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Discussion Starter #1 (Edited)
I have a 4BT with about 180K that I am going to throw into this land cruiser I am building. The engine is out now, mostly clean now also, and in need of complete regasketing including the head gasket (which leaks oil & coolant out the side) but the motor itself runs great and is actually super powerful. It might have slightly low compression but if it does, it is minimal would be my guess. I put over 1000 miles on the bread truck before the rebuild, as I said ran great. Havn't done a compression test yet but plan to, but need to replace the head gasket regardless...

Cummins complete gasket kit is about $600.. Rebuild kit about $700 or $800 if I remember correctly, using OEM. There are some cheap aftermarket rebuild kits that are name brand as low as $500 shipped. I would probably not consider one of these for the piston parts etc, most likely, except unless I choose to not rebuild and only use the kit for the gaskets, as its cheaper than OEM and gaskets are not as important. I would probably need to buy a second Cummins headgaket regardless as Cummins recommends you use a thicker headgasket to replace any metal removed in the head milling process. And they only sell the thicker gaskets separately and they are $50 each so not that bad.

Question is, I haver never rebuilt an engine before. I have good technical knowledge and ability and now think I would probably be fine.. But seating the pistons right, the measurements etc that are needed to do this (correct??) - or do you simply bolt all the new stuff together on the crank, use thread locker and torque wrench and you are good to go with a diesel? Any feeler gauges/precision measurements that I will have to do that requires "special knowledge?"

I was reading this thread about good techniques to get the pistons to seat right. This is on V8 gassers but I feel that its probably the same basic thing for diesels...? Here is the link:
http://www.circletrack.com/howto/4639_maximum_power_piston_rings/
( <-- Good reading I feel like regardless )

I have no problem doing everything mentioned in the article except it is a little confusing for me using the feeler gauges, etc. And the piston leveling tool, bot can probably figure it out? But I do have the big thick 600+ pages Cummins manual that I think goes though all this?

RE machining, here is the ala carte menu for machining from my favorite machining shop that is very competent and well known & respected...
$65 head milling
$220 head milling and valve grind (probably required is my guess)
$60 cylinder honing
$90 block deck mill
$125 cyl boring including honing
$125 crank grind...

Here's a cost breakdown of what it will cost according to requirements:
- Head milling alone, best case scenario, $65.
- Head + valves, head gasket job only, $220

Machining if rebuild the motor:
- If everything OK valve wise (probably doubtful) + cyl wise, head + deck mill, cyl honing: $215
- Valve job needed, head + deck mill, honing. $370
- There is some scarring in the cyls, $450
- Scarring in cyls, need a crank grind too.. $575

All this, plus parts (+ tax)...

So far, this whole truck has been an expensive build, pretty much everything on the truck is new or rebuilt, truck is/will be entirely restored, but problem is I am running out of money and am fairly poor right now, literally every spare cent right now is going to it, I have probably about 70-80% of the stuff bought already now and almost all big ticket items paid for already. If I tore this stuff apart, at this point hate to say, but it would probably take a few months to get the $$ to put everything back together...

Also, I am a little "scared" I supposed because I havn't ever rebuilt a motor before. Also I am wondering if I should do all this too because the engine runs well so far...

I guess I should wait an see what the compression test says? Anyone have any advice on rebuilding techniques or is it relatively easy you think? I have done all sorts of crazy machanic jobs, probably over 6 headgasket jobs, timing belt/gear jobs, including on several fancy fuel injected cars and other diesels. Never rebuilt a transmission myself but am a pretty capable, smart, and patient/cautious mechanic.. I can also probably dig up a friend or two who has decent engine rebuilding experience to maybe help me out probably, I would have to bribe them with something, but probably worth it..

I talked to a local diesel engine rebuilder/specialist, and he said "180K on a B series - nothing at all, I wouldn't rebuild it, replace the head gasket, do the cheap gasket kit, and call it quits." Then I'd be in it probably less than $700 which I could do a lot easier than $1500 or so I think at this point..

Then I am also weary as engine runs great now, what if I did all this and the pistons didn't seat right or something like that.. Of course I will take every step to break in engine correctly, but sure would be a bummer if I went to all this time + expense for nothing, when engine ran great before... But that said, I like the idea of a fresh rebuild to match the rest of the car...

Thoughts / comments?
 

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My thoughts.
1. Do a compression test.Go from there.
2. If ok, get the head checked ,just to make sure it's not cracked. If ok ,then just do a head gasket and reseal the engine and run it,if it has the power and starts good.
3. have fun,and take your time.

4. Engine rebuild,these engine are easy to rebuild,just takes time and a clean place to rebuild,the machine work it takes a good machine shop to make a engine last ,all it takes is a small mess up and the engine won't last.The cam bearings are a big killer if they don't do it right or just off set a hole just by a little no oil pressure or low .

Thanks
Scott
 

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How much blow by does it have after warmed up?

That dude in the link sure is "Hen Peckin'" those rings to death. LOL :smile:
 

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I have rebuilt a few engines (all gassers) and my cousin is a diesel mechanic instructor for Deere, so don’t take this as law, JMHO:

A rough way of telling if a rebuild is warranted is to drag your fingernail up or down the cylinder wall, if it hangs up at points above or below the ring travel area; then perhaps a rebuild is a good idea.

If there is a lip on the cylinder wall you may be able to ream it out and go with a simple hone, if your cylinders are within spec. You need some bore gages and a micrometer to measure it right. If you know an engine rebuilder they could help you out, it won’t take long.

Specs are in the B series shop manual. Only if out of spec, then do you need machine work. Same goes for the crank, if within spec no need to machine.

If not a total rebuild I would strongly recommend replacing the main and rod bearings they are relatively cheap and easy while you have it apart. In addition I think replacing the thrust bearing (#4) by itself is not quite as effective in extending life of the engine as replacing all mains at once.

I have no idea how many miles were on my engine. I just broke down my 4BT and I do have a little glazing but the cross-hatching is still apparent, and no ridges in the cylinder walls. I plan on replacing all the gaskets, throwing a set of main and rod bearings in it and going with it. Should last 500,000 miles…

…I think.
 

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What can you live with?

Personally, I like things sealed up but if they're running good and oil pressure, blowby, etc is ok, LEAVE IT.

On the other hand, if you've got the time/money (and these are big issues here too... still have my 6bt sitting in the garage and NOT in the truck!!), REBUILD IT. You'll have piece of mind and feel better about the whole project. Otherwise, you'll be looking at your nice new truck and thinking about the motor.

EDIT: oh yeah, what's the name of your machine shop? I need some work done on a 454.
 

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It all sounds good to me, compression check while the engine is together, make sure the head is not cracked, Measure for excessive wear in the cyl if you have the gages if not give them a real close visual( I wouldnt even pull the pistons if the walls look good). New bottom end bearings and it will run forever. I have put together some pretty loose engines in the past out of necessity, they ran strong for a long time.
Carl
 

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Do a cylinder leak down test while you are at it.
 

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Discussion Starter #8
cool thanks for all the advice guys.. I posted this up on TDR too, most people are saying the same thing over there. But also makes me think maybe I can dig up a diesel guy somewhere who can show me how to rebuild it maybe.. But I guess thats it I decide to do it I suppose.. Anyway, I spent some time with it tonight, good news is I think I figured out all the belt routing with the AC compressor.. As soon as I get the compression tester I'll post up the #'s...!

Here's the TDR thread...
http://www.turbodieselregister.com/forums/showthread.php?p=1696367#post1696367
 

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There's some good advice here but I see it somewhat differently. These and other internal combustion engines are a heat pump. The number one factor in power production is cylinder/ring sealing. The next two items are headflow and camshaft profile. I don't think the Cummins B series need a cam swap until you get off-the-dial crazy on HP production.

Having said that, I can't see taking apart the head/oilpan/block/bearings and not attending to the cylinders and rings. Doesn't take much to properly crosshatch hone the cylinders, after checking for shape, and then properly end-gap a set of rings and install [after thoroughly cleaning ring lands] while you're at it. After honing it's very important to thoroughly clean the block. That includes scrubbing the bores with HOT soapy water and a stiff bristled brush and then rinsing thoroughly with HOT water, 3-5 times. Dry with lint-free rags and lightly oil cylinder bores and bag it while you work on other stuff.

While the head is off there's no better time to do a quick gasket-match porting job on the head. It's pretty easy and cheap overall and adds a lot to your basic power platform. That price for a valve job and head resurface sounded pretty good to me, if they really do quality work.

With block, head, rings, bearings, porting and all done you would have a very long distance engine that you could be absolutely sure of and a solid platform to build off of. Seems like the best idea for happiness tomorrow.....?
 

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