Double Yellow's Company Driver to Independent Thread

When I had the injector cup and heads replaced last year on my N14, I seriously contemplated doing an inframe. I had the money at the time and figured it would be one of those, while I'm in there deals. I wasn't getting anywhere close to what you are getting in MPG, but I was holding steady at 8.75 and wanted to breach the 9's (with 1.5 million miles). The shop talked me out of the inframe for that reason and I'm glad they did. Personally if you are getting that fuel mileage and aren't using oil, I wouldn't do the inframe. Only thing I'd have done different would be to replace the only injector acting up (if it is that and not the harness) as my father had an injector issue when he owned my truck and the shop talked him into doing all 6 instead of just the one acting up. It hasn't been the same since (idles rough) and had to replace 2 injectors 3 different times as they had installed faulty injectors.
What was the blow-by like? That would be another reason to decide if you should do the inframe or not. Personally though I wouldn't because this seems like you have a great running truck DY!

 

My 2 cents worth (tax free today) is.........
If It's got some Blowby,
& you've got the head off It, & can afford the Inframe (even if you can't)
INFRAME IT..
Also, If It was My truck (which it isn't) while you have the Head off.
I'd be checking all the valve seats & faces plus replacing all the valve springs as well...

Far easer & cheaper to only pay once for the labour...

 

This. Hopefully by now you've either had a look at it, or soon will. The only additional thought with this is with observed wear. Whether it's worn off cross-hatching or heat/scratches on the cylinder noted as "scorched," it's not going to improve over time. It also may not be something that happened last week. I guess my point is, consider what you have when you see it, and then think about how much piece of mind you'll have knowing that's there versus new parts. Outside of the parts, an in-frame bills out at about 40 hours. You're already into a cylinder head, usually at about 20 hours. Personally, I'm a "fix it one time" kind of guy, so tend to (and have) opt for more now with lower risk of more downtime and another round at the shop later. Someone else might drop one injector in there and run it another 500k. I'm never "that guy," so I don't even take the chance any more.

With respect to low rpm cruise, I doubt that's an issue. Even if it were, I don't think you've put enough miles on it to do anything substantial. The risk is with high load at low rpm. That gives you high egt and does the damage. This came up on the KR quarter million dollar glider fiasco. The owners routinely lugged it up grades because they were told it would be ok. Of course that came out as a series of issues with the build. However, there had been signs of high temp problems early on.

Without knowing for certain about the injector failure indicated (harness or injector), it's impossible to say if it had anything to do with the dilution flag. That may become more apparent now that the head's off, and I would expect you mentioned to the shop that fuel dilution result you had.

I think you'll find the peanut gallery divided about 50/50 on changing one faulty injector only, or replacing as a set. My opinion is: if at high mileage there is one failing, keeping the other five will be a more risky bet than changing all six and getting a faulty one in the new set. Simple as that. There's other factors supporting both choices. Don't fix it if it ain't broke, injector balance, and so on. I'm not as sensitive on those things as I would be with the risk of future downtime.

The blow-by measurement would be taken on a dyno with the engine under load. All will have some puffing out the breather while idling. I spent a bunch of time doing internet searches a while back trying to find standards, and they're all over the place. The consensus I reached was that an acceptable measure was less than 1" for most engines, less than 2" on a CAT ACERT. The latter due to the twin turbo and IVA setup. Supposedly. FWIW, my ACERT puffs quite a bit out the breather at idle and measured at 2" on the dyno at 79% rated power. Right at the limit. I was not there at the time to watch (truck was 1,000 miles away in San Antonio) and did not entirely trust the dyno results. This due to conversations with the dealer that indicated some carelessness. Anywhoo, 200k miles later it uses no more than a quart or two on a 15k change interval. So don't sweat some blow-by on it's own merit. It's an indicator, not a slam dunk.

 

Seems I was editing while you were posting.

Not a positive discovery (cost and time wise) but does explain some things.

 

Yeah I saw the pictures after I posted the long winded one.

I'd be doing exactly the same. Especially give your mention that the bull gear had been checked and found good, recently.

 

Are you doing the inframe? Are you doing the bull gear? Have you got an estimate yet? Is this a garage you know?

 

DY mentioned it was a referral but left it anonymous. The shop is new to him, but I made the referral. I've been using this shop for the past three years for nearly all truck, trailer, and reefer repairs. I consider them a substantial part of the reason I remain in business today. In fact, I purchased my latest truck from him. It's a 99 Century with a 12.7 that was built right there within the last year. It's been solid for 50k miles so far, and my son isn't gentle with it.