Has anyone ever seen wear like this on rod bearings? These are from the cap end of rods 2-4 from a FWD 1.8L Mazda BP N/A and are in order and orientation as removed. #1 spun 2 laps into a track day sending me home early. This engine has 45 hours on it and has competed in 4 races and a fair amount of dyno time. What happened?
Were the rods resized before it was put together? Seems like they are out of round or deformed during the torquing process.
Oil starvation most likely. Poor drainback causing aeration? Or high G's moving oil away from the pickup?
Windage tray? Oil scraper? Trap doors and high capacity oil pan?
Same comment as above but will add what was the bearing clearance? Was the crank checked for roundness?
Cap end pinching like that usually means excessive revs with too-flimsy rods.
When it gets really bad (or the rod bearings don't have enough out of round at the parting line) the edge digs into the crank, wipes the oil film off, and you get what I assume happened at #1.
The curious thing is that it happened after one can assume the engine has proved itself. Did you ever do oil filter cuts before this happened? What do the main bearings look like?
Thank you all for the replies.
minivan_racer wrote: Were the rods resized before it was put together? Seems like they are out of round or deformed during the torquing process.
Clearance was checked with plastigauge across the profile of the journal only.
bentwrench wrote: Oil starvation most likely. Poor drainback causing aeration? Or high G's moving oil away from the pickup? Windage tray? Oil scraper? Trap doors and high capacity oil pan?
Never had oil starvation in the past 25k miles that this car has been on track. I did just add a crank scraper, however.
jimbbski wrote: Same comment as above but will add what was the bearing clearance? Was the crank checked for roundness?
The crank was polished and checked at a machine shop before assembly.
Knurled wrote: Cap end pinching like that usually means excessive revs with too-flimsy rods. When it gets really bad (or the rod bearings don't have enough out of round at the parting line) the edge digs into the crank, wipes the oil film off, and you get what I assume happened at #1. The curious thing is that it happened after one can assume the engine has proved itself. Did you ever do oil filter cuts before this happened? What do the main bearings look like?
These are forged h-beam rods that are for all intents and purposes overkill for this application. Main bearings look fine. Never cut the filter between events, but the drained oil was always clean.
All the crank has to do is to touch the soft bearing material and disaster shortly follows. The soft material tears and balls up and smears and gets only worse until what you see.
Are there any fret marks on the back side of the shells?
What was side clearance?
Where are head drain holes? If the holes are in the center sustained lateral G's will not allow the head to drain. (BTDT)
kcbhiw wrote: These are forged h-beam rods that are for all intents and purposes overkill for this application. Main bearings look fine. Never cut the filter between events, but the drained oil was always clean.
What brand? Saw this come up today on Speedtalk. Aftermarket forged doesn't necessarily mean "good", it just means aftermarket and forged.
I would suggest measuring with micrometers rather than plastigauge. Assemble the rods with the bearings in place and measure the ID. Then measure the crank journal OD. That is the only sure way I know to determine clearance. I never use plastigauge.
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