ECOTEC big ends, why they fail

[portercg]

OK I have a theory about why we are seeing big ends go on these engines at 150k plus. there's a few reasons.

First, the oil pump is right at the front of the engine and it has to take some fairly tortuous paths. If the supply is not perfect then something's gotta go

Second, the crank design, while it's very strong, it's got fairly narrow bearing surfaces, narrow oil galleries and a longish throw. When the engine is revving and working hard, the centrifugal forces can bring on cavitation and metal to metal contact, which will eventually make the bearing wear and fail

Third, someone's not doing regular oil and filter changes. I feel these engines MUST have the oil and filter changed regularly and with the correct grade and viscosity oil. Some will be tempted to use a heavier weight oil than GM recommends. don't do it. PM me if you want an explanation. Make sure you only use a genuine or well known brand of filter too like a Ryco. Some of those cheap ones have bugger-all filtration capability.

If you are buying a used Ecotec I'd also recommend an oil pressure test and if it's not within factory specs don't go ahead.

The best Buick tuners in the USA are happy to go to 100psi oil pressure on hi-po engines to make the big-ends live and would kill you if you did not change the oil every 2,500 miles

 

[cracker]

interesting thread although im not sure i agree about the oil pump there are heaps of these engines with 300 000km on them they cant be too bad.
id have to say number 2,3 are the main reason though for sure.

 

[portercg]

Yeah I know what you mean re oil pump location. The usual rule is 10psi per 1000 rpm but for some reason the V6 needs a bit more according to these US gurus. I have to admit I've done zip with modifying Ecotecs. They were not around when I was turning spanners for a living so the rebuild on mine was more out of curiosity and part necessity.

 

[Tradewind]

Third, someone's not doing regular oil and filter changes. I feel these engines MUST have the oil and filter changed regularly and with the correct grade and viscosity oil. Some will be tempted to use a heavier weight oil than GM recommends. don't do it. PM me if you want an explanation. Make sure you only use a genuine or well known brand of filter too like a Ryco. Some of those cheap ones have bugger-all filtration capability.

That explaination will do me, plenty people done give a hoot about servicing, often the biggest offenders are the first owners, then dude picks up his first ride thinking good second hand vehicle and then motor dies.

Change the oil people and never be tempted to EXCEED book recommendations

 

[killuminati]

What can be done to prevent Reason 1 and 2?

 

[vztrt]

Third, someone's not doing regular oil and filter changes. I feel these engines MUST have the oil and filter changed regularly and with the correct grade and viscosity oil. Some will be tempted to use a heavier weight oil than GM recommends. don't do it. PM me if you want an explanation. Make sure you only use a genuine or well known brand of filter too like a Ryco. Some of those cheap ones have bugger-all filtration capability.

How about if/when the car is getting higher in the km's? Normally your meant to use a thicker oil when the car is beginning to get in the higher km segment.

 

[portercg]

Putting thicker oil in an engine will cut oil consumption to a degree.
The downside is that thicker oil plays havoc inside the bearings with what is called "oil film shear" in the engineering world. This occurs at a molecular level and is the point where the protective layer of oil between the bearing and the journal can't remain as a film and gets "torn". The result is metal to metal contact, and then the engine's life is drastically shortened or it just lets go.
A thicker oil has a thicker film thickness and if the clearances in a bearing can't accomodate the thicker film, it will go metal to metal, especailly when cold.
The most common bearing to suffer from this is the big end, because it has the most stress and is the last bearing in the bottom end to get oil, and also has centrifugal forces to cope with.

face it, if your engine is worn, different viscocity oil will generally not do a whole lot, but it can do a lot worse!

So for your street commy always use the visocity that GM reccommends unless the engine has been specially re-built with different clearances. eg drag, circuit racing/endurance.

Thicker oils also rob your engine or power because of the increased friction. If you want to pick up a few easy kilowatts, try some good synthetic in there

 

[hako]

There are arguments for and against thicker oils - here are some for the defense:
The facts are that using a thicker oil will reduce oil consumption. Most Commodores on the road have done over 200000km and the owners need to reduce oil consumption and not blow smoke. The cost of an overhaul is in the thousands whilst using a thicker oil costs nothing, and a lot of Commo owners are cash strapped.
Old and worn engines will not have bearing clearances so small that they cannot accomodate a thicker oil....otherwise they wouldn't be worn. Synthetic oils shouldn't be used in worn engines - read the label. Whilst a thicker oil may rob an engine of power because of increased friction, a worn engine using thicker oil may aloso produce more power because the rings can seal the pistons in the bore more effectively which is how they reduce oil consumption.
My Commodore is still in good form so I use the recommended 20/50 oil, but give me another few years and I'll go up a grade rather than do a costly overhaul in a car that is worth little more than the cost of an overhaul.

 

[Don Sutton]

If the theory of why the bigends fail is true then the lower half of the shell will be the one that fails, is this true?
There are many engines built that 1] Have the oil pump at the front and 2] have the oil pump at the rear driven off the end of the cam shaft or driven off the distributor drive cam at the rear of the block eg Chrysler V8's that have no engine brg concerns.
There are other factors which can determine bearing life such as oil flow rate and temperature plus crankshaft harmonics. Crankshaft harmonics can induce a rattle in the bearing as the crank oscillates back and forth rapidly in rotation driven by the various power strokes (the crank twists with the torque pulses). There have been engines in the past where they had very large bearings (1948-52 side valve Morris Oxford) where the bearing shell would spin around on top of the other shell and lock the engine. If you viewed the massive crank and bearings you would swear that the engine would last a million miles. As for older engines that are blowing smoke, using a wider viscosity range may help. Bare in mind that not all parts of the engine wear equally and some parts may still have acceptable wear tolerances. Using a heavier oil may cause these parts to be starved of oil thus compounding the problem.