Spun big end bearing - Rover V8

[debaron]

Just been informed my engine has spun a big end bearing (journal 8). Was less than 100 miles old. Obviously gutted.

Built it myself but was the 4th one I've done so not a novice. Advised it looks like oil starvation or picked up some debris.

Anyone with a keener eye let me know if they agree/disagree?

Oil pressure warning light was not seen at any point

[debaron]

Max_Torque said:

You also need to take the crank out, look for any signs of oil starvation in the mains, and check the oil feeds are clear. You might also want to check the big end for circularity, nip, and the rod for straightness. For a bearing to spin the cause is either:

1) lack of lubrication
2) Damage from debris
3) misalignment leading to uneven loading

Excellent advice thankyou.

Crank is still in the car so will check feeds as soon as I can.

Can a bent rod cause a big end bearing to spin?

[debaron]

gottans said:

I would look at the main bearing to big end oilway in the crank as the other big end on that journal looks fine, is the other big end fed from the common main bearing oil feed okay? If not then may be the oil feed to the main bearing is the issue.

Thanks Gottans, sound advice. Tried checking this today but crank needs to come out for proper inspection.

[debaron]

stevieturbo said:

More importantly what work as done 100 miles ago, by who and why ?

One way or another there has been a lack of oil there.

You ask about a bent rod causing it....why would you be asking about a bent rod on a 100mile old engine ?

Stevie:

Used 4.6 engine converted to 4.8 - new forged pistons - custom top hat liners, original rods shot peened and polished. No sign of bending. Checked by Rob Walker - BUT the used 4.6 engine did show signs of water leaking behind one liner (number 6) so could have hyrdo-locked in it's past I am guessing? Rods did not necessarily go back in same order but were independently balanced.

[debaron]

PeterBurgess said:

Did Rob measure the big ends of the rod to check for ovality and one to another?
Peter

Hi Peter,

I'll need to check with Rob - will call him tomorrow.

[debaron]

stevieturbo said:

and how is this capacity increase achieved ?

give full details, lack of information is useful to no-one.

And are you saying you used a block with known water issues, without rectifying them ? And that you used old rods, without checking them too ?

Stevie: It's 96mm bore rather than 94 with 3 thou clearance betwixt forged piston and bore so custom top hat liners must be used. Machining was done by Dom at Power, who of course is familiar with this.

Water ingress issues are well known with standard liners on RV8 and as I have always understood, top hat liners are the ultimate solution and in my opinion was therefore 'rectified'. The water ingress on the original liner did not look serious enough to cause a hydrolock, and infact to my untrained eye may have even been something else entirely. I'm sure you can understand it's hard to tell on a dry disassembled engine. I suspected water ingress mostly because the crosshatch marks on the bore were much less visible than other cylinders and the cylinder looked a bit cleaner than the rest IYSWIM.

Rods were indeed the standard 4.6 rods from said block - I'll need to find out exactly what was checked on the rods tomorrow.

Incidentally forged rods from Arrow were above the £2000 mark so were a non starter at this cost.

Engine was to be used for light supercharging at some point in the future.

HTH

Edited by debaron on Thursday 30th August 22:20

[debaron]

Mignon said:

Also detonation, physical contact between the piston crown and cylinder head, incorrect bearing clearance at assembly, big end bolt coming loose. Far too many possible causes to be worth guessing at.

Detonation is possible... but with forged pistons while being tuned on a dyno with trained people watching and listening, perhaps unlikely?

Pocketed pistons using roller cam with:
Lift 544
Dur 318
Dur @ .050 246
LC 110

so unlikely to be physical contact.

Bearing clearance measured at 2.5 thou on assembly. Maybe a little on the large side according to Boosted - I'll know more when I have all journals out.

Bolt - No mention of it loose on disassembly.

[debaron]

Boosted LS1 said:

I have a similar 4.8 build in progress. Bored out to 96 mm plus clearance. Have had to put valve reliefs in the pistons and rebalance the crank. Rods are new, stock 4.6 but have been balanced end to end. Crank has been balanced to suit. I shall look at bearing clearances very closely.

Did you regrind the crank?

[debaron]

Possible culprits then so far:

- Too large bearing clearance + thinner oil
- Warped/ovalled rod
- Oil starvation
- Debris

[debaron]

Boosted LS1 said:

This could have been a build issue clearance wise. From a dyno perspective it could have been curtains in a nano second. The bearings look to have been wiped out quickly without the usual heat marks on the crankshaft. I wonder if journal 8 could have received a tad less oil at a critical moment. I doubt a dyno operator would have had time to save things if he heard any signs of knock.

After talking with several well known builders today the majority verdict is that;

- Using running in oil (10w40) wrong choice I know now but in defence the roller lifters call for no thicker
- While pulling it hard on a dyno on a brand new tight engine

..would likely have caused the engine to spin the most at risk bearing (journal 8)

Like you say Mike this probably happened in a nano and there was nothing that could be done, especially on a fully decatted and sleeved exhaust car making all sorts of noise even if you did hear a knock. Game over.

I have to carry the can here. My bad. I should have made it known the engine was brand new and if I had 20w50 VR1 it may well have been a different story.

I will likely put my high compression 4.6 engine (needs decks skimming and timeserts in the stud threads) back in and work on the damaged 4.8 later.


Thanks for everyones help

[debaron]

stevieturbo said:

Way too little accurate information here.

So some clarity here - Rolling Road not Dyno, I've taken these to mean the same thing - but understood they are different. So engine was in the car and in my opinion would call 100 miles ish a 'new' engine.

The car was being mapped, not just power run, but a power run would have taken place.

No mechanical oil gauge was present, TVR gauge was showing healthy pressure.

[debaron]

Mignon said:

What do you mean by "healthy" ? What psi at what rpm?

Afraid I can't answer that as I wasn't there at the time.

With all due respect I think we're off topic slightly with the minutiae surrounding this.

What I was after was 'can someone with a better/more experienced eye tell me if they agree with the diagnosis of oil starvation or debris' from my (agreeably) not excellent pics. I was not able to get any more pics at the time as the car is 50 miles away.

I've not seen a spun end before so I am politely asking everyone else.

It may well be someone who has seen that before can say ' definitely looks like x to me' but maybe that isn't the case.

Fact is the engine will now come out and apart and everything will be noted so I can work out precise cause and rectify.

Appreciate everyones help so far.

[debaron]

Mignon said:

Until you know the actual pressures you are pissing in the wind.

Thankyou Mignon - an excellent and helpful answer. I don't think I will be able to find out the exact pressure reading during tuning, there will be no records - and yes, I have since been told a capillary gauge is essential during tuning for accurate oil pressure reading. The only info I've been given was that there was 'nothing unusual about the oil pressure - it was healthy at the time' so we'll probably have to make of that what we will.

[debaron]

Kccv23highliftcam said:

If I was you debaron, I'd be ragin...

Still st happens, it's how you come back from it that counts.

Please keep us in the loop how it goes with rebuild and running.

Cheers.

Really appreciate that mate thankyou.

I'm lucky enough to have 3 engines for the car so will be putting the 4.6 back in after a skim and thread repair.

Edited by debaron on Saturday 1st September 18:15

Edited by debaron on Saturday 1st September 18:15

[debaron]

PeterBurgess said:

Seems to be some attacking of dyno operator/s. None of us were there so none of us know. All you can say is that the oil film seems to have broken down and metal to metal contact has occured.The OP justs asks for opinion of why it has failed.
Those saying operator should have seen dip talk rubbish imho. Usually catastrophic failure is more or less instantaneous.
We find race drivers say, oil pressure dipped so I dipped clutch and coasted to a halt so damage should be low...mostly engine full of detritus!
I have had three engines have big end bearing failures in 31 years of running a rolling road dyno, Allowing a low average of 7 per week that is around 11000 dynos, plenty of experience and only three bearing failures! One on a V6 Essex, cause unknown. One on a Grasstracker with a Vauxhall 16v 2 litre, bearings went first run, just after owner/builder said bearings had done 100000 miles and looked fine!!!! The third one was an engine I built which lost pressure at revs and did a bearing, caused by aftermarket filter adaptor being too small, I rebuilt foc even though the adaptor not my supply.
To be honest, if anything sound rattly and we cannot decide it is safe, we don't run it!
I also prefer the owner to be with us, then, if anything goes wrong the customer can see what we have done and the circumstances of failure. The new rollers are good as runs are logged showing max speed atained.
Peter

Wise words Peter thankyou - I hope I'll be able to update on the cause when I finally know myself/