LSX oil drain back question.

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jed
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Re: LSX oil drain back question.

Post by jed »

RW TECH wrote:
jed wrote: The LSX are notorious for
Spinning number 2 and 4 main bearings.
That's a crank issue. Oil aeration & starvation would result in rod bearing failure first.
What do you mean it's a crankshaft issue??
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Re: LSX oil drain back question.

Post by Cubic_Cleveland »

RW TECH wrote:
Cubic_Cleveland wrote:We are using a GM LSX block in a build for a customer. It's a street strip deal, using a wet sump (Melling 10295 pump) with more of a focus on street driving. The block only has two ½" holes in the centre of the valley for oil return from the heads one at the front and one at the back.

I'm happy to run vent lines from the crank case to a catch can/rocker covers to relieve crank case pressure, but what are people doing for oil return? I don't think basically one ½" oil return towards the back of the block is enough...
There are a LOT of these blocks in Mastercraft boats & I'm fairly certain they do not have trick drain-back systems. Same with supercharged COPO engines.

Why do you think you need more than the 2 holes?
Mostly from comparing the stock aluminium LS blocks to these. Seems to be far greater area in a stock block for oil return, and windage to make its way to the breathers... plus you don't have to fill up the lifter "compartments" with oil before it will return via the drain hole.
If your experience is different, I'm definitely open to suggestions.
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Re: LSX oil drain back question.

Post by Kevin Johnson »

jed wrote: The LSX are notorious for
Spinning number 2 and 4 main bearings.
RW TECH wrote:That's a crank issue. Oil aeration & starvation would result in rod bearing failure first.
jed wrote:What do you mean it's a crankshaft issue??
Assuming uniform aeration, rod bearings begin to be damaged at about 30% aeration; mains 50%.

The main oiling circuit does not appear to have a configuration that would preferentially supply aerated oil to the 2 and 4 main.
0702gm_06_z+lsx+.jpg
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Re: LSX oil drain back question.

Post by The Dark Side of Will »

Cubic_Cleveland wrote:
RW TECH wrote:
Cubic_Cleveland wrote:We are using a GM LSX block in a build for a customer. It's a street strip deal, using a wet sump (Melling 10295 pump) with more of a focus on street driving. The block only has two ½" holes in the centre of the valley for oil return from the heads one at the front and one at the back.

I'm happy to run vent lines from the crank case to a catch can/rocker covers to relieve crank case pressure, but what are people doing for oil return? I don't think basically one ½" oil return towards the back of the block is enough...
There are a LOT of these blocks in Mastercraft boats & I'm fairly certain they do not have trick drain-back systems. Same with supercharged COPO engines.

Why do you think you need more than the 2 holes?
Mostly from comparing the stock aluminium LS blocks to these. Seems to be far greater area in a stock block for oil return, and windage to make its way to the breathers... plus you don't have to fill up the lifter "compartments" with oil before it will return via the drain hole.
If your experience is different, I'm definitely open to suggestions.
Doesn't the valvetrain oil skip the valley as it drains? IE, there are almost no oil sources in the valley, which means very little drainback area is necessary.
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Re: LSX oil drain back question.

Post by Cubic_Cleveland »

The Dark Side of Will wrote: Doesn't the valvetrain oil skip the valley as it drains? IE, there are almost no oil sources in the valley, which means very little drainback area is necessary.
In a factory block? Yes. There are open areas for the oil to return via the lifter area, not much oil in the valley is correct. There is also more area for crank case pressure to make it to the breathers either in the valley or the rocker covers.

In the LSX block being used, the lifter area has windows into the valley. There is no oil return in the lifter area, and a nice ~.250" lip going into the valley. The only oil return is a ½" hole towards the rear, and another towards the front of the valley. There's a ~1" or so hole to the timing chain area for crank case pressure to make it out.
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Re: LSX oil drain back question.

Post by The Dark Side of Will »

Ahh, ok. I didn't know there was that much difference.
Is it laid out that way to reduce windage losses from valvetrain oil drainback?

Is the LSX intended for dry sump use with the valve covers scavenged?
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Re: LSX oil drain back question.

Post by RW TECH »

jed wrote:
RW TECH wrote:
jed wrote: The LSX are notorious for
Spinning number 2 and 4 main bearings.
That's a crank issue. Oil aeration & starvation would result in rod bearing failure first.
What do you mean it's a crankshaft issue??
What I mean is counterweight-related loading & deflection in the crank is causing distress in those locations.
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Re: LSX oil drain back question.

Post by RW TECH »

Cubic_Cleveland wrote: If your experience is different, I'm definitely open to suggestions.
Circle back to my post...
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Re: LSX oil drain back question.

Post by Cubic_Cleveland »

RW TECH wrote:
Cubic_Cleveland wrote: If your experience is different, I'm definitely open to suggestions.
Circle back to my post...
Thanks. Good to have first hand experience!
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Re: LSX oil drain back question.

Post by jed »

Thanks RW for the clareafection. Could it be a balance problem??
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Re: LSX oil drain back question.

Post by RW TECH »

jed wrote:Thanks RW for the clareafection. Could it be a balance problem??
Not really. It's a not enough counterweight in some places/too much counterweight in others kind of problem.
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Re: LSX oil drain back question.

Post by jed »

RW If u could school me on this I would appreciate it. Please.
So it's not a balance problem? A vibration, harmonic, frequencies brought about by out of balance?
The counter weights are not in the right place causing bending and twisting of the crankshaft
Under loading and unloading?

The crankshafts I have seen with number 2and 4 mains are K1, Callie's, and Manley.
Stock LS cranks are less likely to spin bearings.
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