MCummings

HOHN, I'll have to agree with you to a point.

Chris isn't the only one who runs his truck like this.

01_HO runs his truck just as hard. He hasn't seen failures like Chris has.

My 12V wasn't run as long as Chris' truck was, but it saw the same RPM, boost, and temperatures his motor did, and the pistons were in good shape. (I can't say the same for the cracked head, and bearings)

I'm still leaning towards cryo resulting to this type of failure.

Merrick

Diesel-Dan

BAD Blow-By on #6....walls are dark brown.....#4 is kinda the same...but not as bad.......#1 was the big prob......cyl wall has about .02" gouge in it...about a 1/2" wide! FOD or broken ring.......either way....no compression!

Diesel-Dan

Don....
what was the part number for the RV Pistons you were talking about....say with .030-.050 over...We are needing to get numbers and parts ordered.....and for the crank....Can you get it turned for me with the proper size bearings? Let me know...we are yanking the motor out of the truck tommrow and want to start with the machine work this week...or next. Thanks!

Dan

Don M

Dan,

I will call you at the shop tomorrow.

John_P

Mudinford:

I have gotten in on your post a little late. I see where you
are working with Don and in no way want to interfere with
that. However, I wanted to recommend Scheid Diesels
Arias Pistons to you for that engine rebuild. I now have
them in my 96' Dodge CTD 12 valve engine and am very
happy with them! You can contact Kent Crowder at Scheid
Diesel (Lafayette, Ind. Shop) if you are interested. His
toll free number is: 1-800-669-3533. They are much
stronger than the Cummins stock or marine pistons
and are high heat coated along with having their
ring grooves set lower to avoid all the heat at the
top. They are also much thicker around the wrist
pin area for added strength.

-----------
John_P

Diesel-Dan

I am open to any and all suggestions.....thanks for the info and lead...i just bought a turbo off them boys about a month ago for a cust...i think i am set up with them.....ill give em a shout.......Thanks!

Don M

John,

IMO, Forged pistons are not needed for 600 HP.

The reason I feel the RV275's would work just fine is that they are cast in a different manner and are fiber reinforced to control swelling. Using a cast piston we can keep the piston to wall clearance much lower than is ever possible with a forging. Resulting in a quieter overall operation and long term street durability. Yes, forged pistons that are hard anodized are nice, but the ni-resist ( ductile iron ) rings lands really have the long term durability advantage to hard anodized coated forgings in a diesel application.

If he feels he needs a forged piston...we have them as well. Although they are not made by Arias, but another well know manufacturer that produces literally thousands of race pistons sets per year. As the diesel industry has progressed further, the manufacturers are getting on board and really getting interested. This is helping to lower the cost for end users too!

Don~

HOHN

It IS quite interesting to me to see the failure mode. A lot of the parts looked like they just shattered!! Isn't a meltdown more typical??

I wonder if the perceived brittleness came from the cryo or from the repeated high EGTs?? That would be good to know. Is it even possible for repeated High EGT to harden the metal or change the heat-treat characteristics?

Maybe Don or some other metallurgical mind will weigh in....

MCummings

Then you would get the exact opposite of cryo?

Usually the result of high EGT is pistons that have big concave, or convex pieces broken off. Not usually shattering.

I would be interested in finding out also.

Merrick

HOHN

I'm not so sure that the Cryo wasn't the cause. The more I look at those pics, the more it looks like something dipped it in liquid N2 and hit it with a hammer..

HOHN

MCJ--

Sorry! I keep finding discussion points that I missed in earlier readings.

I agree that the OEM hardware in the bottom end is very stout.

But in a 100% all-out buildup, you can do much better. Maybe not in terms of absolute strength, but in terms of weight.

If you has Hank the Crank or Winberg whip up a billet 4340 crank for the CTD, they could probably provide equal strength at a MUCH lighter weight. Drilled throws, bull-nosing, knife-edging, full fillet, etc...

You think losing 20 pounds makes a difference to your physique? Try losing 20 pounds of rotating assembly!! *THAT* will make a huge difference.

The heavy internals of the Cummins are soon becoming the limiting factor to getting more speed. The engine will rev high with lots of torque-- it just won't do it quickly.

Ditto for Custom Rods from Oliver, Carillo, Manley, et al. Same strength, less weight.

You could probably cut 20pounds from the crank/rods/pistons in total if you went with all high-end stuff. But that's a little past the point of diminishing returns for most people in terms of $$ per HP or $$ per second ET.

Justin

Edit: fixed my crappy typos

Diesel-Dan

Honestly, I think that might be a little more extreme then the gent wants to go...but it is a good point. He just wants to have a fast truck that has a little more than the average Joe. (NO! Not the guy on TV!) In relative terms...he would be happy with a Dodge Viper rather then a McLaren F1 as far as HP / $ goes. I was just thinking of upgrading the pistons as far as strength goes and coating them for more heat resistance. For the money, i think that the 275HP RV pistons would be the best....heck, they are made by Cummins as well! Who knows.....he may be happy with just the Drag Comp box and Injectors. I know trucks like that will impress.....heck....one sent me to jail the other weekend....something about reckless driving........haha.....customers had to drive the truck back to the shop.....and I "Accidentally" Left the box on 5 out of 5 with the 180 HP injectors........ Cop was not impressed when we followed the truck back to the shop..............but i was!

Dan

MCummings

True HOHN.

I was going to be doing some "knifing" of my crank during the rebuild, but didn't.

I think just doing a mild cam, total seal piston rings, and a good balance would be great for a mild build.

Merrick

John_P

Mudinford:

I would like to add to what HOHN has posted about weight
inside the Cummins Diesel 5.9 engine. I agree with him
about that weight factor. FWIW, the old stock Cummins
pistons in my 96' weighed about 1326 grams each. The
new Scheid Arias Pistons weigh right at 1078 grams each.
IMO, that is quite a bit! After 230,000 miles my #5 and #6
pistons both had cracks across the top edge of the "keyhole"
and #5 had a spot on the very edge where the metal had
definitely began to disappear most likely from high EGT's.
I also had blow-by starting on both #5 and #6.

---------
John_P

HOHN

A weight difference of almost 250 grams on EACH piston is absolutely HUGE. Maybe not when that weight is in your hand, but when your accelerating it a couple thousand times a minute from zero to a 200mph and back, those 300grams are ENORMOUS.

What's the pistons speed of a CTD? Well, it's averaged at: stroke (inches)*RPM/6

Thus, at 3200rpm, our AVERAGE piston speed is 4.72*3200/6= 41.9 Feet/second

But it's not the AVERAGE that counts, now is it? What matters is the fastest rate of acceleration that the piston will see!! This means we have to account for the rod/stroke ratio.

Now it gets technical, but thanks to my buddy PANIC (http://victorylibrary.com/mopar/cam-tech-c.htm), we can calculate all this.

At 3200 rpm, our max acceleration is just under 29000 ft/sec^2!!!!!

Now, since F=MA, we can plug in the mass and that acceleration and compare the force.

If we take a mass of 1326 grams*29000ft/sec^2, we get a value of 38,454,000 wih whatever units.

If we take that force, but have it act on only 1078 grams, we've allowed our maximum piston acceleration to go up to 35,671!!

In other words, reducing the mass by 18.7% (from 1326 to 1078) increased maximum piston acceleration by 23%

So how much more RPM did we gain??

Well, solving PANIC's tricky formula for RPM, we get around 3550 rpm!!

Thus, shaving off 250 grams from each piston allowed us to raise rpm from 3200 to 3550 with NO INCREASE IN PISTON/ROD/CRANK STRESS

You wanna think now about what shaving 500 or more grams would do????