VERY Rough Running

[air-cooled or diesel]

I had my head machined and rebuilt at the same time, but don't remember if he replaced the followers. I know he replaced the guides and valves.

in this post you state you had the head machined? this being a rather general term, could you be more specific? if the head was machined to straighten, or 'flycut', that could be a problem.
you do state surface thickness is at spec, so hopefully that is that.
hopefully the seats are ok, and valves are sealing properly, sounds so,,

eyeballing piston height isn't telling you much, perhaps a dial gauge, sit edge of dial gauge on piston in a 'flat' part and get a reading. this method is fairly rudimentary, but you can get a fairly good idea of your measurements. you could also take something like a basic t-square, and use the measuring part as kind of a flat edge, run over a consistant part of piston and if you have something to measure with you can get a general idea. (if you have a fine tape measure and convert to mm).
the only thing I can think of as far as a variance of piston height would possibly be wrist pin/pin lock. (or possibly bad small-end bushing).
oh yea; I do hope with the valves, you have new springs and stuff.

[StevenPH]

Yea i don't really know the right terms for what they did. 20k ago he cleaned everything, checked for leaks, cracks, etc, and flattened out the head. Replaced valves, guides, springs, and inspected everything else he didn't replace, like the followers and their nubbins.

Just got back from the shop and he cleaned and checked everything. The thickness was virtually precise to the original specs, guessed that the first guy didn't hardly take anything off. Said everything else was spot on, vacuums, valve sealing, other things i didn't understand, and was extremely impressed with the overall condition.

After an hour and half the oil levels in the cylinders are still the same, i'll check back in on them tomorrow.

After that i'll get precise with the piston measurements. I did notice a smell when i pulled the head, but i didn't think much of it. If the heights are off i'll pull the oil pan and see what i can see from underneath.

[StevenPH]

A new discovery: Don't know how i didn't notice this before, but the piston in cylinder #3 is LOWER than it's partner in cylinder #2. about .6mm according to my feather gauge. It seems to be pretty consistent through out the cycle. Piston #3 reaches up to .3mm below the block face at TDC, but #2 is about .3mm above the block face.

Something is obviously wrong here. My next step is to take off the oil pan and take a look from underneath. I'll you all know what i find.

[TylerDurden]

Where do pistons 1 and 4 reach?

[82vdub]

Pull the oil pan plug and see if there's metal particles in the oil. You may have spun a bearing on #3.

[StevenPH]

1 & 4 reach the same as #2, just above the block face about .3mm

[StevenPH]

Just pulled the oil plug - it's magnetic, and totally covered in metal shavings....

think we're onto something here...

[StevenPH]

and we have a winner! The puny little shaving is all that's left of both halves of the #3 bearing.

Now the question of why it shredded itself to death.

Faulty bearing? Faulty install? Maybe timing slipped, crashed the valves into the piston and the bearing lost the battle?

When i did my last ring job i did it in chassis - i was super careful about leaving metal shavings when honing the cylinders (i did the shaving cream method), but maybe something slipped past and found its way into the bearing and slowly tore it apart?

More importantly:

Should i replace all 4 bearings while i'm in there? It seems like i should at least inspect all of them for deterioration, and replace them all while i'm at it.

Should i leave the rings alone and assume they are fine? I'd rather not mess with them unless i have to.

[TylerDurden]

Erk.

Well, I'd certainly check the other bearings. I'd pull #3 piston and inspect the rod, pin and skirt.

I'd replace the valves on #3... they got tagged and could be weakened... dropping a head off one could kill the whole party.

[Prairieview]

You guys are kidding here right??
The crank is undoubtedly damaged. Additionally, every oil passage in this engine is littered with shavings, etc. And he is being told to renew some bearings? Wow.

This engine would have had to have been knocking for some time. And, this was not a clue early on?
I would start trolling for a different engine.

[TylerDurden]

As per the OP, it was sudden onset.

How would shavings get in the oil gallery with 50psi pushing them out into the crankcase for the filter to collect them...?

[82vdub]

You guys are kidding here right??
The crank is undoubtedly damaged. Additionally, every oil passage in this engine is littered with shavings, etc. And he is being told to renew some bearings? Wow.

I agree here. The crank journal #3 is likely worn way past just a simple bearing replacement, and unfortunately, the crank probably needs to be replaced. Depends on how worn journal #3 is, however, with .6mm of piston difference and a bearing that looks like that, there's likely more damage to the journal.

For longevity for a rebuild, I would pull and at a minimum, have a machine shop redo the crank (if it's possible) and pressure wash the block to make sure it's clean and ready to reassemble.

Just curious, when you redid the engine, did you make sure you put the rod cap back on the same rod it came off of, and in the correct orientation? It appears that the sides of the bearing wore, and this could have happened by a cap that wasn't perfectly aligned with the rod it was originally machined for. Did you magnaflux the bearings before final installation or did you use an oversize bearing without having the journal machined for that specific size?

[StevenPH]

Erk is right.

Yes it was sudden onset. I changed the oil only about 100 miles beforehand, and there was no metal on the magnetic plug at that time, for what that's worth. I've had somewhat decreased mileage (maybe 5 to 10 mpg) for about 600 miles, but that also coincides with a move to seattle where i'm driving primarily city driving on hills.

I've ran the engine for maybe a total of a half hour in the 6 weeks since it happened.

When i did the bearings last time i am absolutely sure i didn't rotate them, and they went back with their respective rods. I also measured using the thickness strips per bentley and put in standard size bearings, which my measurements corresponded to.

The crank journal on #3 shows no signs of irregular wear that i can see, but i'm sure there could be some i can't see.


Realizing that the proper course is to pull/inspect/clean the block, inspect and/or replace the crank - that may be something that isn't an option at the moment in terms of time and cost. If instead i do the alternative, (pull and inspect piston #3, inspect the remaining bearings, put in a new set) could i do much more damage than i've done already? Maybe do several oil changes in the first couple hundred miles, and see if i'm getting any more shavings on the plug? Inspect the bearings again after another few thousand miles?

I might not be able to trust the longevity of my job, but on my beater of a VW, that's not really something i've ever had...

[the man 53]

yeah, wow.
Spend the money once and you won't have to do it again prematurely. Everything is probably F'ed down there. Crank, #3 rod out of round, rod bolts...I would not reuse much of anything.

[surfcam]

Crank throws can be fixed as long as they have 1/3 of the metal left. I don't know the economics of it but Goldbar Machine Shop in Edmonton AB can do it so I'm thinking other can too.