Lb7 limits

[OleBlackyLBZ]

My lbz went like this:

Bought bone stock with 116,000 miles.
Tuned to 400 hp around 120,000 miles, drove it like I stole it for a couple years
At 170,000ish miles had the trans built and ran it hard for a while at 475hp, wouldnt make 500+ like it shoulda due to weak injectors.
Put the danville 65 on around 200,000 miles and paired with the weak injectors it made 580 on danvilles dyno and I drove the crap out of it until a piston let go at 252,000.

Personally, I think your "probably" okay on tune 4, especially if you've already been running it you can probably get by for awhile. I would for sure leave tune 5 for later... and use tune 4 only when you feel like you need it.

 

[Bdsankey]

It was and still is. Over 260,000kms (161,000+miles) on it now. Still on stock headgaskets *knock on wood*.

That isn't saying much tho. The failure point on the earlier trucks had failures mainly related to the gasket construction itself. The factory head bolts are typically stronger than any of our OEM bottom ends can handle.


Your sig also states an LMM which has a stronger rod than an LB7/LLY but a weaker OE piston.

 

[LSxBakakos]

08lmm if it makes ya feel any better my buddies lmm lived with s475 over stock w/stock head bolts for 5 years/100k and was abused pretty hard, rolling burnouts with a skid steer on a trailer kind of hard. Broviak had done the tuning and it was almost always living at 681/1387. That truck did not skip a beat or ever have a failure. As bdsansky said I know the lbz+do have weaker pistons and stronger rods and that's news to me that they changed the head gasket design. Always wondered why so many went as long as they did without needing gaskets/studs but that now answers it

 

[08lmm72mm]

That isn't saying much tho. The failure point on the earlier trucks had failures mainly related to the gasket construction itself. The factory head bolts are typically stronger than any of our OEM bottom ends can handle.


Your sig also states an LMM which has a stronger rod than

I won't argue with you. I have been brought up with diesels since I was a kid and I've been taught to warm these engines up before driving them and I monitor my oil temp never letting it get much past 200. It's either how I've taken care of it or dumb luck

 

[08lmm72mm]

08lmm if it makes ya feel any better my buddies lmm lived with s475 over stock w/stock head bolts for 5 years/100k and was abused pretty hard, rolling burnouts with a skid steer on a trailer kind of hard. Broviak had done the tuning and it was almost always living at 681/1387. That truck did not skip a beat or ever have a failure. As bdsansky said I know the lbz+do have weaker pistons and stronger rods and that's news to me that they changed the head gasket design. Always wondered why so many went as long as they did without needing gaskets/studs but that now answers it

That does give me more confidence lol. Oh for sure the lmm platform has better rods and headgaskets. Just like everyone has said in here though at these power levels it's a roll of the dice.

On another note and I'm not sure if there is alot of certainty in it but I read an article about a business owner that owned over 250 duramaxs as fleet work trucks and he said he went through alot of broken crankshafts on them and one of the ways he found to potentially avoid it was to change out the pulsation dampner at 150,000 miles. Once he did that the rate of broken cranks in his work trucks pretty much quit.

 

[LSxBakakos]

Granted I was just only an engine assembler, not the guy doing the balancing/machine work. With these being externally balanced rather than internal i personally I wouldn't take the chance but thats just my opinion. Maybe there's truth behind it or someone can chime in on that. From the gas world external balance needs the flex plate and dampner both to be on the crankshaft, any weighted difference I would think could actually throw it off balance. Balancers do go bad and considering the heat soak these engine bays see and the amount of vibration diesels produce maybe there's truth behind them separating/coming out of balance. Did he specify wether he was running an ATI or fluiddampner? Or some other brand?

 

[08lmm72mm]

Granted I was just only an engine assembler, not the guy doing the balancing/machine work. With these being externally balanced rather than internal i personally I wouldn't take the chance but thats just my opinion. Maybe there's truth behind it or someone can chime in on that. From the gas world external balance needs the flex plate and dampner both to be on the crankshaft, any weighted difference I would think could actually throw it off balance. Balancers do go bad and considering the heat soak these engine bays see and the amount of vibration diesels produce maybe there's truth behind them separating/coming out of balance. Did he specify wether he was running an ATI or fluiddampner? Or some other brand?

Pretty sure from memory it was a stock balancer (oem, dayco, etc)

 

[Bdsankey]

Granted I was just only an engine assembler, not the guy doing the balancing/machine work. With these being externally balanced rather than internal i personally I wouldn't take the chance but thats just my opinion. Maybe there's truth behind it or someone can chime in on that. From the gas world external balance needs the flex plate and dampner both to be on the crankshaft, any weighted difference I would think could actually throw it off balance. Balancers do go bad and considering the heat soak these engine bays see and the amount of vibration diesels produce maybe there's truth behind them separating/coming out of balance. Did he specify wether he was running an ATI or fluiddampner? Or some other brand?

Pretty sure from memory it was a stock balancer (oem, dayco, etc)

It's very likely that his dampers were wearing out. At 150k miles and unknown engine hours I wouldn't be surprised if they started to separate. The OEM damper does a pretty good job for OEM RPM/power ranges.

 

[08lmm72mm]

It's very likely that his dampers were wearing out. At 150k miles and unknown engine hours I wouldn't be surprised if they started to separate. The OEM damper does a pretty good job for OEM RPM/power ranges.

That's what I'm thinking. My dowel pins in the crank for the balancer and oil pump gear were almost sheared at that mileage so we put new pins and a new balancer on. Wouldn't be surprised if the dowels are a factor in broken cranks aswell.