Dodge Cummins Diesel Forum

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-   07.5 - 09 3rd Gen 6.7L Performance Parts Discussion (http://www.cumminsforum.com/forum/07-5-09-3rd-gen-6-7l-performance-parts-discussion/)
-   -   is it true about 5.9 (http://www.cumminsforum.com/forum/07-5-09-3rd-gen-6-7l-performance-parts-discussion/471623-true-about-5-9-a.html)

burnin oil 03-23-2012 06:49 AM

6.7 has better street manners and holds its own in relatively stock truck mods. If you are going all out the 5.9 wins hands down. The internal stresses are less so the block holds together better and has less sealing issues with head gaskets. Seems like most guys are starting to dump the 6.7 after 700 HP. It can easily make that power level but the reliability just goes down. The supporting mods are just cheaper for a 5.9 and hold more power.

cummins04.5handshaker 03-23-2012 10:05 AM

Quote:

Originally Posted by 440dart (Post 4977255)
How bout you just compare the most known truck on here arron truck vs ashely blacks truck two identical trucks 5.9 vs 6.7 if i remember correctly ashelys truck had ported head cam and sidemount intake compared to a bolt on 6.7 and ashleys truck was just a couple tenths faster then the 6.7 and smoked liked a freight train and took forever to spool the turbo. Arrons truck spooled like it was stock and only put out a puff of smoke.

All things equal ported head ect the 6.7 still smokeless was a second faster correct me if iam wrong

Aaron's truck had a ZZfab intake plenum, P&P head with a cam and all the valve train goodies.. at least that's what was said about it in the Diesel Power mag. The pic showed the ZZfab side mounted intake, so the stock plenum was milled off like Ashley's truck and who's gonna mill the intake plenum off and not P&P the head..:confused013: exactly nobody.. :party018: :thumbsup:

06 tan cummins 10-29-2012 09:22 AM

Quote:

Originally Posted by Smourj21 (Post 4857803)
Well I guess I base it off how well it can be built. I have had 2 friends with 68's both of them have gone out with having just an h&s...I'm not a huge fan of electronics. You can only do so much with them...is there a reliable 68rfe out there to hold 600-800hp??


Sent from my iPad using Tapatalk

garmon diesel makes an excellent 68... In order to build a good 68 you have to have a really good understanding of how the trany works its completely different then the 48s in many ways. get a good trany tune for a 68 like the overdrive software or send your tcm to the guys at mhp and you will get good miles out of a stock 68... depending on how hard you beat it

operator62 10-29-2012 11:59 AM

Supporting mods cost the same when it comes to studs and rods. They're the same parts. You just need rods sooner powerwise compared to a 5.9. With the right tuning both can handle a bit more before needing something better. 800 on PMRs I think is a risk 5.9 or 6.7. Depending greatly on setup and tuning of course. I did 515 on Dunbar's dyno with 60 percent nozzles, bag of parts, exhaust, and smarty sw9 14me. 1/8th mile time suggests close to 560 at the wheels. Now with efi live I don't know where I am.

RAN '07@ATSDiesel 10-29-2012 02:41 PM

010 - YouTube

Diesel Duner 10-29-2012 08:30 PM

How fast? Do u have the ATS68 locking?

RAN '07@ATSDiesel 10-29-2012 08:36 PM

Those passes were in the 10.50 range. Single turbo 6.7, against twin turbo 5.9:thumbsup:

I'll have some video's up very very soon of a 68 with a lockup copilot:thumbsup::party018:

patrickATSDiesel 10-29-2012 10:35 PM

Quote:

Originally Posted by burnin oil (Post 4983575)
Seems like most guys are starting to dump the 6.7 after 700 HP. It can easily make that power level but the reliability just goes down. The supporting mods are just cheaper for a 5.9 and hold more power.

I know plenty of guys over 700hp with a 6.7. More than a few of us with stock bottom ends too :shock:

I agree with what you're saying, a 5.9 bottom end (in general, some do break with less power), but will hold a good 1000 rwhp. Beyond that, yes, rods would be a good idea.

In the performance world, there's plenty of guys/companies going to the 6.7, whether it's a true 6.7 or mixed and matched with 5.9 parts to get the best of both worlds.

I'd say H&S drag truck, with a 6.7 electronics, running 9.20's pretty much squashed the myth of these things not going fast. Along with what Aron Nick was doing with an off-the-shelf Smarty programmer and where Ryan Milliken's quad cab was. Got a few other guys shooting for mid to low 11's as well - pac_master, Ryan's single cab, and might as well throw me in there too.

Work that Ronnie Pene has done, to break things that nobody knew would break, has also taken this platform to a new level. I'm sure his truck will be an absolute monster, in Mega Cab form with a 68RFE.

It's an exciting time to have a 6.7.

burnin oil 10-30-2012 12:18 PM

Don't get me wrong. I love the bottom end that my 6.7 can put out, not to mention that there is no replacement for displacement. That said the 6.7 seems to suffer the same problem all strokers suffer from. Higher forces exerted from longer stroke. You can scream a 3" stroke gasser at 8k RPM all day long. Wouldn't want to try the same with a 4" stroke. You build the motor to withstand what you want it to do. If I wanted a long term reliable motor pushing high RPM and HP I would do the 5.9. Towing or occasional blasts into the higher RPMs the 6.7 will be just fine. It is all pysics and owners intended usage.

RAN '07@ATSDiesel 10-30-2012 01:40 PM

Quote:

Originally Posted by burnin oil (Post 5640197)
Don't get me wrong. I love the bottom end that my 6.7 can put out, not to mention that there is no replacement for displacement. That said the 6.7 seems to suffer the same problem all strokers suffer from. Higher forces exerted from longer stroke. You can scream a 3" stroke gasser at 8k RPM all day long. Wouldn't want to try the same with a 4" stroke. You build the motor to withstand what you want it to do. If I wanted a long term reliable motor pushing high RPM and HP I would do the 5.9. Towing or occasional blasts into the higher RPMs the 6.7 will be just fine. It is all pysics and owners intended usage.

This makes no sense to me. There are plenty enough people switching their 5.9 short block for a 6.7. Then you have the best of both worlds.

burnin oil 10-30-2012 01:58 PM

Yep and a few going the other way also. Basically the problem with an all out 6.7 is not the rods but the force exerted on them. There are several factors at work here. Mass, stroke, rod angle, piston hieghts, RPM of torque usage etc all add in (not sure of all that apply as I never got that far into a 6.7 build, my 5.9 is the toy and 6.7 is for towing) to make a package that doesn't like higher RPM. Watching a couple of guys on comp there seems to be one big problem at work. The 6.7 has a lower RPM power band and the pressures are killing the connecting rods, not through a weakness in rods but how the 6.7 loads them. Alot of the guys pushing 6.7s are pretty happy about EFI coming around so they can cut the low RPM torque to help the rods live and limit the amount of block shift. If the torque comes on later, like a 5.9, then you can take advantage of the larger bore and displacement the 6.7 offers without pushing the block and rods beyond their potential. Personnally on an all out build with deep pockets I would look into the 6.7 block with a 5.9 crank. Bigger bore without the worries of the rods failing at low revs and still be able to wind out the motor to 5-6k RPM. << Sarting to sound like PPump territory and not a common rail build.

RAN '07@ATSDiesel 10-30-2012 02:08 PM

Funny you say that. My stock rods held 900+Hp just fine, with a box tuner. Besides, if someone is spending 15k on a build, and they don't at least swap in a set of 12v rods they're asking for problems. A forged rod will bend before it breaks.


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