Big End Bearing Analysis / Opinions

[f0xy]

Its probably easier if I don't include too much detail on the engine just yet, and see what the general opinion is on the below set of big end bearings are?

They were checked for clearance, and rods checked for roundness when built (ARP rod bolts). Everything within factory tolerances.

The engine has been performing great, making expected power. Its mostly used at full load/wide open throttle and stable oil temperatures around 90-100C in all operating conditions.

The top of the engine is cylinder 1, timing chain end:



Cylinder 2, 3, 4:



Any opinions would be appreciated

[bucksmanuk]

is this a road engine or competition?
How many miles have they seen?
are they a good brand?
how was the clearance checked?
The black mark looks "interesting"

There are some papers around on bearing damage, and I think there’s details on this in Mike Neale’s Tribology Handbook. I’ll have a look when I get home…

[f0xy]

bucksmanuk said:

is this a road engine or competition?
How many miles have they seen?
are they a good brand?
how was the clearance checked?
The black mark looks "interesting"

There are some papers around on bearing damage, and I think there’s details on this in Mike Neale’s Tribology Handbook. I’ll have a look when I get home…

Competition / circuit use only.
No idea on mileage. But id estimate 11-12 events, some being full days, some prolonged high RPM (Spa + Nurburgring).
Mahle brand, standard size.
Rods = Bore Mic. Crank polished and checked with mic. Assembled clearance with plastigauge.
No idea on the marks/wear - Im not nor claim to be a build/assembly/engine expert. Mainly the reason for the post. Crank still looks as it did when polished/assembled 18 months ago. Not re-measured yet.

Like I say the engine had no 'issues' when running. This strip down was only done as the oil pump was being checked.
Its an M54B30 crank (89.6x84mm). 7300rpm limit. ATI Superdamper, 290-300hp.

[stevesingo]

No 1 looks like peak cylinder pressure is occurring too early leading to a failure of oil film thickness.

Does the engine have high compression?

What fuel?

How was the ignition timing determined-Dyno?

[CrutyRammers]

Just an interested observer . But I've not seen those little black "specs" before

[f0xy]

stevesingo said:

No 1 looks like peak cylinder pressure is occurring too early leading to a failure of oil film thickness.

Does the engine have high compression?

What fuel?

How was the ignition timing determined-Dyno?

Standard components and head gasket bar a few head/block skims, and an iron block. 10.2:1 standard, so id imagine a slight amount more if anything.
Yes always mapped on dyno. Standalone management, running wasted spark in three pairs.
This is Alpha-n, ITB, 98/99 RON all the time.

[tapkaJohnD]

2 points:
1/the wear is so patchy, as if there was a vibration causing it. Does the crank have a damper on the nose, and is it working?

2/ Wear is concentrated on the sides of the shells, as if the journals were not grouns parallel to the axis.

John

[f0xy]

tapkaJohnD said:

2 points:
1/the wear is so patchy, as if there was a vibration causing it. Does the crank have a damper on the nose, and is it working?

2/ Wear is concentrated on the sides of the shells, as if the journals were not grouns parallel to the axis.

John

I wouldn't like to see how the bearings looked with the OEM damping pulley - these cranks are known for bad harmonics above the 'stock' RPM limit of 6500rpm. The usual fault is the vibration causing the standard oil pump shaft to snap, or wind off.

The vibration on this particular set up is usually solved by using an aftermarket damping pulley. I run an ATI superdamper for this reason (and a modified oil pump). The flip side is I am spinning it higher than I ever have (7300rpm), which appears it could have having an effect as per your suggestion.

I will pull the crank out and have it checked to be sure on point 2.

[stevieturbo]

And the engine is apart because ?

[f0xy]

stevieturbo said:

And the engine is apart because ?

Engine is out as other work is being done on the car/chassis.
I've made a habit over the years of checking the oil pump sprocket bolt is still torqued to spec if I have the oppertunity to remove the sump (after previous oil pump failure).
From there I decided to check the condition of the big ends after increasing the RPM for the past 18 months.

[Boosted LS1]

tapkaJohnD said:

2 points:
1/the wear is so patchy, as if there was a vibration causing it. Does the crank have a damper on the nose, and is it working?

2/ Wear is concentrated on the sides of the shells, as if the journals were not grouns parallel to the axis.

John

My first thought was that the bores aren't perpendicular to the crank. What do the mains look like? Also, I couldn't see how the rods are being oil fed, am I missing something?

Edited by Boosted LS1 on Wednesday 27th November 20:32

[Boosted LS1]

Boosted LS1 said:

tapkaJohnD said:

2 points:
1/the wear is so patchy, as if there was a vibration causing it. Does the crank have a damper on the nose, and is it working?

2/ Wear is concentrated on the sides of the shells, as if the journals were not grouns parallel to the axis.

John

My first thought was that the bores aren't perpendicular to the crank. What do the mains look like?

Edited by Boosted LS1 on Wednesday 27th November 20:32

[f0xy]

Boosted LS1 said:

My first thought was that the bores aren't perpendicular to the crank. What do the mains look like? Also, I couldn't see how the rods are being oil fed, am I missing something?

Edited by Boosted LS1 on Wednesday 27th November 20:32

I will have a look at the mains in the coming days. Quite a bit more needs stripping to get the crank out the block, so that will be the next plan I think.
Assuming you mean the rod bearings? They are fed from the crank journal

[Boosted LS1]

f0xy said:

I will have a look at the mains in the coming days. Quite a bit more needs stripping to get the crank out the block, so that will be the next plan I think.
Assuming you mean the rod bearings? They are fed from the crank journal

I realised that, was having a thick moment, lol.

[f0xy]

Boosted LS1 said:

I realised that, was having a thick moment, lol.

Ah, seen your edit now!

Going back to your suggestion, how would that occour?
The block has been honed twice previously, but surely not enough material is removed to skew the bore in that process, considering im still running standard ring gaps. The other variable is a bad crank position?

[stevieturbo]

They're standard soft bearings. You dont seem to suggest anywhere there were any signs of a problem.

It seems you're worrying over very little here. The bearings may not be perfect, the crank may be moving a little in some regard....but I've seen a hell of a lot worse....and been running perfectly.

[f0xy]

stevieturbo said:

They're standard soft bearings. You dont seem to suggest anywhere there were any signs of a problem.

It seems you're worrying over very little here. The bearings may not be perfect, the crank may be moving a little in some regard....but I've seen a hell of a lot worse....and been running perfectly.

Its more curiosity than worry to be honest. Interested in learning what COULD cause it.

[Evoluzione]

There is little chance of seeing much from those pics, they're no good for bearing analysis. All I can see is the shiny bits and they're normal.

[Boosted LS1]

f0xy said:

Boosted LS1 said:

I realised that, was having a thick moment, lol.

Ah, seen your edit now!

Going back to your suggestion, how would that occour?
The block has been honed twice previously, but surely not enough material is removed to skew the bore in that process, considering im still running standard ring gaps. The other variable is a bad crank position?

The crank line boring may not be perfect or there might vibration at the rear of the crank, gearbox? If there is an issue I'd expect the main shells to show something.

[99hjhm]

Just pretty normal wear from track use, some scoring from dirty assembly or similar. Cant tell what the black mark is though.