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Discussion Starter · #1 ·
So I bought a 2.6 kb from a local guy. After getting everything installed, I realized the blower pulley was much farther forward than the other pulleys. After a few days of researching and finally getting ahold of Kenne Bell, I found out it was in fact a 2.8 and not a 2.6. It took about another week to get the correct spacers to push out the tensioner and idler pulleys bracket along with the spacer for the crank pulley. Got everything installed and the factory harmonic balancer didn't work with the crank pulley spacer. Ordered 4 different harmonic balancers over the course of another week and finally found the right one.. I didn't want to spend almost $500 for the bhj harmonic balancer. All that said, it's finally done. Here are a few pics and a video of one of the dyno pulls.













VIDEO:
http://s1199.photobucket.com/user/h... Uploads/20150926_114537_zpsdpr2ifqe.mp4.html
 

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Yep, this problem has cost a few broken crankshafts. The best solution is one of Johnny's midplates, it puts the blower pulley in the proper position in relationship to the crank pulley, no spacers needed.
 

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I've searched all over and can find no direct evidence of the multiple broken cranks due to the 2.8s. I have seen on, but I have also heard of cranks broken from non 2.8L blowers. I think the best fix for this and any other blower with a very tight blower belt would be a bearing supported blower pulley bracket.
 

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I've searched all over and can find no direct evidence of the multiple broken cranks due to the 2.8s. I have seen on, but I have also heard of cranks broken from non 2.8L blowers. I think the best fix for this and any other blower with a very tight blower belt would be a bearing supported blower pulley bracket.
Besides the fact that they almost always happen on setups with a spacer? Leverage already proves that setup to be weaker than the factory style.. Doesn't seem like a coincidence to me.
 

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Discussion Starter · #8 ·
What kind of numbers did you get from dyno?
I ran out of money during my build and stuck with the stock cams so they really restricted the power. At 20 lbs it made 520/610. Going to add more boost this year and see what it does. I'm about to buy the jlp stg 3 cams and powerflow plenum from the guy that sold me the blower. That will go on this winter and be ready for spring.

BTW, looks nice.
Thanks
 

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I would consider those the extreme cases. 10in lower on a 2.8KB is really pushing it.
Also the 3.6L KB doesn't require the spacer of the 2.8L so even though it did break, I don't think the spacer was the cause.
I am not saying it can't or won't happen but it doesn't happen to every truck.

Also, how the alignment key for the balancer (point of failure on the first link) is machined/ cut causes a significant stress riser if the key is supporting the rotational load. This is typical in the way keys are cut and this can be improved upon easily with a little extra time and small die grinder with a carbide bit. The clamping force and surface friction of the balancer to the crank should be what supports that load, not the key. If the bolt is loose or nor properly torqued or the contact area is reduced then the key will start providing the support (something it is not designed to do). Even reusing a bolt that has been over torqued or stretched can be a factor in reduced clamping force.

All I am saying is that a I don't think running a 2.8L with a spacer will automatically break the crank. Pushing the hp envelope to the extreme obviously increases that risk but that goes for any blower.
 

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Who broke a crank that was running a spacer?
Every single person with a 2.8 or 3.6 KB that has broken the crank so far, has ran spacers, because up until literally the past month or so, they all required a spacer for the crank pulley.

Carmelo snapped his on his 3.6. Built54 snapped his on his 2.8. somethingnew snapped his on his 2.8, ericp broke his on his 3.6, JL has broken his before as well when he had a 2v 2.8/3.6 combos.

Now that doesn't mean EVERYONE with a 2.8/3.6 is going to snap theirs, it's a small handful that have had it happen, and there are a small handful that don't have anything extended and have snapped theirs (leach with a 2.3 whipple and no spacers), but in general throughout the history of L's running big blowers, it's usually the ones that require spacing out that are more prone to snapping a crank.

I would consider those the extreme cases. 10in lower on a 2.8KB is really pushing it.
Also the 3.6L KB doesn't require the spacer of the 2.8L so even though it did break, I don't think the spacer was the cause.
I am not saying it can't or won't happen but it doesn't happen to every truck.

A 3.6 KB does require spacers, about 1/2" whereas the 2.8 requires about 3/4". So not as far, but still spaced out further than 0". JL has new midplates though that keep the big blowers in alignment so no spacers are required.

Also, how the alignment key for the balancer (point of failure on the first link) is machined/ cut causes a significant stress riser if the key is supporting the rotational load. This is typical in the way keys are cut and this can be improved upon easily with a little extra time and small die grinder with a carbide bit. The clamping force and surface friction of the balancer to the crank should be what supports that load, not the key. If the bolt is loose or nor properly torqued or the contact area is reduced then the key will start providing the support (something it is not designed to do). Even reusing a bolt that has been over torqued or stretched can be a factor in reduced clamping force.

I do 100% agree with that, it's not one factor alone, it's a combination of them. In Carmelo's case, examining the broken crank snout up close, it appears it started as a stress fracture along the line of the keyway because it was only a single key. If it were double keyed I think it would have survived longer. But having things extended out is putting additional load on the crank snout, which is accelerating and increasing any stresses on it making it more prone to a failure sooner.

All I am saying is that a I don't think running a 2.8L with a spacer will automatically break the crank. Pushing the hp envelope to the extreme obviously increases that risk but that goes for any blower.

Correct, running a 2.8 with a spacer wont' automatically break it, but when you do push it, a 2.8 with spacers is more likely to break a crank than a 2.8 with the new midplate that doesn't need spacers

See comments in red
 

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Johnny's mid is a great solution to the problem, but it is an extra expense for sure. Jeff is going to be running Johnny's mid on his Trinity motor, with a 4.7 KB. Eric puts his touches on the mid so it is a work of art now.
 

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Hope my double key crank will hold up against s my 3.6KB.:scared003

I have couple of friends running some 2.8KB, 3.2 and 3.6kb out here in the SoCal area and haven't had a broken crank.

I would be worry about till you start bolting up a 10b lower.
 

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Johnny's mid is a great solution to the problem, but it is an extra expense for sure. Jeff is going to be running Johnny's mid on his Trinity motor, with a 4.7 KB. Eric puts his touches on the mid so it is a work of art now.
the JPS plate is an absolute work of art, but you can now get the smaller KBs (and by smaller, I mean 2.8/3.2/3.6...small compared to 4.0/4.2/4.7 lol) with a revised KB midplate design from JLP that keeps the front pullies aligned for no spaced out crank pulley.
 

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That's a good thing for sure. Allowing the Lightning guys to run the big, all blowers are big for me running my little MP, KB without the fear of the pulleys not lining up. I have always thought that using the spacers was a scary proposition.
 

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the JPS plate is an absolute work of art, but you can now get the smaller KBs (and by smaller, I mean 2.8/3.2/3.6...small compared to 4.0/4.2/4.7 lol) with a revised KB midplate design from JLP that keeps the front pullies aligned for no spaced out crank pulley.
Any idea what the JLP KB midplate costs? I have a brand new 2.8 KB LC sitting in a box. Trying to decide if I should run that or one of the other blowers I bought.
 

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Any idea what the JLP KB midplate costs? I have a brand new 2.8 KB LC sitting in a box. Trying to decide if I should run that or one of the other blowers I bought.
Not sure you'd have to call up JLP and see, I'm not sure if they've finalized pricing yet for "retro-fit" kits to swap the plate out on existing blowers.

What other blowers did you buy? Unless it's a 3.2 or 3.6 KB also sitting there, I'd slap that 2.8 on! lol
 

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I called JLP but Sue and Johnny are at a race and the other mechanics and people in the office weren't aware of the plate so I will wait until they get back.
 

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yeah NMRA @ BG was a rainy weekend, so they're actually still racing today finishing the event. JL and Sue probably won't be back in the office till Wednesday (office closed normally) or Thursday.
 
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