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LBZ GM Duramax Discussion of the Newest Generation Duramax and GM Trucks

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Old 02-25-2020, 11:40 AM   #1
deerefanatic

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1000 lb-ft Tow rig build - what do I need?

So, it looks like I'm going to be possibly keeping my blown up LBZ vs going through with my cummins swap. Plan for the truck was to swap in a twin turbo 12v in front of the Allison. Now looking like that's going to get major $$$ to make it work. The cummins I had to go in it was built exactly like my last 12v truck and that one made 502hp/1250tq on fuel only. It made HP peak at 1900 rpm and torque peak at 1850 rpm. I could hook to my 25k gooseneck and put the hammer down and I never saw over 1250 on the pyro.

I want the same from my LBZ... Or I'm not keeping it.

A little history: This duramax has been the biggest POS I've ever owned. Has blown headgaskets twice, and limped the transmission. Since I've owned it, it's only had a fuel mileage EFI Live tune, that I switched to stock whenever I towed. I have a built allison in it now (no billet, but Alto G3 clutches, shift kit, shimmed pump pressure regulator, cutback valve, etc).

I'm looking at rebuilding the engine myself as I work as a heavy truck mechanic, and I've built all my 12v cummins motors over the years myself.

I'm planning on doing:
LB7 pistons, delipping them myself on my lathe and then sending out for ceramic coating
New bearings, gaskets.
Already has EGR delete
Stock turbo + S475 twins? Plan to build my own kit. (I've built all my cummins twin sets over the years)
Will I need rods for this? I'm planning on 1000-1200 ft lbs torque. I don't drag race, and dont sled pull. Daily driver/tow rig duty only.
Injector tips?
Already has a lift pump with external filters. Deleted the whole stock filter housing.
What else? I don't see the need to key the crank, cam, water pump etc as I'm not going to be revving this girl up. Only time it's ever been over 3000 rpm was engine braking down grades.
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2006 Chevy 3500 CC Dually LBZ - Died again
2005 Mercedes E320 CDI - Best car I've ever owned
2004 Chevy 3500 8.1 - Gas hog
88 Chevy C3500 Cummins, RIP
84 Mercedes 300SD Diesel. Old reliable..
64 Oliver 1850 Cummins. 227hp, for now...
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Old 02-25-2020, 08:26 PM   #2
Empty_Pockets
 
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You have the stronger rods in the lbz vs previous years but they are known to bend around the 1000++ ft lb mark. Some guys have ran 6 to 800 hp through them with good luck but with bigger singles and keeping the torque low. So thats your call. With the luck youve had, I would do carrillos or at least crowers. Obviously send the heads off or get new ones. Get mahle gaskets and throw 425s in there and you shouldnt have head gasket issues again. Ive always been told the coating on the pistons just burns off and to pass on it. Get the plastic impeller water pump instead of welding or pinning yours. Built transmission/tune/lift pump trucks will do 500/1000 give or take. If you are compounding off the stocker i would suggest at least doing some 45% overs to help keep the pw down and run cooler. Look into getting an aftermarket oil cooler also.
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2004 lb7 cc flatbed stockish/daily
2012 ccsb cummins Race/puller.
Currently broke and its got damn carole baskins fault!
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Old 04-29-2020, 01:06 PM   #3
anotherduramax

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The 2020 L5P oil cooler can be retrofitted to work, like posted above Mahle wavestopper head gaskets seam to be the go to, I would look into Socal Diesel street connecting rods.
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Old 04-29-2020, 02:08 PM   #4
JWhite
 
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I agree with the above, oil coolers need some help on these trucks if you tow on a hot tune.

I would add LML cooling nozzles, I'd go with the Mahle Motorsports pistons instead of screwing around with LB7 slugs and coating them. 475 over stock turbo will work well, LBZ rods will handle 1200 lb-ft but the tq peak won't be anywhere near 1900 rpm. If you want aftermarket rods Socal diesel has a budget line that he rates very well.

If you buy the Motorsports pistons, make sure they send you the #42160 ring set with the SS top ring. They were sending the #41909 that has a softer top ring for the forged pistons.
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