I was cruising around Facebook this evening and came across a post where someone dynoed a build 6.7 that put down close to 1200 HP. What I found most interesting about the post is that they made a big deal about it being a stock block. When I questioned them, I was made to understand that both 5.9 and 6.7 blocks are pushing their safe limits when over 1000 HP. I never knew Cummins blocks were so fragile, and it made me start wondering at what power level the Duramax block is in danger. I don't recall ever hearing of a Duramax block cracking, but at what power level is it necessary to fill the block or take other precautions to prevent a block failure?
Duramax block strength
- Thread starter JoshH
- Start date
I think it's just bc they are so unbalanced being an inline. No real idea of when to fill or half fill a block though. I have seen blocks crack, webbing and cylinder wall cracks...
In my mind, half fill would promote cracking at the fill level.
I have a lb7 out of a stock c4500 right now with a cyl cracked.
We ran a unfilled block with no girdle and stock caps @1400 fwhp for a Lil bit in 2015 and it junked the block. No cracks but spread the pan rails basically. So no way to fix it. Our current engine is full filled and billet mains and I noticed it has spread the pan rails some after the 2016 season at 1500 fwhp. Still going strong this year, though. We did back the power down though
I have a lb7 out of a stock c4500 right now with a cyl cracked.
We ran a unfilled block with no girdle and stock caps @1400 fwhp for a Lil bit in 2015 and it junked the block. No cracks but spread the pan rails basically. So no way to fix it. Our current engine is full filled and billet mains and I noticed it has spread the pan rails some after the 2016 season at 1500 fwhp. Still going strong this year, though. We did back the power down though
If I do another build I will be doing a half fill. I am hearing of block failures due to cylinders split.
I have a 5.9 build that I have yet to run but I cryo'd the block, crank, rods, head, etc. I think they charged around $500 to do the entire engine.
I've considered doing the DMax block as well, prior to fill and machine work.
I have a 5.9 build that I have yet to run but I cryo'd the block, crank, rods, head, etc. I think they charged around $500 to do the entire engine.
I've considered doing the DMax block as well, prior to fill and machine work.
Keep in mind a dmax will not make anywhere close to the same TQ a Cummins will at the same HP. Granted everything in the inline is stronger, the tq is the killer.
With that being said I think Ryan made a general statement regarding block strength. We are seeing 1600HP at the ground for the past 2 years without issue.
This is why the 6.4 was brought into play.
With that being said I think Ryan made a general statement regarding block strength. We are seeing 1600HP at the ground for the past 2 years without issue.
This is why the 6.4 was brought into play.
but Logan hasnt opened the engine up to see if anything is in fact dieing. makes it hard to judge if a potential problem is rising up.
from what ive seen, in any engine, if you want to be semi reliable and race competeitvely, you ought to be looking at doing all you can to a block at 1400-1500hp and up, if not change to a billet block and/or deck plate.
1000hp seems to be a gray area on what to do to a block, kinda like stock delip LB7/LLY pistons. some get away with alot less than others. in that area, it really comes down to specifics like truck weight, what its purpose is, turbo setup, and so on
That last paragraph is very true.
Some trucks may make 1000 horsepower, or at least the owners claim they do.
But there is a difference. Some trucks actually make it, AND use it. Those that truly use it, and make the engines beg for mercy on a regular basis are not gonna get by without all the necessary parts......
Sent from my iPhone using Tapatalk Pro
So how many duramax block failures have you seen or know of that weren't caused by assembly error or another part failure? It isn't something I see commonly talked about like rods, pistons, and cranks, but there aren't that many 1,000+ HP trucks running around either.
Guy I know of split his in the area above the crank. The main stud pulled down enough to split the material after a wiff a nitrous on a 10 second truck on fuel. Can't remember if it had billet Caps or not.
Sent from my XT1585 using Tapatalk
Sent from my XT1585 using Tapatalk
Our pulling engines actually never failed. They would have eventually but we're still running fine when we found the issue(pan rails spreading).
Sent from my XT1585 using Tapatalk
Yeah agreed.
But then it's not broke so why worry about it. If/when it comes out I'm sure there will be some main cap walk but that truck also sees zero street use which doesn't give the "reliability" factor any credit. It just runs 155mph every pass haha
I've never dynod it, but it was around 1000rwhp maybe a little more.
CompD calculator with weight vs. ET put it at 1058.
I had a bigger jet in when it split though