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PostPosted: Wed Aug 13, 2014 1:13 am 
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Location: drinking devil fuel
Car Model: ST205
I can't see how you get det damage on 2 of 4 cylinders easily though. It would have to be fuel related

I keep coming back to oil flow issues in the crank or oval crank journals. Correct stock clearances will only not knock it the oil film is intact

If it's endfloat related there will be witness marks - remember your scrap block with the milled #3 main web and cap Chris


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PostPosted: Wed Aug 13, 2014 9:38 am 
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Here is an album with some pictures of the old conrod bearings I removed not long after I bought the car. The top halves on every pair are the more worn ones. There is 1 which looks worse than the others, I don't know which bearing is from which rod unfortunately, but I feel like the bad one is from either 1 or 2.
There is a picture of all 4, and there is 2 pictures of each bearing, one top down and one from the side. Sorry about the reflection it's hard to get the light right. I don't believe I measured the clearance on these before replacing them, I just looked at them and decided they were obviously fubar so replaced them all.
http://imgur.com/a/ZNYVW#8

I'm thinking that I'll buy new thrust washers and conrod bearings today, but I'm not going to do the mains, because they are not showing any signs of strange wear, they are in spec and look nice and even throughout to me.

I pushed a pin up through the oil holes in the rods to make sure they are not blocked, they didn't appear to be. I was thinking if there is a flow issue, wouldn't it be affecting the bottom halve of the bearing too.... because there is just one oil supply hole in the crank on each journal, this would supply the whole bearing as it rotates?
By the way, my oil pressure was good before I disassembled, 18-20psi once warm on idle ( up at 80psi nearly cold start ).

Here's a picture of the bottom of main bearing #3 ( and a close-up )

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They all looked like that, same with the top halves. The top halves also have the groove for the oil, so they are in the right way at least.


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PostPosted: Wed Aug 13, 2014 9:50 am 
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By the way, looking at the newer bearings that I've removed on 1 & 2 it looks to me like either:

OVERLOADING or CAVITATION from the pictures in here: http://www.nb-cofrisa.com/docs/web_fallos_ing.PDF
I'm leaning more towards overloading to be honest, it's probably running excessive advance on the SARD ECU. Make sense? Probably detting it's *bleep* off.


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PostPosted: Wed Aug 13, 2014 12:22 pm 
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Joined: Sat Sep 02, 2006 3:13 pm
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Location: Bournemouth
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two_OH_five wrote:
I can't see how you get det damage on 2 of 4 cylinders easily though. It would have to be fuel related

I keep coming back to oil flow issues in the crank or oval crank journals. Correct stock clearances will only not knock it the oil film is intact

If it's endfloat related there will be witness marks - remember your scrap block with the milled #3 main web and cap Chris


I agree, hence why I suggested checking ovality, big end endfloat and crank endfloat.
It's important to actually measure the clearance / endfloat rather than just thrust washer thickness as the crank or block could be worn if there was a previous thrust washer failure. I've known 2 of these failures now, one in the MR2 and the other in the black 205 I bought. I suspect previous owners riding the clutch causing rapid thrust washer wear.

Reading & thinking about it more, I'm thinking the clearance on the sides of the rod help to hold the oil in the bearing rather than letting it pour out of the sides easily.

Those original shells don't look too bad, better than the new ones in fact. I certainly wouldn't expect them to be causing big end knock without some other issue. It's possible the previous owner had a failure of some sort and stuck a new set of shells in & sold quick.

One thing is for sure with engines, taking short cuts usually ends in tears. I suspect that a new set of bearings will fail in slightly less time than the previous set. It's important to take the measurements to make sure all is within spec. Also be sure to chect the correct grooved main bearing shells were used in the block side as this would also cause oil starvation to big ends.

Also when putting it back together cleanliness is important. Wipe all parts with clean lint free cloth immediately before fitting, particularly all bearing and bearing carrier faces. Make sure you put plenty of lube on bearing shell faces and crank journals. Keep time to a minimum between cleaning & refitting as all the time it's exposed it's collecting dust. This is why engine building is best done in a clean room. Interesting to note that by far the most common reason for premature bearing failure is dirt / contamination.

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