Author Topic: Recondition a duramax engine (Read 1413 times)

Flyin6 · « **on:** July 18, 2020, 09:22:44 PM »

Lets talk about what would be the necessary steps to recondition a duramax engine and build it to reliably hold 600-700 HP in my Suburban application.

Tex has stated often that the recipe consists of using a LB7 short block and turbo, but add LLY heads to it to get the injectors from beneath the valve covers.

And here is what I currently have going.

I have located a complete LB7 engine and trans which is still in the donor truck. It cranks but will not start. It apparently did run when the truck was parked a year to 18 months ago.

If I move on that one, it will include the entire harness(s) the ECM, the FICM, the TCM and maybe some other stuff like the intercooler.

Now this is going to be expensive, so I cannot go too crazy with all sorts of exotic parts. An oil pump is $300. An upgraded turbo is $3000, trans is $5000

I am hoping to tear it down to find a good reciprocating assembly that I would only have to add rods, rings, bearings, and get the block all looker over, maged, line honed and little else.

I will purchase reman LLY heads, then put a few coins into larger injectors.

That's the plan I am looking at right now.

I'd like to draw on everyone's experience here

oklawall · « **Reply #1 on:** July 18, 2020, 09:53:18 PM »

Boss,

Can't say that I have a bunch of knowledge on this but from personnel experience and before you jump into the deep end make sure you have a machine shop that will work the block over for you. Living in Oklahoma for my son 2005 we couldn't find a machine shop that would run the cylinders, they said that they would try but would take no responsibility if they damaged the block we had to go to Dallas TX to find someone that would work it over and had experience and would stand behind their work. I would also check the front cover they are made of unattainemum. The boy's truck has had issues with (sorry don't know the official name for them) the little nozzles that spray oil on the bottom side of the pistons, he had to replace 2 when he rebuilt the engine and about a year after found another one that was broken.

stlaser · « **Reply #2 on:** July 18, 2020, 10:19:26 PM »

6.7L cummins.......

TexasRedNeck · « **Reply #3 on:** July 18, 2020, 10:22:40 PM »

Wagner street rods. LB7 pistons and crank. Keep the rest stock with 30 or 40 overs and a 64mm cheetah stealth. Should get you where you want to go.

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KensAuto · « **Reply #4 on:** July 18, 2020, 11:57:07 PM »

Wait, I thought the boss was cutting back on projects?
Might as well sell the burb off in a thousand pieces and scatter it across the country.

Sorry. Can I at least qualify for unemployment this time?
Severance package?

stlaser · « **Reply #5 on:** July 19, 2020, 12:23:34 AM »

Farmer Jon · « **Reply #6 on:** July 19, 2020, 08:09:04 AM »

Quote from: stlaser on July 18, 2020, 10:19:26 PM

6.7L cummins.......

Im a Chevy man through and through but I agree with this. Until I sold mine we had 2 duramaxes 07 classic and a 2013. We also have 2 dodges. Second gen 12 valve cummins and 09 with the 6.7 in a single cab dually. The 6.7 deleted with a 35 hp tow tune out performs the duramax in every way. Near 20 mpg pulling an empty 30 ft goose neck trailer. It is a beast.

My $.02 if I were doing it I would go with the cummins.

Flyin6 · « **Reply #7 on:** July 19, 2020, 02:56:42 PM »

Quote from: Farmer Jon on July 19, 2020, 08:09:04 AM

Quote from: stlaser on July 18, 2020, 10:19:26 PM
6.7L cummins.......

Im a Chevy man through and through but I agree with this. Until I sold mine we had 2 duramaxes 07 classic and a 2013. We also have 2 dodges. Second gen 12 valve cummins and 09 with the 6.7 in a single cab dually. The 6.7 deleted with a 35 hp tow tune out performs the duramax in every way. Near 20 mpg pulling an empty 30 ft goose neck trailer. It is a beast.

My $.02 if I were doing it I would go with the cummins.

OK, for the sake of discussion, Jon, how would I do that? The 6.7 is a common-rail engine with its own electronics. How would someone get that to interface with the old style chevy can-bus/OBDII?

Farmer Jon · « **Reply #8 on:** July 19, 2020, 02:59:04 PM »

I have no idea.

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Flyin6 · « **Reply #9 on:** July 19, 2020, 05:19:33 PM »

Quote from: Farmer Jon on July 19, 2020, 02:59:04 PM

I have no idea.

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It may be possible, one shop has done it, but the difficulty and uncertainty factor for an electronic Cummins is off the chart.

Flyin6 · « **Reply #10 on:** July 19, 2020, 05:25:12 PM »

Quote from: TexasRedNeck on July 18, 2020, 10:22:40 PM

Wagner street rods. LB7 pistons and crank. Keep the rest stock with 30 or 40 overs and a 64mm cheetah stealth. Should get you where you want to go.

Sent from my iPad using Tapatalk

Quote from: TexasRedNeck on July 18, 2020, 10:22:40 PM

Wagner street rods. LB7 pistons and crank. Keep the rest stock with 30 or 40 overs and a 64mm cheetah stealth. Should get you where you want to go.

Sent from my iPad using Tapatalk

So, lets get into this a little deeper.

My first question is why do I have to start with a LB7 block, why not a LLY, LBZ, LMM or even LML?

Can't one use the LB7 wiring harness on any block as long as the top end stays early as in LLY?

I am just not seeing why I'd need to opt for a weaker bottom end which lacks the refinement of the later generations...???

Flyin6 · « **Reply #11 on:** July 19, 2020, 05:26:57 PM »

Looking around, I secured a LB7 engine which ran, but there is an LLY, a LBZ, and a LMM engine also for sale. So the opportunity is out there for about anything. Plus the LB7 engines all have 300-400K on them whereas the LMM is a bit over 100K

KensAuto · « **Reply #12 on:** July 19, 2020, 05:30:57 PM »

Sounds like Charles has researched this more than the rest of us but pretty sure the lb7 harness won't work with updated injectors, not that that matters if you're having a harness made.
I also thought the LML was the strongest bottom end out of the available options.

stlaser · « **Reply #13 on:** July 19, 2020, 06:03:15 PM »

Quote from: Flyin6 on July 19, 2020, 02:56:42 PM

Quote from: Farmer Jon on July 19, 2020, 08:09:04 AM
Quote from: stlaser on July 18, 2020, 10:19:26 PM
6.7L cummins.......

Im a Chevy man through and through but I agree with this. Until I sold mine we had 2 duramaxes 07 classic and a 2013. We also have 2 dodges. Second gen 12 valve cummins and 09 with the 6.7 in a single cab dually. The 6.7 deleted with a 35 hp tow tune out performs the duramax in every way. Near 20 mpg pulling an empty 30 ft goose neck trailer. It is a beast.

My $.02 if I were doing it I would go with the cummins.
OK, for the sake of discussion, Jon, how would I do that? The 6.7 is a common-rail engine with its own electronics. How would someone get that to interface with the old style chevy can-bus/OBDII?

Call DCS and speak with them is probably your best bet. Problem is you have a gm vehicle, buy a ford and it’s not nearly as difficult (say an excursion). I’m not sure exactly why you want to repower a functioning (expensive mods btw?) modified vehicle anyhow? Sorry, but I just don’t see it. Just because you can never reflects that you should.

Flyin6 · « **Reply #14 on:** July 20, 2020, 10:33:21 AM »

So I've researched for hours now and I can't find nor see any reason why the short block matters at all afom 01 LB7 all the way to 2010 LMM. Actually there may not be an issue with using a LML or a LGH short block either, which would be my first choice since the LML's got strongerer than earlier motors.

But, having said that, just using a LB7 would be fine as these motors have easily supported 1200HP and more with appropriate modifications. For my needs, around half that power level the LB7 seems to be just fine.

But I need to research some more

I can see upgrading the rods and adding some Mahl pistons and maybe even that switched up firing order camshaft. Seems all duramax engines can break the crankshaft at the first journal of pushed too far,, but with the new firing order, that weakness goes bye-bye.

Sammconn · « **Reply #15 on:** July 20, 2020, 10:46:09 AM »

There was something about the LB7.
I do remember something about it as well.
But that was also before the LMM was a thing too.

It may be a cooling port/jacket thing too.
I don’t know anything about what changes were made with water jacket etc.

I also don’t know as I seen it in passing and didn’t have the need.

Flyin6 · « **Reply #16 on:** July 20, 2020, 11:13:18 AM »

Quote from: Sammconn on July 20, 2020, 10:46:09 AM

There was something about the LB7.
I do remember something about it as well.
But that was also before the LMM was a thing too.

It may be a cooling port/jacket thing too.
I don’t know anything about what changes were made with water jacket etc.

I also don’t know as I seen it in passing and didn’t have the need.

I have researched enough to say the LB7 all the way to the LML use identical blocks (I mostly think...like 90% sure) The internals changed a little along the way but not very much at all. Rods got stronger with increasing HP, and the manner of balance changed from LBZ north, but the block is more or less the same.

It seems that Red Neck is correct in saying build a LB7 block and crank, aftermarket rods and better pistons and you'll have something much stronger than the mighty LML. The LB7 heads were a major problem as their injectors were surrounded with coolant and could leak both fuel and coolant, and were faulty. The next gen LLY fixed all that and that motor and the LBZ is essentially the same except for an injector change and a tune change.

I am seeing that what I am planning to build is actually very mild in the D-Max world. The cut off line is really up around 1,000-1,200 HP where exotic stuff starts to become mandatory.

For my lower power plans, a good rebuild is all that is really needed, along with adaptive wiring, a good turbo and injectors along with the LLY or better heads.

I think this is doable and getting easier with companies building wiring looms which fit what cha got into whatcha own.

TexasRedNeck · « **Reply #17 on:** July 20, 2020, 03:25:42 PM »

That’s my plan Don. The rods are the weak link in the LB7 rotating assembly. The get bendy around 650-700 depending on the pulse width and timing. Oversized injectors help that a lot but I’d still replace the. Lots of truck pull guys have run heavily modified LB7s in competition. The LML block is somewhat stouter in the webbing area but again a non issue at the power level you want to run. My LB7 with lift pump better wastegate in the turbo and dsp 5 runs really hard and I’d say it outran my LML but the LML was dragging around another 2000+lbs.

Alt firing cams are generally for those approaching 1000hp but there is still some evidence that the alt firing cam doesn’t solve what they thought it solved. LB7 pistons are pretty stout for a 600-700 hp build but by all means fingers or Mahle would be fine. The LB7 ficm has been shown to run the LLY injectors just fine and performance mfgs now have plug and play injector harnesses to make it easier.

As soon as I find a shop I trust I plan to have the LB7 block I have machined to spec 20 over and start slowly gathering the parts. My LB7 only has 197k on it so I should be ok for a while.

My autocorrect went crazy On the other post. Wagler is the brand of rod I would run. Good to 1000hp much cheaper than Carrillo

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Flyin6 · « **Reply #18 on:** July 20, 2020, 08:32:12 PM »

Quote from: TexasRedNeck on July 20, 2020, 03:25:42 PM

That’s my plan Don. The rods are the weak link in the LB7 rotating assembly. The get bendy around 650-700 depending on the pulse width and timing. Oversized injectors help that a lot but I’d still replace the. Lots of truck pull guys have run heavily modified LB7s in competition. The LML block is somewhat stouter in the webbing area but again a non issue at the power level you want to run. My LB7 with lift pump better wastegate in the turbo and dsp 5 runs really hard and I’d say it outran my LML but the LML was dragging around another 2000+lbs.

Alt firing cams are generally for those approaching 1000hp but there is still some evidence that the alt firing cam doesn’t solve what they thought it solved. LB7 pistons are pretty stout for a 600-700 hp build but by all means fingers or Mahle would be fine. The LB7 ficm has been shown to run the LLY injectors just fine and performance mfgs now have plug and play injector harnesses to make it easier.

As soon as I find a shop I trust I plan to have the LB7 block I have machined to spec 20 over and start slowly gathering the parts. My LB7 only has 197k on it so I should be ok for a while.

My autocorrect went crazy On the other post. Wagler is the brand of rod I would run. Good to 1000hp much cheaper than Carrillo

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Yea, this plan seems to be the best for a driver.

I just got an email back from DMax Swaps inc...said they do not support swaps into modern vehicles.

Bummer

Who else mods the harnesses to make this more of a plug and play??

TexasRedNeck · « **Reply #19 on:** July 21, 2020, 07:33:13 PM »

Don, my understanding is you don’t need any aftermarket parts to make the swap. All the parts from a 2500HD with Dmax interchange. I know the cluster has to be changed and I’m guessing BCM,ECM, FICM and all the harnesses from the firewall out. The only aftermarket part you will need is the injector harnesses to run the LLY injectors off the FICM from the LB7.

My suggestion is to find a complete LB7 2500/3500 as a donor and start swapping parts

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Flyin6 · « **Reply #20 on:** July 21, 2020, 09:29:49 PM »

Quote from: TexasRedNeck on July 21, 2020, 07:33:13 PM

Don, my understanding is you don’t need any aftermarket parts to make the swap. All the parts from a 2500HD with Dmax interchange. I know the cluster has to be changed and I’m guessing BCM,ECM, FICM and all the harnesses from the firewall out. The only aftermarket part you will need is the injector harnesses to run the LLY injectors off the FICM from the LB7.

My suggestion is to find a complete LB7 2500/3500 as a donor and start swapping parts

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Thanks for the info.

So far I have agreed to purchase a complete engine/trans from an 01. Seller is including the entire wiring harness from the firewall forward. That is my start point. From there I will rebuild the engine first while I continue to source parts to make the swap happen. When I get closer I'll have the trans converted to a six speed and built.

It would be crazy if I could just plug and play with only the LLY injector harness.

Flyin6 · « **Reply #21 on:** July 25, 2020, 11:03:07 AM »

OK, I'm gettin' some good advice and help from the membership here.

Have a bit of recovery to do, then I can drive down and pick up the donor motor/trans

So lets focus in on a 600-700 HP build of this hybrid motor.

I am planning on the LB7 short block having been freshened up. I'll go with the recommendation of stronger rods and the lower cost Mahl pistons. I don't see paying another grand for forged units at this relatively low power level for this motor. I will probably go with bottom end and head studs, new oil pump, maybe boring and line honing, balancing and crank polishing. Not sure on some of that, if the motor checks out OK, then I may not go too crazy with overkill.
Heads: Right now the LLY, because the LB7 FICM is known to drive them with some software changes, but the jury hasn't decided that entirely. I mean if LML heads fit LLY injectors then...Right now I think not, but if I'm buying heads why not buy the best.

One thing I haven't sorted is the transmission. I need to run the 6-speed because of the 4.88 cogs. I need that .62 OD to be able to cruise at some realistic speeds. But the 6 speed showed up after Can-Bus in the LBZ, and I don't know if I can get an LB7 ECM to chat and play friendly with a LBZ or later generation TCM.

Thoughts and ideas...even from daves??

TexasRedNeck · « **Reply #22 on:** July 25, 2020, 02:10:07 PM »

I believe suncoast has all the stuff to make a 6 speed conversion. I don’t think you can drop a later model 6 speed in it. It has to be the conversion for the reasons you stated.

https://www.thoroughbreddiesel.com/suncoast-5-6-speed-conversion/

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KensAuto · « **Reply #23 on:** July 25, 2020, 05:38:08 PM »

Boss, the best advice you got, you have ignored. Still love you though.

Flyin6 · « **Reply #24 on:** July 26, 2020, 10:16:16 AM »

Quote from: TexasRedNeck on July 25, 2020, 02:10:07 PM

I believe suncoast has all the stuff to make a 6 speed conversion. I don’t think you can drop a later model 6 speed in it. It has to be the conversion for the reasons you stated.

https://www.thoroughbreddiesel.com/suncoast-5-6-speed-conversion/

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Copy that! I researched last night and came to the same conclusion on the Ally. So if it all goes well, I should have the thing this week, engine and trans.

Flyin6 · « **Reply #25 on:** July 26, 2020, 10:17:52 AM »

Quote from: KensAuto on July 25, 2020, 05:38:08 PM

Boss, the best advice you got, you have ignored. Still love you though.

Kenneth!

What have I ignored (most recently)?

You want to keep it a gasser?

Briggs and stratton

Or pull the 5.9 Isuzu diesel out of my Kobelco?

Flyin6 · « **Reply #26 on:** July 26, 2020, 10:27:15 AM »

So here's what I have learned so far:

It seems the engines making the most horsepower are actually the LB7's!

Aside from having a poor injector location design, the LB7 engine with the factory heads would easily get the job done. I should consider, as well, just keeping the architecture all LB7. Not that I am going to go that route, but it bears consideration as I wouldn't have any adapter harness to mess with.

There are improved LB7 injectors and injector retainers as well as injector cups so that issue has been sorted. I would be starting out with what is, effectively, a new engine.

The LLY heads and those injectors are certainly a strong consideration, but as I have discovered, not a necessity to getting this transplant up and running.

Tex mentioned the trans conversion. My trans guy confirmed it can be done using the 5 speed with a six speed valve body and some voodoo. Researching it, I discovered the kits that transform the five to a six speed with foolery above the comprehension level of crusty old me. So I think I'll just do that.

The engine seems to come down to a good rebuild, rods, good pistons, good fasteners, some machining and mostly stock parts to build a foundation, and let the injectors, software, and a good turbo or two do the heavy lifting.

Still going to be expensive, but well within the realm of possible.