- Dec 8, 2011
- 520
Here's another just-for-fun thread.
I'm working on a theory and would like input and anecdotes from our local denizens.
First the background. After several years of abuse in my Supra, my 2006 4.2 finally gave up by spinning the #6 rod bearing. After tearing it down, I found that all rod bearings were scored and the main bearings didn't fare much better. Granted, my use case is not typical, but I want to know what NOT to do next time, so I started talking to many of you here and other people from the old Vortec4200.com board.
I found Marc (boosted 4.2 in a 51 GMC) has been battling lubrication issues with similar results as mine. I found Bruhaba had a similar issue, spinning the #3 rod bearing after installing a supercharger. And the Black Opel racing team finally retired their 4.2 after using it to push an Opel GT past 200 MPH. Also it seems like many of the turbo I5 builds over on 355nation.net end with rod knock. That's the bad.
On the flip side we have success stories, like Denny's Camaro that has been running 13+ psi on his 4.2 for many years. No issue. In fact Chevrolet themselves commissioned a one-off twin-turbo 4.2. So what am I missing?
Here's some data:
Per Consumer Reports, the 4.2 has above average reliability for all years.
Every used 4.2 I've ever seen has horrible varnishing
Lubrication-related failures are common on only modified engines
Of the few changes GM made when making the trailblazer TT, one of them was a higher flow oil pump.
Most 4.2 engine swaps require a custom rear-sump oil pan - usually with reduced capacity (5 or 6 versus 7 quarts stock).
Denny's camaro is the only 4.2 transplant I know that actually increased oil capacity with a massive oil pan.
So my hypothesis is that the factory lubrication system is marginal for standard use and inadequate for modified engines. Even a stock engine will overheat the oil to the point that the innards varnish. If a change is made, such as increasing power or reducing oil capacity, the oil degrades, loses its viscosity and the bottom end slowly eats itself until a rod finally lets go. GM knew this, and when tasked when bumping output up to a not-incredible 400 hp, went right to the oil pump.
This hypothesis will be difficult to prove unless some enterprising individuals here volunteer to start installing oil temp gauges. However, I can say that if the Supra ever lives again, it will be getting an oil cooler and more frequent changes!
I'm working on a theory and would like input and anecdotes from our local denizens.
First the background. After several years of abuse in my Supra, my 2006 4.2 finally gave up by spinning the #6 rod bearing. After tearing it down, I found that all rod bearings were scored and the main bearings didn't fare much better. Granted, my use case is not typical, but I want to know what NOT to do next time, so I started talking to many of you here and other people from the old Vortec4200.com board.
I found Marc (boosted 4.2 in a 51 GMC) has been battling lubrication issues with similar results as mine. I found Bruhaba had a similar issue, spinning the #3 rod bearing after installing a supercharger. And the Black Opel racing team finally retired their 4.2 after using it to push an Opel GT past 200 MPH. Also it seems like many of the turbo I5 builds over on 355nation.net end with rod knock. That's the bad.
On the flip side we have success stories, like Denny's Camaro that has been running 13+ psi on his 4.2 for many years. No issue. In fact Chevrolet themselves commissioned a one-off twin-turbo 4.2. So what am I missing?
Here's some data:
Per Consumer Reports, the 4.2 has above average reliability for all years.
Every used 4.2 I've ever seen has horrible varnishing
Lubrication-related failures are common on only modified engines
Of the few changes GM made when making the trailblazer TT, one of them was a higher flow oil pump.
Most 4.2 engine swaps require a custom rear-sump oil pan - usually with reduced capacity (5 or 6 versus 7 quarts stock).
Denny's camaro is the only 4.2 transplant I know that actually increased oil capacity with a massive oil pan.
So my hypothesis is that the factory lubrication system is marginal for standard use and inadequate for modified engines. Even a stock engine will overheat the oil to the point that the innards varnish. If a change is made, such as increasing power or reducing oil capacity, the oil degrades, loses its viscosity and the bottom end slowly eats itself until a rod finally lets go. GM knew this, and when tasked when bumping output up to a not-incredible 400 hp, went right to the oil pump.
This hypothesis will be difficult to prove unless some enterprising individuals here volunteer to start installing oil temp gauges. However, I can say that if the Supra ever lives again, it will be getting an oil cooler and more frequent changes!
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