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post #1 of 19 Old 03-12-2013 Thread Starter
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defining "rebuilt"

What constitutes an engine as being "rebuilt?" Looking now at an `85 with a rebuilt Perkins 4-108, and just wondering what should be involved - as in, what should I look for, look for, or ask about?
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post #2 of 19 Old 03-13-2013
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Re: defining "rebuilt"

Actually, I think that yours is a particularly astute question. What constitutes a "rebuilt" engine?

I think that you have to ask as to what was re-built. It may help a bit to know about engine terminology but if you do not ask you wont know if they just replaced the water pump, alternator, gave it a paint job and called it "rebuilt". Was there a mechanic involved? Is there a detailed work order? If not and even if so, what was done?

Where the main shaft bearings replaced?
New head or manifold?
Transmission?
Rocker arms?
Valves?
Cams?
Injectors?
Fuel pump(s) and fuel tank?

In some ways a "rebuilt" engine is a neat way of saying that: "we did something fairly major to the engine" without saying what exactly was done and who did the work.

My $.02

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Last edited by CalebD; 03-13-2013 at 12:52 AM.
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post #3 of 19 Old 03-13-2013
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Re: defining "rebuilt"

I'm about 75% done rebuilding my 4.108 -- here are a few thoughts specific to that engine.

You need to ask the owner about the engine. If he did the rebuild himself, he should be intimately familiar with the engine; if he had someone else do it, then go talk to that person.

o Ask for documentation of the rebuild. There should be a lot more than just a receipt for an aftermarket rebuild kit.

o At a minimum, here's what should have been done using parts from a rebuild kit. Some of this can be done in a DIYer's garage, but some of it definitely needs to be done in a machine shop.
- Cylnder liners replaced and honed.
- Crankshaft polished.
- New pistons.
- New valves and valve guides; valve seats ground (not just lapped).
- New main, big and small end bearings.
- All new gaskets.
++ Red flags:
- Reground crankshaft. The Perkins cranks are hardened using a nitriding process that only penetrates a very shallow way into the crank. If the crank was reground, much (or all ) of that hardening was likely removed.

o The aftermarket rebuild kits lack a couple of things that also need to be checked:

- Oil pump. This is the only mechanical part of your engine that runs using unfiltered oil as a lubricant -- they tend to wear faster that other parts of the engine. Verify that the pump was either replaced or checked to ensure it was still within factory specs.

- Rocker arms and shaft. I found significant wear on the shaft. I sent the entire rocker arm assembly out for rebuild (new shaft, new bushings, arm geometry reground.)

- Fresh water cooling pump. Mine was leaking. Rebuild kits are no longer available. The only fix is a new pump.

- Raw water cooling pump. Also should have been torn down and rebuilt (new bearings and seals.)

- Fuel delivery components. The lift pump should have been disassembled and checked. At a minimum, the injectors should have been pop tested (better yet rebuilt using new nozzles.) The injector pump should have been thoroughly checked and seals probably replaced.

If you are interested, here's the thread that I'm using to document my rebuild (link)
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post #4 of 19 Old 03-13-2013
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Re: defining "rebuilt"

Quote:
Originally Posted by PorFin View Post
I'm about 75% done rebuilding my 4.108 -- here are a few thoughts specific to that engine..........
There you have it... from one who knows. Be sure to check out that thread too. Thanks PorF...

Ron

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post #5 of 19 Old 03-16-2013
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Re: defining "rebuilt"

When rebuilding an diesel, is line honing done and bigger bearings done as they are in gasoline engines?

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post #6 of 19 Old 03-16-2013
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Re: defining "rebuilt"

As others have said, there is no definition of rebuilt. Buyer beware.

Unless truly taken down to the bones and everything replaced with new, what do you really have? You have a motor with whatever hours on it that has been repaired and presumably runs well. No guarantees.


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post #7 of 19 Old 03-16-2013
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Re: defining "rebuilt"

Folks seem to often sell right after a rebuild which makes me think they lack confidence in the quality durability of what they've done. I'd actually want it to have some run time. In discussing their work I'd be listening for tell tale signs of competence. Torque wrench, loctite, photographs, micrometer measurements, new parts even where old ones may have some life in them such as a water pump or alternator. Short cuts less likely if they thought they were going to keep her. Amazing how many people advertise they've freshened or "redone" their motor. I doubt anyone doing a professional job will lack receipts or photos documenting just how much was "redone". To me lacking the depth of knowledge to discuss particulars would be a red flag. Good luck. There ARE competent and honest folks out there.
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post #8 of 19 Old 03-16-2013 Thread Starter
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Re: defining "rebuilt"

Good luck. There ARE competent and honest folks out there.

Do any of those folks live and sell boats in FL?

Does the engine ususally get removed from the boat for a "re-build?" Seems like it would need to based on everyone's responses. The pics of the boat's engine don't show many shiney/new parts..
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Re: defining "rebuilt"

Quote:
Originally Posted by cparclan View Post
Good luck. There ARE competent and honest folks out there.

Do any of those folks live and sell boats in FL?
Nobody knows where this elusive creature lives. It's only been seen in grainy photos at great distances.

Quote:
Does the engine ususally get removed from the boat for a "re-build?" Seems like it would need to based on everyone's responses. The pics of the boat's engine don't show many shiney/new parts..
Yes, it must be removed to fully re-build, but a lot of big things could be done with it in the boat. If you don't see a brand spanking new paint job, I would be sure it wasn't recently "re-built". Then I would probably run from it, as the owner seems to have a disability with the truth. I get like that.


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post #10 of 19 Old 03-16-2013
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Re: defining "rebuilt"

Quote:
Originally Posted by Minnewaska View Post

Yes, it must be removed to fully re-build, but a lot of big things could be done with it in the boat. If you don't see a brand spanking new paint job, I would be sure it wasn't recently "re-built". Then I would probably run from it, as the owner seems to have a disability with the truth. I get like that.
Have a real good look at that "shiny new paint job" too to try to ensure that it wasn't ONLY painted up shiny just to dress it up...
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