Detroit 60 series 12.7 big block

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Dpeterson3530, Apr 2, 2020.

  1. Dpeterson3530

    Dpeterson3530 Bobtail Member

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    Hello,
    I am completely new to trucking and this forum but have searched for awhile and can't quite find a good answer. This is my first truck ever.
    I just purchased a 1994 international 9400 with a Detroit 60 series 12.7l big block engine. I got a hell of a deal, I believe the motor is worth more than what I paid for the truck. I've already been offered 25% more than I paid for it. The previous owner has owned it for roughly 10 years and I don't think he has touched the motor or done any real maintenance on it. He's fixed parts on the actual truck but nothing with the motor. The truck has 800,000 miles and has mostly been used for a custom harvest/farm truck the last 10 years, putting on roughly 10-15,000 miles a year so those are hard miles but not many. Thats exactly what I will be using it for.

    My question is, what should I get checked on this motor, it is due for an oil change and my uncle is highly recommending that I have them drop the oil pan and check the rods and mains and the bearings on the lower end. I have talked to muiltiple people and looked online and cannot get a solid answer. Is this something worth doing? Also are there any other things that should be checked ASAP? I really need to just keep it from blowing up for the next 3-5 years and it will pay for itself ten fold. I will be getting an oil analysis done for sure every year. Any help or insight you guys can provide would be awesome. I am young, 23 years old and when I go into the truck stores in my area they brush me off and act like they don't want to help or that I am a nuisance or they don't know what I am asking because I don't know the proper terms. Thank you in advance!
     
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  2. Deere hunter

    Deere hunter Heavy Load Member

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    Rods and mains will go way over a million if oil changes have been maintained! I would change all fluids in truck trans and rearends.
     
  3. Rideandrepair

    Rideandrepair Road Train Member

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    Rods and mains typically don’t wear much, even at 1 mil miles. The weak points on your motor are wrist pins, and pistons. They would sometimes come apart at about 750 k, later blocks added oil squirters, and different piston designs. I don’t think anything can be done about block not being already drilled for squirters, (may1998 and newer). However you may be able to upgrade to drilled piston rods, and newer style pistons when you are ready to overhaul. A lot of research will be needed, to ensure everything will work. Dealers won’t help you, only supply the basic parts based on serial #. They were still dependable, seems if they made it past 750, they stayed together. Just my opinion, no facts or numbers to back that up. But at 800k, you have evidence of its reliability. Problem is when wristpins come apart, 50% time they’ll knock a hole in block. Depending on the stroke when it fails. It’s common enough, that I knew of one Guy that had both his Trucks do it within a few weeks of one another right at 750-775k. One ruined the block, other didn’t. I would run it, and take my chances. Blow by is a common problem on all 12.7s. But again it will still run and pull good, even with bad rings and cylinders, till it starts pushing water or mixing fluids. Then it’s time to overhaul it. Aftermarket kits from Mahle or FP are very good, if not better, and cheaper than original Detroit kits. The other weak point is the bull gear. $900 part, $2000 labor. If it goes out and strips other gears, bends valves, post failure cost can easily be double that amount. Detroit recommends changing at 750k. Though most change them at 1 mil or so, when getting Overhaul done. I recently changed my original one at roughly 2.2 mil miles, it was still good. Again I would take my chances on that. You can remove access cover and use a prybar to check the bearing on it. All said, take advantage of the great deal you got, run it till you decide it needs an overhaul. No sense in throwing money away, They usually run like a timex, just keep ticking. Meanwhile you can research the 12.7s even find another 98 or 99 block, build one, the way you want. Or do an inframe, with head and injectors on yours for around $8000 or less in parts$12,000 with labor. $15000 with new bull gear and added labor. Maybe less, if you buy the parts right and get the right mechanic.
     
    Last edited: Apr 2, 2020
  4. pavrom

    pavrom Road Train Member

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    I am completely new to trucking ...
    I got hell of a deal ..
    Those say pretty much .....:)
     
  5. Rideandrepair

    Rideandrepair Road Train Member

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    Gotta love it, jumping in with both feet. Best way to learn. Too much info can be discouraging sometimes. I like a challenge. Got my CDL, without going to school, no Megas involved, Bought Truck, eventually got Authority. Bought houses,Trucks with minimal or 0 down, His many times have I heard,” you can’t do that”? Lol. Answer “ Oh yes I can! Usually I can’t really means I won’t. Lol
     
  6. jamespmack

    jamespmack Road Train Member

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    Replace bull gear bearings 100%.

    If you remove bearing to check, just replace them. You enter to much dirt by just checking them. Or get oil sample and run them. Chances they are fine.

    94 didnt normally have piston problems. But dont run extended oil changes. 10-12k max.

    Might wanna pop valve cover, check rocker arm tips. If it has the old style clips I would up date them and check cam lobes. If rocker shafts are worn just flip them 180° In same location.

    Check DCA in green coolant or maybe just drain, flush and fill with red extended life.


    Any fabric fuel line over 7 years old replace.
     
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  7. Rideandrepair

    Rideandrepair Road Train Member

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    Never heard of flipping rockers, Maybe I should do that to mine. Fresh overhaul, kept rockers, original over 2 mil. Thought maybe replace them in future, maybe just flip them?
     
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  8. Dpeterson3530

    Dpeterson3530 Bobtail Member

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    Thank you all, I will continue my research I really appreciate the advice they wanted like $1,000 for an oil change and to check the lower end that's not including the $300 bearing kit replacement. I would like to spend a little bit to make sure it will make it this year because it's my first year custom harvesting on my own then I will have a little more money to play with for repairs.
     
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  9. Dpeterson3530

    Dpeterson3530 Bobtail Member

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    He put a new rear end in about 2.5 years ago and also put a new radiator about 4-5 years ago so rear end fluid and coolant should be ok I believe. but will look into changing the trans fluid. Thank you
     
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