Bearings break up on track due to low oil pressure

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BISH V8
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Bearings break up on track due to low oil pressure

Post by BISH V8 »



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Ian Anderson
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Post by Ian Anderson »

Ouch that sounded expensive!

Are you running a dizzy driven pump?
What oil were you running?
Had you mama need to surge the oil away from the oil pickup in a corner?
Time for a dry sump system?

Ian
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BISH V8
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Post by BISH V8 »

Run pump base mgb with dizzy with accu sump backup
Never had a problem with this set up, but have noticed that oil pressure was running low don't no why yet... Low pressure at 6000 rpm was only 20psi
accu sump was dumping oil in quicker than it could charge, I could see the gauge jumping all over the place,oil drained and finding very small deposits of copper bearing/no steel parts found on magnet, no damage to heads/bore/pistons so looks like bearings but not sure if crank is damaged until pulled out.. Will now run a crank driven oil pump as the pump base cant cope at higher rpm.....
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Post by stevieturbo »

I'd imagine once the accusump has dumped....it would then drain the pump further as it tried to re-charge ? so could actually make things worse ?

What oil ? What oil temperatures ? Do you have a cooler ?

And as others say...does the sump offer good oil control for track racing ?

Was there enough oil in the sump ? For track use running higher can have benefits.
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BISH V8
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Post by BISH V8 »

millers classic performance 20/50 with high z, oil gets changed very regularly
I do run cooler and temp approx. 90/95
Good levels of oil with extra 8 pints in accu sump
Oil pressure low on fast straights no cornering/braking just very low 20psi
at 5800/6000rpm, seems the cause is down to the low oil pressure so possible pump base failure or blockage
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DaveEFI
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Post by DaveEFI »

The 'standard' pump layout was used on engines which revved a lot higher than the larger units can.

If I saw oil pressure down to 20 psi at more than about 3000 rpm on my standard SD1, I'd stop the engine. :D Even more so if it was an abnormal reading. And I tend to ignore the oil pressure at low revs, provided the oil light is working and OK.
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BISH V8
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Post by BISH V8 »

The erratic oil pressure readings were due to the accu sump dumping oil into the engine, I only noticed the readings on a fast straight when the oil went down to 20 psi then shot back upto 50psi from accu sump, I also run a large oil pressure light on my steering wheel which if it came on I would of killed the engine, that's why I put it there in the first place, I am just wondering what caused the low oil pressure in the first place as ive been running the same set up for 6 years with no problems of low pressure, engine gets stripped every 2 years so was due to come out this year..
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oneaves2005
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Post by oneaves2005 »

If it's of use, all the big power MGB's (including mine) in the BCV8 championship are running crank driven pumps (we superfinish ours which makes them feel a lot better on installation). We are revving to 7500-8000 most gear changes and bearings seem really good on yearly rebuilds.

We run around 45-50psi hot (95-100deg) and use Fuchs Titan R Fully Synthetic 15/50.

We are not permitted to run dry sumps but so far, it appears we don't need to.

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Post by Ian Anderson »

BISH V8 wrote:The erratic oil pressure readings were due to the accu sump dumping oil into the engine, I only noticed the readings on a fast straight when the oil went down to 20 psi then shot back upto 50psi from accu sump, I also run a large oil pressure light on my steering wheel which if it came on I would of killed the engine, that's why I put it there in the first place, I am just wondering what caused the low oil pressure in the first place as ive been running the same set up for 6 years with no problems of low pressure, engine gets stripped every 2 years so was due to come out this year..
I would presume the other way around
Something caused the accu sump to dump oil example surge on a corner causing air to be sucked
The accu sump refill opened and overall pressure dropped to 20psi as it refilled
But you were at revs and damage was done at that point.

That would be my guess but I did not even see a lot of keening to assist in moving oil away.

Don't forget to strip the accu sump and clean it before reuse.
Also bin and replace any oil coolers, they never come clean of the debris

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

BISH V8
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Post by BISH V8 »

oneaves2005 wrote:If it's of use, all the big power MGB's (including mine) in the BCV8 championship are running crank driven pumps (we superfinish ours which makes them feel a lot better on installation). We are revving to 7500-8000 most gear changes and bearings seem really good on yearly rebuilds.

We run around 45-50psi hot (95-100deg) and use Fuchs Titan R Fully Synthetic 15/50.

We are not permitted to run dry sumps but so far, it appears we don't need to.
Thanks for info, I don't think ill ever find out what caused the low pressure at high rpm, I had already decided to go the crank driven pump route on my next strip down as items have already been purchased think Ill go the electric water pump route to maximise power, like ive said before never ever has an issue with low oil pressure and at one point when I came in my low pressure light came on when I was about to kill engine, that being 10psi
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BISH V8
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Post by BISH V8 »

cleaning out an accu sum, just wondering would this work??
can you open the shrader valve of accusump, use a clean rod to push the piston inside all the way to air inside, fill accusump with oil, shut it on the oil side, then charge the air inside to 80 psi then open oil valve and flush accusump,do this a few times surely this would work without stripping an possibly damaging o rings/seals
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DaveEFI
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Post by DaveEFI »

I'd say you're wise to look for a reason other than the oil pump itself.
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BISH V8
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Post by BISH V8 »

the pressure relief valve in the oil pump has stuck open against the bypass spring as the cogs are worn on the ends and small debris has stuck it open, this allowing excessive oil pressure to fully bypass the lubrication system and return directly to the sump when excessive oil pressure is generated at high rpm, this would make sense with low oil pressure at high rpm
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BISH V8
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Post by BISH V8 »

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