Might as well get the crank and damper from socal diesel together if they have them available
Crankshaft Question
- Thread starter DieselDemon18
- Start date
IMO yes, the weights on the damper/flexplate are smaller than LBZ/LMM which means there is less force being exerted on the extreme ends of the crank.
Sorry Brad, I have to clarify something here: the question was "are lb7/lly cranks better than lbz/lmm cranks?"
Your answer only references external forces on the crankshaft, not the integrity of the crankshaft itself. Is it better for the life of the crankshaft to have less rotating mass on its ends because of its design limitations? I think so - but there are so many variables at play that have just as much or more impact on the life of the cranks than static mass of the bolt on parts.
Jmho
When looking at it from a systems standpoint I disagree. If I spend the $2000+ to internally balance a stock crank then they are all similar but that is unrealistic for 99.999% of people meaning it really doesn't make sense to internally balance a stock crank these days. So when looking at a stock crank for a build IMO the LB7/LLY crank has proven itself to be a better crank system (if you want to look at it that way) than the LBZ/LMM. I cannot speak on metallurgy as they've all broken and I personally don't know if the material itself changed etc.
All the stock cranks have the same fillet in the corners, all the built motors will have the same rod/piston weights (what I mean here is that there isn't a different rod/piston weight for each generation) so the only major factor, that I can deduce, between them is the mass hanging outside the engine to really ponder on "what's better".
With what we have available today it's hard to justify using an OEM used crank as opposed to a Callies. I have done it and explained why in another post (might be this thread or another) but I am willing to take that risk myself. Do I recommend a customer do that? Hell no, it's not worth it for me to recommend that path to someone who will not only come to me saying "it broke" as well as them having to pay labor/balancing to replace it if it does happen.
This is incorrect too. The rods and pistons between the generations have different mass, in different areas, creating completely different dynamic forces on their respective crankshaft, hence why they have different counter weights and balancers and flywheels.
Re-read the OP's post, both of them are going to SoCal budget rods and Mahle race casts which are not generation mass-specific meaning that anything being generation-specific is gone besides crank/damper/flexplate.
I also think you missed where I stated built engines as Carrillo/Wagler/SoCal/all other rod manufacturers only sell one rod for 01-16 and all the aftermarket pistons are generic from 01-16 and not generation-specific. If you're doing an OEM overhaul it is one thing as OEM components are most certainly differently weighted but if you're going to be mixing/matching generations of parts or going to a built motor the argument can easily be made. It's pure physics, the loads exerted on the LBZ/LML crank due to the damper/flexplate is higher than the LB7/LLY which is easily a point against logevity. Mass between the mains is a heck of a lot easier on the crank than mass outside the mains.
I understand what you are saying, but it doesn't change the statement you made that you believed lb7/lly cranks to be better because of [xyz] external forces being applied to them. That's all I was clarifying. I don't care what the OP said or what the other opinions stated were. That has nothing to do with it, honestly. I also wasn't trying to berate your opinion, only clarify it.
Well fellas not that its relevant to the discussion above but i just said the hell with it and ordered a callies crank and a 3388AF cam from SoCal. Its a big hit to my budget but ill recover down the line. At this point im just gonna live by the "buy once cry once" motto for the most part. I just want to be done with it haha, hell ive broken 3 motors in 3 years so im done experimenting with stock stuff. Just upgrade all of it where needed and roll down the road
I’d say you made the best choice for your budget and build expectations.
Not really major power, just shitty luck of the draw i guess, only making 550-600 hp, never had it dynoed
Original engine hung an injector which swelled the glow plug tip, broke it off and sent it through the intake valve.
So then i bought a supposed good used engine out of a rollover, so i tear off the heads for inspection and found the heads were junk, looks like someone milled them with a bench grinder, at that point i took it to a machine shop (which is a whole nother story time in itself) to get freshened up, upon teardown they found sheared cam and crank pins, so then i had it rebuilt, all the machine work done, new bearings, lbz rods, used lb7 pistons the were coated, main studs, melling oil pump, head studs etc.. so its running good enough, wasnt 100% right but it was good. Well about 6-8 months in out of the blue i start losing oil pressure when warm, verified issue with mechanical gauge so out it came again and back to the machine shop, they found i had spun the key to the crank gear, so another refresh it was, back together and a year or so later cruising down the road getting on to pass and pop went the engine, white smoke out the tailpipe, crazy blow by, oil everywhere so after teardown found cracked number 4 piston.
So i guess technically thats 2 motors one just broke twice. So now im building the original block and hoping to be done with it
So I've read alot about used cranks checking out good, using them in a rebuild, and not long after break.
My mind says that the steel has been fatigued in a certain matter. It's used to the beating it sees with stock balancing etc. It mags out good, gets used in a rebuild that gets internally balanced. Now the crank sees new harmonics, new loads in different areas. It's like bending a piece of metal one direction for a while, but once you go the other direction as well it gets very weak.
That's what makes sense in my head.. maybe they'd live better if balanced close to stock??
My mind says that the steel has been fatigued in a certain matter. It's used to the beating it sees with stock balancing etc. It mags out good, gets used in a rebuild that gets internally balanced. Now the crank sees new harmonics, new loads in different areas. It's like bending a piece of metal one direction for a while, but once you go the other direction as well it gets very weak.
That's what makes sense in my head.. maybe they'd live better if balanced close to stock??
You literally just said exactly what ive been thinking for the last few months but didnt wanna say because im no genius on metallurgy or engine building, so I just mostly talked with dad about it lol, hes no diesel enthusiast either. You even used the example of bending the metal one way and then back the other that ive had on my mind. I handload for my my hunting rifles, and you always have harmonics to deal with, but once you can find a load that consistently vibrates the barrel the same every time thats where you start finding dead nuts accuracy. I beat the crap out of my first engine stock crank for 130,000 miles with it having a total of 252,000 miles when a piston let go. No telling how long that factory balanced crank would have lasted... throw that crank in another engine with slightly different harmonics and boom, shed be gone in short order, It sure seems like it works that way. Of course some people would get lucky and the harmonics would be similar enough one engine to the next that they would get a decent life out of it, that person wouldnt be me. It would also explain why the horsepower level doesent seem to matter, its just luck. Mite not makes sense to yall I know my wording is very crude. Just thoughts...
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Think it was a good move going with Callies. I liked the Compstar approach with keeping stock config but better material when I first saw one. Then that first batch screwed up a bunch of builds. But like any good manufacture, they corrected the issue, even if they never came clean as to the true cause.
But as owner of the first 2 neutral balance UltraBillets off the rack, I couldn't be happier. Neither has chucked a tungsten bar at me yet.. And one of them has twisted off a 1480 driveshaft, pealed the teeth off a 12mm CP3 gear after it seized , and literally destroyed every other piece of hardware bolted behind them. Both have seen well over 5000R sustained multiple times loaded. All with about 90lbs of flywheel hanging off the back. To date, 2 of the smoothest spinning Dmax assemblies you'll ever lay your hands on. And that's not just harmonics related..
But as owner of the first 2 neutral balance UltraBillets off the rack, I couldn't be happier. Neither has chucked a tungsten bar at me yet.. And one of them has twisted off a 1480 driveshaft, pealed the teeth off a 12mm CP3 gear after it seized , and literally destroyed every other piece of hardware bolted behind them. Both have seen well over 5000R sustained multiple times loaded. All with about 90lbs of flywheel hanging off the back. To date, 2 of the smoothest spinning Dmax assemblies you'll ever lay your hands on. And that's not just harmonics related..
I had the same theory about metal fatigue due to "memory" and then switching it up, i was going to do stock crank, cam, balancer, and just a bd flex plate on stock flywheel, but i worked a good enough deal i can manage and got a callies crank, socal af cam (i was going to go 3388 standard but he gave me a better deal on a af cam) and an ati damper, still going with the bd flexplate in stock flywheel. Could i have gotten away with a stock crank? Proably especially since i had a stock crank in the mild build before when i popped a piston and the new build will basically be at the same level and the crank lived just fine. I did it for peace of mind and to have the ability to crank it up a bit should i choose to in the future, buy once cry once and be done with it
Just so no one takes me wrong I am absolutely not denying that there is a design issue, or that a narrow rod journal crank is the only sure fix. But I do think that a New Crank is the most important factor determining longevity for the guys not wanting to drop $5,500 on a crank. I also think AF cams are a great upgrade for using with new cranks, but personally I would really hesitate to ever run one on a used crank that was already used to a certain firing order, I kinda feel like you would be spending more money only to shorten the life of the crank even more vs just sticking with the stock firing order it's already used to.
ive seen it go both ways and neither one really be better than the other. if you go internally balanced or are needing a massive amount of weight changed on the crank, i would change cranks from the used one to a new one to better your chances. otherwise from an externally balanced stand point, its 6 in one and half dozen the other. i agree an AF cam is going to help bandaid it along better though.