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

[227bhp]

You'd have to have a keen eye to make out anything from those pics. You need to clean all the bearings and journals, then take quality close up pics of them, not just some vague attempt as you were riding past on a horseback or whatever.
Dirt? Well only you have the answer to that, you built it. Was it 100% clean or not?

[anonymous-user]

227bhp said:

You'd have to have a keen eye to make out anything from those pics. You need to clean all the bearings and journals, then take quality close up pics of them, not just some vague attempt as you were riding past on a horseback or whatever.
Dirt? Well only you have the answer to that, you built it. Was it 100% clean or not?

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

[anonymous-user]

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.

[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?

[Boosted LS1]

^ It can fk up your piston.

[stevieturbo]

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 ?

[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.

[PeterBurgess]

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

[Mignon]

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

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.

[stevieturbo]

debaron said:

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.

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 ?

[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.

[Boosted LS1]

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.

[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

[Mignon]

debaron said:

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

A very large number of the cases of detonation that I've seen over the years were indeed from engines being set up on a dyno where the "trained people" being paid to supposedly do this properly dialled in too much ignition advance or some other calibration error. In fact I'd go so far as to say a dyno is the most likely place to get detonation because if the calibration is done properly and the engine survives the dyno experience it's very unlikely to detonate afterwards.

As for forged pistons they make not a jot of difference to detonation occuring although they might be able to survive mild cases of it better than cast pistons.

When the cylinder head has been removed and the combustion chambers and piston crowns can be examined then you'll know. There is no point in guessing at this as I've said.

[stevieturbo]

debaron said:

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.

There are lots of "trained" people out there doing all sorts....TBH many would be better off taking a train, far far away lol.

But that rod has taken a beating....the engine must have been making a hell of a racket. So why was it run for so long to allow it to get to that state, with trained people watching and listening carefully on a dyno ?

What was oil pressure like ? Any good pics of all other bearings and journals ?