick review. ~100,000 miles on pistons. Hard pulling almost continuous service. Really should be going by engine hours not miles.

Coating is only 2 mil thick and is still visible in the picture. Not bad for the service. Show me similar service pistons that look better. If the top ring lands and pin bores are still in good shape, you can probably re-coat, and re-ring. Though I personally would check them over completely.

It is all about cylinder pressure. If you want a long lived engine. Pay up front to tune using cylinder pressure while making good power. Seat of the pants will NOT make it.

The pistons can handle the higher pressures just fine. It is the other parts that suffer long term like the rings, crank, and bearing.

BUT this is not my engine, build, or endeavor. So my opinions are just that, opinions.

Speaking of opinions, I always stagger my ring gaps by 120° with none aligned with or perpendicular to the pin.

 

[malibu795]

Fleeces engine shop did the measurements/machine work..
i have mic and bore gauge on order as i can't get ahold of anyone local to me to borrow.
I have no clue who does ultrasonic cleaning local to me.
I do have access to a substantially large pressure washer with heat, talking ~4000psi @200° water temp at 4gpm

Haven't taken any steel wire brush to them. Nor do i pkanon it.
Top ring isn't brunt through. Or discoloured

Cylinder walls do look slightly tapped... Less than the OEM blocks i pulled apart though. i can see rings about 1-1.5" do from tdc..camera cant pick it up though


So much for being quick ring job.

As for less timing... Ive tired that.. mpg, grade speed and HP all drop and EGTs go up and truck starts to haze under throttle

 

[malibu795]

Quick review. ~100,000 miles on pistons. Hard pulling almost continuous service. Really should be going by engine hours not miles.

Coating is only 2 mil thick and is still visible in the picture. Not bad for the service. Show me similar service pistons that look better. If the top ring lands and pin bores are still in good shape, you can probably re-coat, and re-ring. Though I personally would check them over completely.

It is all about cylinder pressure. If you want a long lived engine. Pay up front to tune using cylinder pressure while making good power. Seat of the pants will NOT make it.

The pistons can handle the higher pressures just fine. It is the other parts that suffer long term like the rings, crank, and bearing.

BUT this is not my engine, build, or endeavor. So my opinions are just that, opinions.

Speaking of opinions, I always stagger my ring gaps by 120° with none aligned with or perpendicular to the pin.

Ive been wanting to get on marks dyno with his pressure sensor. Time and money been lacking
Seat of pants is rather pointless for how heavy i am.. usually make a change then check mpg, grade speed, and egts avg with untouched fuel settings
Timing is power/efficiency but too much kills parts

I still have the OEM pistons that failed with ~222k in them these look better

100k miles plus idle time, figured some 22-2500 hours on them. Idle time being the main variable... i avg 58-60mph during the week, with ~2000 miles a week...Never tracked engine run time..

Why set ring gaps at ~120° vs ~180° to each other? Assuming i read that statement right.
Plan is to set ring gaps at ~180° to each other and ~45° to wrist pin

 

[malibu795]

On topic of piston skirt coating compared yo the OEM LMM i killed that started this thread. Running extremely similar tuning..
New fingers vs 222k LMM OEM piston

Looking at old bearing pictures the clevites look substantially better than this.
OEM@222k

Ill get the upper rod bearing pic posted out of brake cleaner

 

[jlawles2]

At first glance the top ring looks burnt. However It appears that there is oil on it.

Did you pull one of the top rings off and put it back in the bore, then check the end gap? The edge of those rings looks like its flat. When I pull the pistons on my stock engine to replace a bent rod, the top ring was "domed" with a slight flat spot in the middle where the ring had wear.

Looked in my Haynes manual (10331) and it says to put the rings as follows based on 9:00 being front of engine:
Top compression ring 10:30
Oil expander ring 1:30
Second compression ring 4:30
Oil ring 7:30

Top compression ring should be toward front of engine on both sided.

Standard engine specs:
Piston ring end gaps are listed as:
Compression ring
Standard 0.3-0.45mm
Service Limit 1.37mm

2nd ring
Standard 0.50 - 0.65mm
Service limit 1.35mm

Oil Ring
Standard 0.15 - 0.37mm
Service limit 1.2mm

Ring groove clearance:
Compression ring
Standard 0.15 - 0.17mm
Service limit 0.26mm

2nd Ring
Stancard 0.01 to 0.03mm
Service limit 0.10mm

Oil Ring
Standard 0.01 - 0.03mm
Service limit 0.12mm

Piston bore clearance 0.090 - 0.120mm

I know you probably have already checked everything. From reading your post, it looks like you double check everything 2-3 times.

 

[Fingers]

And the compression difference between the LMM and Ovals?

 

[malibu795]

And the compression difference between the LMM and Ovals?

LMM 16.8 to 17.5 with ovals
Had to add 1-2° of timing to the ovals at part throttle compared to OEM to get throttle response and grade speed comparable to OEM with same fuel injection amount.

Going from ovals to OEM bowl i have to pull timing. Not only does the OEM pistons sound horrible... Engine feels stunted/lethargic, with said timing ...something i experienced when i swapped engines in Miami

Still haven't seen MPG i got with OEM bowls with ovals, i have chalked that up for strength trade off..

Been chewing the idea of increasing CR to help off set the efficiency drop... Down side, just like timing too much CR and you kill hard parts..

Part of me wants to try 19-20:1 at what i do.. i dont think bearings would like it at 1000hp life, though i think a ~5-600hp truck would benefit from that amount of CR without self-destructing. Especially in cold climates


Nice thing about high CR, i could send them back to you and you could drop the CR by making the bowl bigger.

 

[malibu795]

2/4 rods uppers best/worst

Might put new rod bearings in

 

[PureHybrid]

Yes, new bearings for sure. Almost looks like the one has a hint of copper showing.

Have you thought about switching back to an OEM style delipped piston? Is there anyone else running an oval bowl in a strictly towing environment? Doesn't make sense to me why you would need extra timing with increased CR. Did you keep the pilot timing the same?

 

[Chevy1925]

2/4 rods uppers best/worst

Might put new rod bearings in

same 70k miles or were they reused from another time?

 

[malibu795]

Yes, new bearings for sure. Almost looks like the one has a hint of copper showing.

Have you thought about switching back to an OEM style delipped piston? Is there anyone else running an oval bowl in a strictly towing environment? Doesn't make sense to me why you would need extra timing with increased CR. Did you keep the pilot timing the same?

I haven't played with pilot timing as LMM went to uS vs degree table for lead timing.. probably cut everything back to stock settings for idle and work my way back up.

As for heavy heavy towing.. only one i know is a LML that split a piston put ovals in, along with built short block. He hauls sheds in the OH/PA/WV area

Ive thought about OEM bowl style in a mahle race cast blank at 17.5:1. Splitting two OEM cast pistons is enough for me. Honestly was expecting that to be the demise of the lbz junkyard engine

same 70k miles or were they reused from another time?

They where new when i assembled #4 in December.
It wouldn't surprise me if the debris in the babit was from bypasing the aux oil cooler system, on the side of the road, it wasn't exactly a "clean" operation at 0300.