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Old 04-18-2013, 01:33 PM
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Engine Bearings Failure (again) BBC 555CI, OFFROAD

Hello , i have a edelbrock/musi 555 697hp engine, its a Big Block Chevy with DART BIG-M BLOCK, i have a problem with it, it keep failing main bearings, it's the third time in less than 3k Miles, i use this engine for offroading (hillclimbing in sand) i use 0.0023-0.0025 clearance on main bearings on the last rebuild, the engine see big load and like 6000-6500rpm for a long period, im using liquimoly 10w-60 oil, i was using clevite HNK Bearings, i was thinking it isn't too much clearance for aplication?, but i dont know how much is ok.

Sorry about mistake on my english, hope someone can help me

Thanks

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Old 04-18-2013, 03:28 PM
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Hi.
Why don't you contact Pat @ Pat Musi Racing Engines or call him #704-664-7051.
& explain your problem, I know Pat, & he would be more then willing to help
you out.
Rich
www.patmusi.com
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Old 04-18-2013, 04:46 PM
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I already do that, i send the engine to him from my country Chile, He send it back and it last like one month and fail again, i cant sens it to him again cause with the shipping and repair cost is the same as buy a new one , any other help?

pd: this is a edelbrock/musi 555
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Old 04-18-2013, 05:58 PM
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thanks for answer f-bird, i line hone mains with a machine shop here in my city, a good one so no doubt about they job, they also measure al the clearance of the engine.

Maybe is the Oil i was using on it. But i have two SBC for offroad one with a blower 177, 388ci 7psi, and i use the same oil and i dont have any problems on it, and the other is just a 350 with some mods, and i dont have anyproblems too.

On the BBC i put a lot A LOT, of atention all the time on oil press gauge, and it never get off. So i was thinking about too little clearance for the application i use, i guess maybe oil get too hot and the journal expand more than clearance and bearing start to fail?

Thanks a lot for help me.
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Old 04-18-2013, 06:19 PM
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i also check crank last time i rebuild, and i have to get it to 0.010 to get it straight, so you think the oil is causing my problem?, no way about clearance?

No detonation, i was using a msd knocking detector
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Old 04-18-2013, 06:28 PM
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you said hill climb
on top of the oil issue..
look at your oil pan and pick up.. they are not made to be going up inclines like that at that rpm for that long..
even drag cars it's only a few seconds with nose up..
you didn't say you where running a dry sump oil system..
but I'm willing to bet that 1/2 the issue is you having the oil pick up sucking air.. and like f-bird said wrong oil..
you may need a oil pick up that, picks up at the back at the rear pan wall and floor.. and not just dead center of the sump floor.. as the oil is always running toward the rear wall on those inclines.. and you might be sucking the pan dry..
I'd also add an oil Accumulator

Moroso : Category Display

hope this helps.
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Old 04-18-2013, 06:38 PM
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Quote:
Originally Posted by gearheadslife View Post
you said hill climb
on top of the oil issue..
look at your oil pan and pick up.. they are not made to be going up inclines like that at that rpm for that long..
even drag cars it's only a few seconds with nose up..
you didn't say you where running a dry sump oil system..
but I'm willing to bet that 1/2 the issue is you having the oil pick up sucking air.. and like f-bird said wrong oil..
you may need a oil pick up that, picks up at the back at the rear pan wall and floor.. and not just dead center of the sump floor.. as the oil is always running toward the rear wall on those inclines.. and you might be sucking the pan dry..
I'd also add an oil Accumulator

Moroso : Category Display

hope this helps.
Thanks for answer, Pat Musi already put me a pan and pickup for the offroad aplication, i can get some pictures tomorrow and put them here, about accumulator i was looking at ACCUSUMP, is the same thing you linked?
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Old 04-18-2013, 07:13 PM
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im using this oil pump (the model that comes with the engine)
http://www.summitracing.com/parts/me...make/chevrolet
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Old 04-18-2013, 07:32 PM
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How did you measure clearances down to individual 10 thousands place?
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Old 04-18-2013, 07:35 PM
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Quote:
Originally Posted by spinn View Post
How did you measure clearances down to individual 10 thousands place?
I Dont understand the question, sorry.

The Machine shop measure the main and rod bearings clearances
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Old 04-19-2013, 02:40 PM
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.003 on the mains might help keep the bearing cooled better.

I would go to a 10-40 or 15-40 oil.

I would think about an oil cooler along with the Accusump, or even a one or two stage dry sump

I would consider trying the 3/4 grooved main bearings.
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Old 04-19-2013, 07:03 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
No detonation, i was using a msd knocking detector

This does not mean the engine was not detonating. This engine is used under heavy load.
and probably gets hot in competition. Start by looking at the fuel you are using.

Cheap gas DOES NOT SAVE YOU MONEY on a competition race motor.
You could have a perfect built motor and pound the bearings out of it just by using cheap gas.
Start here...
i was using the best fuel here in my country, 97 OCT, engine have like 9.8:1 compression
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Old 04-19-2013, 07:54 PM
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Quote:
Originally Posted by TJ555 View Post
Hello , i have a edelbrock/musi 555 697hp engine, its a Big Block Chevy with DART BIG-M BLOCK, i have a problem with it, it keep failing main bearings, it's the third time in less than 3k Miles, i use this engine for offroading (hillclimbing in sand) i use 0.0023-0.0025 clearance on main bearings on the last rebuild, the engine see big load and like 6000-6500rpm for a long period, im using liquimoly 10w-60 oil, i was using clevite HNK Bearings, i was thinking it isn't too much clearance for aplication?, but i dont know how much is ok.

Sorry about mistake on my english, hope someone can help me

Thanks
My first suspicion when I see the words bearing failure and hill climbing combined in the same sentence is oil starvation at the pump. 6000 and up RPM for sustained periods is pretty severe, small errors in lubrication quickly build disasters at those RPMs. I don't exactly know what you're using for a pan and its internal oil management but off-road where the vehicle is exposed to all sorts of unusual angles very much risks allowing the pump to suck air. A deep sump pan with a lot of baffles and traps around the pickup is helpful along with a good louvered windage tray, crank stripper, and a rear main guard that keeps the oil from creeping up the back of the pan and flooding the rear of the crankshaft. Barring using a deep pan, a hammer head kick out style is the next choice with the same sort of innards. Certainly the bullet proof solution is a dry sump.

Filtration can also be a big issue. Whatís needed are multiple, remote filters that are small enough in micros to stop the grit that gets into an engine when playing in the dirt yet provides enough filter area that they don't put a pressure back up on the pump. Lots of guys believe that running a filter or filters without the filter bypass valve will force all the oil through the filter, this however is not exactly correct. If the resistance against the pump of forcing all oil through the filter(s) exceeds the pressure setting of the pumpís relief valve, that valve opens and bypasses oil either back to intake side of the pump housing which heats the hell out of the oil, or if the pump is modified to bypass back to the sump unless care is taken to absorb its kinetic energy the returning spray can interfere and aerate the oil at the pickup, especially with shallower pans. Where multiple remote filters are used they must be plumbed in parallel so the pump sees itself pushing into the larger surface area provided by the multiple filters. If the pumps relief valve is set very high or blocked in the belief this will force oil through the filter regardless of the resistance, all that will happen is the grit will be forced through the filter medium or that the medium itself will structurally fail and circulate the wreckage with the oil.

You can gain a little protection against dry running by adding an excess of ZDDP, moly, graphite, and even PTFE (Teflon) additives to provide a little dry lube to the bearings for those moments when air gets delivered instead of oil. I have no experience with Liquimoly those that like it from those who don't sound like the usual patter on any oil. If I had a BMW or Mercedes it would get Chevron DELO just like everything from my Beech to my Toro. I wouldn't put Castrol on my wife's sewing machine let alone in any vehicle, so I'm, also, not without my prejudices when it comes to oils.

Bogie
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Old 04-20-2013, 01:22 AM
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Smokey Yunick preached the gospel a thousand times, if the wet sump system is in use and swallows a tiny bit of air, then you will be referring to the engine in the past tense. What is your competition running? Are they using a dry sump system? If they are and your competeing then don't even waste your money. The winners didn't get to the winners circle by being dumb. When were talking angles, were also talking the oil pump swallowing air and it takes very little air to kill the bearings.
The problem your engine has is on the wall. Go with the dry sump and absurb it's cost, if you try to continue with the wet sump you'll spend more money trying to find a way to keep it from destroying itself so you may as well accept the fact that a dry sump system is in order.
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Old 04-20-2013, 10:32 AM
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If the failure is isolated to the mains, its not detonation or lack of oil control, its heat.
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