Other day I was headed to a job, got there and pulled in and noticed the truck was missing a little bit and almost sounded like a faint knock, then I saw a bunch of smoke coming from under the hood. It had to of just happened or I would have smelt it going down the road.

Tow it home, compression test reveals 120ish psi on cylinder 5, all the others check out right at where they did a year or two ago..

Pulled the engine today, yanked the head off and here's what I found..







This is one of many pistons that have had a fight or two with a glowplug (previous owner)

Truck regularly sees 12-15psi of boost, I've hit 25 once and 20 another when not paying attention for just a second, head gaskets surprisingly look fine, stock bolts torque per spec to 80ft lbs since I reused them when I did the head gaskets a couple years back.egts stay in check, I think I've hit 1100-1200 maybe five times since I've turbod it. No heat damage anywhere that I can tell.

I'll probably test the injector for the hell of it, but since there's no heat damage and cylinder doesn't looked washed I don't suspect it. Piston was covered in black soot just like the rest..

Now my timing is advanced a bit above stock, but I'm suspecting this piston must have cracked somewhere along the way and just now gave out. Possibly when it had the battle with the glow plug.

Now onto the real problem, I believe this engine has already been bored .040 over, as the measurement I get on my calipers is 4.040, the piston is 4.020, it's not the best quality caliper but thats the measurement I get consistently.

I got this engine used for next to nothing and it was basically as wore out as the engine it replaced. At the times funds were short and I just needed a truck. That was 3+ years ago

I can't find any information on what size the piston is supposed to be, just the bore it goes in...I want to completely confirm how much it's already been punched out.

Cylinder walls have zero crosshatch left, wish I had a bore gauge to see what the taper is, there's also a lip top and bottom that's easily found with a fingernail.

I think the block is either trash, or needs to be sleeved and I have no idea how much that will cost. Last quote I had just for hot tanking and bore was $250, I'll call them Monday and try and get a quote from em.

I'd like to go with custom rings gaps and get rid of the blowby so I can run a road draft tube so when I install my intercooler it can stay clean..

Also would like to head stud it but other than that don't really have much in mind.

Will probably order some cera-kote and ceramic coat the pistons while they are out. The stuff just air cures...$70 for a pint, should easily do all eight. May get the machine shop to take em down a hair to compensate since I'm turbo now..

All the other pistons don't appear to be cracked

Oh, and the first ring gap was .093"

Cylinder previously made 350lbs of compression..

Also want to add the pistons are not mahle, only brandish thing I can find on them is a circled Z, could be junk aftermarkets...

 

If youre using NA pistons get some gapless top rings. Sounds like this engine has been built a couple times, and half assed at that. If you can find pistons, you can bore to .060, or go to 4.110 and use 7.3 std bore. $100 a hole is the usual rate for sleeves.

 

Ouch no Fun

 

Man that sucks! Nobody is ever prepared for these unexpected breakdowns, not that there ever is a good time for them

 

It's just got a ton of miles, with poor maintenance from the po, he told me it had 460,000 on it when he parked it, I was in a bind and took what I could get at the time...I'm assuming the first rebuild was probably so bad a simple .020 or 0.30 over wouldn't do it. 0.06 seems too thin to me, I know the history of this block isn't the best maintenance wise. So id rather not go too thin and chance cavitation.

It's been a good engine to me, even slap wore out it still works daily, this is the first hard failure I've had. Once I get my hands on a bore gauge I'll see what the bore taper is, if it's within spec (highly doubt)

I like these motors, they'll run til you just get tired of dealing with them...

The old motor that came out of it was just flat shot, leaked oil everywhere, had so much blow by if you removed the oil cap it sprayed droplets all over the hood, every bearing in it was copper colored and scored to hell, yet it cranked every day when I needed it and ran until I was done with it.

That motor like this one had zero crosshatch left in the cylinders. But it was a standard bore, sadly I ended up scrapping that block because I thought at the time I'd never need it..

 

Yeah, expected a head gasket to just be blown

I don't think there's ever a good time for a break down to be honest. Luckily I bought my 89 this year so I've got a spare set of wheels and it's standard/4wd so plenty enough to keep working out of til ol red is back on the road. I may just slap a single piston in it and rering/stud..

 

Trust me all engines break down.... except 50 series deeres and 66 series IH

 

Funny enough in the bay next to me is a 50 series Deere engine that's on it's second rebuild with 16k hours on it. It's not abused but regularly worked to its full hp. It had spun three mains...

They ended up just buying a shortblock since the head had recently been done. Think it fetched 8k for the short block..

Machinist was out today so tomorrow I'll see what the damage will be to do it right and may consider less desirable options for now and start building a motor piece by piece if I can find a good block. Iirc they only quoted me around $250 to bore it last time I asked. There's some NOS .20 and .40 over pistons at a reasonable price on eBay so I may go with that if I can find another block.

 

Piston:
Standard Skirt Diameter (measured 90deg to the pin, 1.25" below the bottom ring land) 3.9935-3.9945 (inches)
Standard Piston to Bore Clearance Selective Fit .0055-.0075 (inches)
Standard Piston Rings Diameter 4.00 (inches)
Standard Ring Gap Top Compression .014-.024 Bottom Compression .010-.024 Oil .060-.070

 

Talked to my machinist today, he's moved locations in the last year and does have big enough equipment anymore to bore the block. Recommended me to a different place but they didn't seem very interested in doing it. We'll see what they quote me.

I found a 6.9 for sale with apparently 84k on it, probably 184 or 284 but I may go look at it today. Maybe they'll let me run a compression test on it before I buy it and if it checks out okay I could probably deglaze, rering and go with it instead...

Just got off the phone with the other shop, they quoted me 550 to bore the block, deck it, they knew all about how the Pistons come above deck and will machine them as needed to make everything kosher, line hone the mains, install new cam bearings..and I'm assuming assemble the short block but not sure. That may be a bit more.

He also said he has a three axis machine for the heads that will remove as little as possible...and he can install heavier springs he told me just to buy them before hand and he'll shim them out and also tell me the difference between pressures.

I also got a line on a set of forged 7.3 powerstroke rods for CHEAP, he said they can resize them to fit no problem as well for around 300-350...half of what a set from r&d would cost me..said they do that lots with pulling tractors and he has a supplier for really good wristpin bushings..

Looks like if I can find a block that's not shot it's probably the route I'll take..

 

Found a 6.9 engine that supposedly had 86k miles, I was a bit skeptical but made the three hour round trip and it looked pretty clean...



It was at a junkyard, they supposedly test ran it before pulling it. Didn't want to do a compression test when I got there even though I brought my gauge. Motor comes with a 90 day warranty for free, so he upgraded me to a six month warranty, cash or exchange if they have one.

Brought it home and tested four cylinders, two on each bank, one bank was 340, 345, the other was 375, 355

Tore the driverside head off and this is what I found...







Pistons not only had some battles with glowplugs, but also have significant heat damage....the rear one is flaking...

Also has the factory, unrevised headgaskets, yet the valve train is 87+, valve covers and heads were clean as hell underneath. This is supposed to be an 86 engine but I'm assuming it is an 87...

Appears to be roughly 184k, but rode hard and put up wet. The block is standard bore but no crosshatch left, but for what I paid for it I could sleeve my other motor. Unsure what to think at this point.

Kinda curious if they'd do a partial refund to help cover the machining cost....was kinda hoping for good bores that I could just hone and rering. So much for that idea. Which has got me thinking it will probably be next to impossible to find a block that doesn't need machine work.

Decisions decisions. This is gonna end up being a costly project..

So far I'm around $3500 to have a rebuilt motor with better rods and studs, but other than that stock.

I'll call them tomorrow and see what they say after I get a more solid quote from precision machine, the guy I talked to seemed extremely knowledgeable about these motors and how to do them right. Also said he'd have no problem resizing me rods to fit this block. Said they do lots of tractor pulling engines that are all custom like that.

 

Been following along in your thread.
What is this? the third engine w/o any cross hatch markings?
Your original, the wore out replacement and now this JY engine.
This JY engine may have more mileage than it seems. Going to
be difficult to fine a used engine this many years down the road
in great shape.

JY must have pressure washed it, sure is clean, and amazing
the condition of the Valve Cover, still with the grey paint.

I have read in some threads where the cross hatch was still there
with very high mileage. Wonder if that has anything to do with the
hardness of the steel used when they were cast?

I have that same Banks turbo set up on my 85, The Air Filter is a
K&N and only come from Banks, Ordered it from Summit racing,
but package was from Banks. About $57. The original was tweeked
and bent, don`t see how it did much filtration. I was looking for a paper
filter, but doesn`t seem to be a cross reference.
I need the big Elbo, 3 x 3.5" that goes into the Turbo, not much help
from Banks yet....if ever.

Maybe throw this engine in and run it like the last 2 wore out one`s, and
maybe get 2 - 3 years out of it while you rebuild the other one.
Which ever way you go, I wish you the best.

Charlie

 

My other Banks kit doesn't use that elbow. I wonder if anything plumbing would be right, seems I've seen some drain couplers of similar size/orientation

They cylinders don't look bad, just no cross hatch. I could probably get away with a deglaze honer and new rings, but I'd have to cough up the 400-500 for new pistons...

Still waiting from the machine shop for a proper quote

 

With the shape of these pistons and the compression on this motor being lower than the one I pulled out I definitely would not run it..

 

it's been my experience that NA engines with high mileage show less wear than turbo'ed engines with similar or less mileage .... Just an observation.

probably has a lot to do with how Turbo is driven compared to NA too.