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[BoostedSchemes]

First off, I am probably picking up a spare bottom end with stenzletim this weekend so this is a moot point...

I took the head off my turbo bmw today to find that the stock HG survived 30psi for 6months but the bottom end suffered... the pistons all look charbroiled, worse than some 300k+ hondas I've stripped... and on a few pistons there is slightly more gap on one side of the bore then the other... this means ring is gone or what?
On one piston there is clearly a litttttttle sliver missing from the side.

My diagnosis is extended use under lean condition + aggresive timing chewed the edges off the pistons = all the compression during combustion leaks into the crankcase which cause my massive oil burn.

There is probably nothing to do short of a complete rebuild but I would like to get out of this as cheaply as possible... any suggestions/opinions?
I was considering just swapping the visibly damaged piston which had 0 comp, but what if I just replace the rings on it? I dont intend to do any machine work regardless of what I do. I know I may sound retarded but its because I'm retarded.

[Atticus]

pics 

you have any way of measuring the oval and taper of the cylinder?

[Adam Hopkins]

Honestly, All of your pistons saw the same amount of damage as the 0 comp one. Could be cracked ring lands?I have rebuilt motors 1 slug at a time and had some luck. Then again I have just replaced just one piston just to have another one shit the bed 2 dyno pulls later.

If it were me and I was in the same situation I would do it correctly the first time.

[Tim]

Your rings tried to contain the detonation that was hammering the tops of your pistons, they got hammered too.

Aluminum is pretty soft shit so imagine what your ring lands look like on the 'good' pistons being that some of your pistons the ring lands eroded as much as they did.  They get hammered directly from the detonation and also from the reaction of the rings from that detonation.

Then think about the missing aluminum, where did it go just vanish?  the rest of your oil system has aluminum rubble in it.  I can probably dig up pics from my first ls with broken pistons, I just ran some kerosene through it and slapped some replacement slugs in it ghetto style anyway.

Then think of the detonation hammering on the top of your piston to do all that shit, where did that force go?  It got translated through your rod and bearing to the thin film of oil that was supposed to keep the bearing from meeting the crank.  It didn't and right now your top bearing on all your rods will be sloppier and different color from repeated slight contact with the crank during detonation.  Sure they seem to work fine for now, but reference the earlier mentioned ls and I'll tell you it only lasted a few thousand beaten miles before it spun a rod bearing, now the crank and at least one rod is shot.  Cost of future rebuild just jumped agian.



Get this new block and clean the fuck out of your head, oil lines, turbo, anything reused that sees oil pretty much.  Then take your old block and forget about it for a while till you have a couple bucks or find more cheap parts.  Replace a minimum of bearings, pistons and rings, and at least give it a hone.  But a machine shop to check the bores and a basic hone is really not much money.  Then you'll have a spare block that may have a fighting chance at doing more than just waisting your time.

[BoostedSchemes]

I did beat it for another 2-3 thousand miles after losing a couple cylinders... You're right Tim. 

[Tim]

if you're short on space I have access to a massive barn we can store parts in until you're ready to build.  I didn't clean enough space to pull anymore complete cars in but a few engines will fit just fine.

[BoostedSchemes]

I remember the last time I stored a motor at someones place 

But I doubt I have a choice and your about 99999x more trustworthy even if your not there to hawk over it all day.

[Tim]

I remember the last time I stored a motor at someones place 

But I doubt I have a choice and your about 99999x more trustworthy even if your not there to hawk over it all day.

ooh forgot about that one.  I was all set to buy that fucker too.

I let a guy take an engine to his automotive tech sort of trade school cause his teacher wanted to teach about rotaries.  They would give me the housings for porting before reassembly since that was my plan for the engine, and all I had to pay for was the new gaskets since they didn't get any freebies for the rotaries.

found out the next week the kid was a junkie and was kicked out of school a month earlier.