Spun big end bearing - Rover V8
Discussion
debaron said:
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?Mignon said:
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.
Because these old engines ran a long way away from MBT (due to running basic ignition systems) often Pmax is really pretty lame (as was the peak torque output), so it's possible (but unlikely) that an aggressive calibration may have cause oil film overload etc
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.
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
This has nothing to do with it being a "brand new tight engine". Crank bearings don't need to be run in and "tight" is an adjective that applies to piston rings and bores not journal bearings. However you didn't mention to start with that this happened on an engine dyno (pretty important info wouldn't you think?) and you said something about no one seeing the oil pressure light coming on but nothing about a proper gauge being present. No engine should ever be on an engine dyno without an oil pressure gauge being fitted and no tuner worth their salt would ever do this.
Maybe you mean it was on a rolling road dyno and only had the car's own gauges but who knows if you don't explain fully.
If it was being given full beans without anyone knowing if the oil pressure was ok then heads should roll.
Maybe you mean it was on a rolling road dyno and only had the car's own gauges but who knows if you don't explain fully.
If it was being given full beans without anyone knowing if the oil pressure was ok then heads should roll.
Edited by Mignon on Saturday 1st September 10:35
Edited by Mignon on Saturday 1st September 11:46
So it happened a brand new engine on a dyno.....but you also said it happened to a 100 mile old engine ?
So you put it into a car, drove it for 100 miles then removed it do dyno it ?
Way too little accurate information here.
Why was it being run at full load with running in oil ? ( although it is highly unlikely that is a cause of any problems ) Surely those trained dyno experts would know that isnt the best idea ?
So you put it into a car, drove it for 100 miles then removed it do dyno it ?
Way too little accurate information here.
Why was it being run at full load with running in oil ? ( although it is highly unlikely that is a cause of any problems ) Surely those trained dyno experts would know that isnt the best idea ?
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.
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.
Very vague and lacking in detailed information right from the first post hence my initial comment.
I don't know how or why people expect accurate info and answers from those in the know with some half assed pics and comments, it's like handing Michelangelo a ladder, a sweeping brush, telling him to get on with it and be done by 5.
I don't know how or why people expect accurate info and answers from those in the know with some half assed pics and comments, it's like handing Michelangelo a ladder, a sweeping brush, telling him to get on with it and be done by 5.
debaron said:
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.
No, with all due respect, we're trying to zero in on the actual important information without which all of this is just guesswork. This is not minutiae. No one, regardless of expertise, (mine is extensive) can just look at a photo of a shagged bearing and say what caused it in the absence of any other information. The actual oil pressure reading is key. Either it was sufficient or it was not. The V8 is a notoriously low pressure engine at the best of times. General rule of thumb for most makes of high performance/hard worked engines is 10 psi per 1000 rpm up to a maximum of 60/70 psi. Anything much less than 40 psi is a danger sign at high rpm but the Rover can struggle to even get to this when in good nick. There is nothing unusual about the Rover's crank bearings which mean they can survive at lower oil pressure than any other engine. They are a similar size and run similar clearances as anything else. I would suggest that at least 50 psi at high rpm is desirable.With all due respect I think we're off topic slightly with the minutiae surrounding this.
Now that we know it was on the rollers we can rule out surge under cornering and although debris in an oilway is a possibility it is more likely to be low pressure that caused this. There's not too much scoring to the crank so it seems the bearing failed very fast without debris damage preceding it but that's not a cast iron prediction despite my race engine building expertise.
A proper oil pressure gauge is not an option on a performance engine. It's a must for the cost involved. All a warning light tells you is your engine just died a couple of seconds ago. Too late to do anything about it.
The oil grade is not as important as the pressure that the system achieves with it but obviously a thinner oil will give a lower pressure in a given system. Modern cars run happily on 5/30 or even 0/20 but they have the pumps and relief valves to work with that. 10/40 is still a thick oil by today's standards but until you know the actual pressures you are pissing in the wind.
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. 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
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
Just realised I lie, we also had a much used MGB engine run a big end. We helped customer with sifting through the debris. One rod kerknackered and unmeasurable. Other three rods showing three thou ovality and tell tale black burned oil that was able to creep twixt back of bearing and rod.
That makes 4 engines! We have had more hg failures and more valve or seat insert failures than bearings go.
Peter
That makes 4 engines! We have had more hg failures and more valve or seat insert failures than bearings go.
Peter
Kccv23highliftcam said:
If I was you debaron, I'd be ragin...
Still s
t 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. Still s
t 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.
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
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/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
Having slept on 'it', a question for folk who will be much more knowledgeable than me.
Rods tend to fail after a long straight when folk put their foot down exiting the next corner. Engineering tells us the load on the rods doubles when the throttle is closed as the power stroke cannot cushion the piston and rod and bearing anymore. A crack can develop in the rod on overun which propagates to failure as soon as the throttle is opened again. Does this mean that a drop in pressure ( if caused by bearing clearance getting too large) followed by lift off exacerbates the bearing which is failing to fail quicker?
Also, most times drivers tell us of a bearing failure the oil pressure never appeared to drop ,just a nasty rattle. On strip down the failed bearing material has invariably blocked the oil feed from the crank to the bearing so the rest of the engine has full oil pressure and unless the oil pressure is data logged ( we have seen build up to failure on data logged engines after a series of mini pressure dips exiting specific bends on the race track) one would never know, apart from the give away rattle there was a problem
Peter
Rods tend to fail after a long straight when folk put their foot down exiting the next corner. Engineering tells us the load on the rods doubles when the throttle is closed as the power stroke cannot cushion the piston and rod and bearing anymore. A crack can develop in the rod on overun which propagates to failure as soon as the throttle is opened again. Does this mean that a drop in pressure ( if caused by bearing clearance getting too large) followed by lift off exacerbates the bearing which is failing to fail quicker?
Also, most times drivers tell us of a bearing failure the oil pressure never appeared to drop ,just a nasty rattle. On strip down the failed bearing material has invariably blocked the oil feed from the crank to the bearing so the rest of the engine has full oil pressure and unless the oil pressure is data logged ( we have seen build up to failure on data logged engines after a series of mini pressure dips exiting specific bends on the race track) one would never know, apart from the give away rattle there was a problem
Peter
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