Melted #6, Rebuild Plan

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yfz450_0569

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Ok so I melted my #6 piston, messed up the valves, and the injector tip. I've already got my head at a machine shop in town and they said it's fixable with new valves on #6 and checking the rest of the head. The injectors are sent off to Shane at Motorsport Diesel for either new nozzles or as cores towards rebuilt.

Now for the block, would it be best to get it bored like .020 over on all cylinders or just bore and sleeve #6? I'm leaning towards the boring all of them .020 over if that's enough to fix #6. I'm doing all 6 new pistons, probably getting a rebuild kit from a shop here in town.

My max power levels will be 600-700 hp, and I wouldn't mind hitting 3500 RPMs safely. 4K is probably more hassle than it helps? All I really plan on upgrading is head studs, 50-100 hp bigger injectors, and maybe a cam, push rods, and springs (if I can get by with nozzles on the injectors and don't have to spend the money on new ones). Is there anything small that I'm missing while I'm in the motor? I plan on doing a nearly stock rebuild.. if it's too much extra stuff to do, I would rather just back off a little on the power levels. A few small things I've thought of were drill, tap/thread, and plug the freeze plugs in the head, and block of the rear freeze plug if that's worth it.
 
Do them all .02 over, get a set of 12valve/early 24valve rods, put some arp rod bolts in them, toss in arp main studs, I wouldn't do a cam at that power level, block the rear plug for sure, head plugs aren't a bad idea but do add a bit of cost. The rods and arp hardware is the most important thing. Mixed with a quality rebuild and good tune the engine will last many many miles. even at 700hp. Call Jeff at Mumau Diesel For you rebuild kit. He is hands down the best guy to order engine parts from.
 
Fullboarcummins said:
Do them all .02 over, get a set of 12valve/early 24valve rods, put some arp rod bolts in them, toss in arp main studs, I wouldn't do a cam at that power level, block the rear plug for sure, head plugs aren't a bad idea but do add a bit of cost. The rods and arp hardware is the most important thing. Mixed with a quality rebuild and good tune the engine will last many many miles. even at 700hp. Call Jeff at Mumau Diesel For you rebuild kit. He is hands down the best guy to order engine parts from.
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I've got a local auto parts store I can get the rebuild kit for just under $1K.. is there a chance it's a different brand of lesser quality than Cummins? I might try that company also..

I hadn't planned on doing anything with the connecting rods, but maybe I'll do that instead of a cam. Maybe I should rather do a few little reliability things rather than the cam right now. I've just always wanted one so bad and now the motor is apart...

The cam is probably more for the efficiency factor and in cylinder EGR that just bugs me.. I know it would help me much. If I don't do the cam, should I still do valve springs? Would the stock cam and push rods be good for many more miles?
 
I wouldn't worry about switching rods unless there is the slightest glimmer you'll be over 900-1000 hp one day.
 
Is there any issue with used 12V connecting rods or should I go new with those too? I've heard about them being stronger and seen people buy them used.. but not sure if that's taking a chance or not. I've seen them on eBay for $150 easily.
 
He was referring to connecting rods. Cracked cap rods tend to fail extraordinarily, where previous rods would bend before breaking. I would have no worries running the cracked cap rods on a 5.9 making less than 900hp.
 
TheBigNasty said:
He was referring to connecting rods. Cracked cap rods tend to fail extraordinarily, where previous rods would bend before breaking. I would have no worries running the cracked cap rods on a 5.9 making less than 900hp.
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So your opinion on the rods is to stay stock..? How about ARP rod bolts like the guy above said? From what I've read, I don't have a problem staying with stock connecting rods, but if used are fine, I can get them for cheap enough to where I could consider that too.
 
I'm saying that a stock rods are fine. If you find a set of older rods and can fit them in the budget, it's a good idea, but not necessary.
 
Ok so the machine shop said #6 had to be sleeved because of the damage and went ahead and honed the rest and said it was all good at standard size.. is this fine or should I get all 6 bored .020 over now yet for an extra $135?
 
So the little hone is not really a loss of compression or anything worth thinking about? Maybe I'm a little to particular with the least important things sometimes...
 
Personally, I would replace the CR rods with a set of 12/24v rods in anything of mine. I would be worried about blowing a HG, hydro locking the motor and sending a rod through the side. You can get a set of used rods for $150 which is pennies to a good engine build.

I doubt you are getting Cummins parts for under $1k, I would call Jeff and get Cummins parts. As far as an over bore piston I would check cylinder roundness and go from there. I would not overbore unless you needed to.

Also be sure to check the head and block for flatness and have them decked with a good finish if they are out at all.

I agree with Brandon that they can take the power, but for me $150 is worth the piece of mind of knowing if something goes wrong they will just bend and not destroy everything.... hopefully. LOL
 
SPEEDSHIFT said:
Personally, I would replace the CR rods with a set of 12/24v rods in anything of mine. I would be worried about blowing a HG, hydro locking the motor and sending a rod through the side. You can get a set of used rods for $150 which is pennies to a good engine build.

I doubt you are getting Cummins parts for under $1k, I would call Jeff and get Cummins parts. As far as an over bore piston I would check cylinder roundness and go from there. I would not overbore unless you needed to.

Also be sure to check the head and block for flatness and have them decked with a good finish if they are out at all.

I agree with Brandon that they can take the power, but for me $150 is worth the piece of mind of knowing if something goes wrong they will just bend and not destroy everything.... hopefully. LOL
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I've already called Jeff.. quoted me a kit with Clevite pistons that he said was a little cheaper than the actual Cummins kit, told him my plan of 600-700hp and he was just like yeah that's common these days.

That is a pretty good point about the connecting rods.. I just didn't know or think about the older rods bending vs snapping. I've personally seen a connecting rod snap and hole through the block on one of my dad's trucks.. a stock 6.7 with around 20K miles!!

The guy at the machine shop said he honed the other 5 to make sure they were cleaned up.. I'm guessing that means they would be good. He didn't take anything off the top of the block or off the head, I should maybe ask him to be sure they were good n straight.
 
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I would def have them checked. Now is the time to do it, may save you a ton of work and money later.
 
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