Our V8-powered Nissan 350Z has been too quiet lately. Sure, it’s still loud when it’s running–really, really loud–but after two back-to-back podiums in NASA’s TTU class, it hasn’t been running much.
Our V8-powered Nissan 350Z has been too quiet lately. Sure, it’s still loud when it’s running–really, really loud–but after two back-to-back podiums in NASA’s TTU class, it hasn’t been running much.
At 1G of cornering an engine runs as if rotated 45 degrees, which puts the outboard bank 'horizontal' for a 90 degree engine. At 1.2G the outboard bank is effectively 5 degrees inverted, and it keeps going from there. As I understand it for the LS, oil in the heads drains back through the lifter galleys, which would be at the effective 'top' for the outboard cylinder head cavity. If that's the case, the outboard head, and at least part of the lifter galley, would have to fill with oil before any of it could start returning to the sump. Which seems like a pretty obvious oiling issue, that could certainly cause or contribute to low oil pressure.
This has had me wondering, not only why aren't more people adding external gravity drains off the heads, but why is it not even part of the oil starvation conversation? It should be rather cheap and easy to do if it works. Am I misunderstanding something obvious about how the oil drains from the LS heads, is there a bigger obvious problem with the engine that means this doesn't make a difference, or is a simple solution actually being completely overlooked by an uncomfortably large portion of the community?
Will you need to create a firewall around the new sump in the cabin?
In reply to Driven5 :
Difficulty: As you go up the ladder in pushrod engine stress-testing, you like to run the valve cover area "flooded" so the valve springs stay immersed in oil. They can get really, really hot.
So it may not be the outside head that has insufficient drainback, but the inside head that is starved of oil.
Either way its bad 
In reply to Pete. (l33t FS) :
You make a good point Pete., but I think Driven5 might be on to something. Extra tall LS valve covers are commonly used to clear aftermarket rocker arms, but I wonder if a couple of drains high on the exhaust sides of those same covers would help with draining oil back to the pan, while retaining some oil to help cool the valve springs when driving straight? So maybe the drains could be positioned so that oil drains back through the lifter galleys when driving straight, and through the added drains when cornering.
Of course, routing the added drains straight down to the pan means oil would just flow upward through them during corners. So perhaps the drains could be routed to the opposite sides of the pan? I.E., driver's side drains to passenger side of the pan, and vice versa. Hose routing could be tricky, but I'll bet possible.
Just thinkin' out loud here...
I always wondered why more cars didn't use electric scavenging pump like the bmw s62 & s85. Not as good as a dry sump but a good solution for a street car.
@chomles and @Driven5: I remember seeing online ~5-10 years ago that someone had plumbed some external oil drain lines on the very bottom edge of their LS heads on a C5 Vette I think. Likely it was on LS1Tech.com, but maybe CorvetteForum.com. I remember the photos and specifically how they needed to have a 2 or 3 into 1 line. It seemed an extreme solution, but perhaps that was a good idea.
In reply to cholmes :
That's the idea, although as I'm thinking about it I think there might be more potential risk than reward to running the lines to the opposite side of the pan. Imagine the engine at a 45* angle with one bank horizontal, the pan angled down at a 45*, and the head cavity on the high side of the cylinders. As long as the oil in the head cavity is higher than the oil in the pan, the head pressure (effective height difference to the head drain outlet or oil level, whichever is higher) would ensure that the lines are full with oil flowing toward the pan. But if you now put it at 50*, or even 55* depending on cornering loads, if not carefully located this could actually result in the outlet effectively starting to go 'up' when run to the opposite side than just running it to the near side and result in reduced return flow.
Of course, this all assumes I'm picturing it at least mostly right in *my* head, and I feel like I'm still missing something as it also seems from what I can tell that there should be more oil left in the heads than I've seen in pics/vids when the valve covers are removed.
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