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.
[Surprise podium finish for our 350Z’s competition debut]
Instead, it’s been parked in the back corner of the shop, hooked to a battery tender with a tank full of fuel stabilizer. Why? Because it’s still missing one key ingredient: oil pressure.
We’ve run a giant oil accumulator for years, as accumulators are great, easy fixes for protecting an engine against intermittent oil pressure loss–like from a dry oil pickup in corners.
But looking at the data logs from Roebling Road, our LS wasn’t leaning on its accumulator only intermittently. Instead, it was leaning on its accumulator for seconds at a time, drying out its oil pickup and relying solely on stored accumulator pressure through almost every single corner.
The writing on the wall was clear: Keep running the car without changes, and we’d be building a new engine before much longer.
So how do we fix it? Well, there are a few options.
The first and easiest? Just make the car slower. Pull off some aero bits, switch to slower tires, ruin the suspension setup Andy Hollis so expertly helped us dial in, and perhaps the car’s cornering loads would decrease enough to keep our engine happy.
Yeah, sorry, but no way. When has slowing your race car ever been the right answer?
So let’s move on to option two, which we’ll call the Band-Aids. Basically, were there any tricks left in the book to keep our wet-sump engine happy? We could try a bigger, baffled pan that holds more oil, a fancier PCV system and a big accumulator.
[Video: Are oil catch cans the best solution for PCV system issues?]
And we know we could try those things because the car already has them all, and they’re just not enough. Even with 10 quarts of oil, there’s simply not enough staying where it needs to stay.
There’s only one real option left, and it’s the same option you’ll find on most serious LS-powered race cars in the world: the dry sump. It’s finally time to convert the 350Z.
[Installing a dry sump onto our Corvette’s LS3 engine]
Welcome to the next few months of our life and the next few thousand dollars out of our wallet, but at the end is the promised land: an LS with perfect oil pressure no matter what conditions it’s subjected to.
First, though, we should cover the basics. What exactly is a dry sump?
In a normal engine, the oiling system is fairly simple: An internal oil pump sucks up the oil from a pan at the bottom of the engine. After being pumped up through the pickup tube and then through the engine’s various passages, clearances and bearings, the oil falls back down through the engine, landing in the pan. Then the ride starts all over again. Think “goldfish pond fountain” and you’ve got the basic idea.
Go racing, though, and this system can fall apart in a few ways. First, there’s a big, wide pan of oil, so heavy cornering, acceleration or braking loads can push the oil away from the oil pump’s pickup.
Second, you’re relying on the engine’s internal pump, which the manufacturer designed for a specific operating window. That window probably wasn’t “8000 rpm on track for 20 minutes at a time.”
And third, because there’s only one pickup, it can’t suck up oil that might be trapped in other places in the engine, like the heads on our LS in hard corners.
In theory, a dry sump fixes these issues. Rather than use the oil pan as your oil reservoir, an external tank–usually a tall, skinny one–is used, meaning oil slosh becomes a non-issue. This external tank allows more oil to be carried, too.
Once oil falls back down to the pan, it’s instantly sucked out and put back in the big tank, creating a “dry sump.” Oil from the tank is then pressurized and pumped into the engine by either the stock internal pump or an external pump that can be sized and driven for specific race conditions.
And because the acts of recovering oil and pressurizing it are separated, you can technically have as many oil pickups as you’d like–think two or three or even four little pumps pulling oil from different areas and adding it back to the big tank, meaning the pressure pump has a constant supply of oil to use for your engine.
To go back to our analogy: We’d been racing with a goldfish pond when we really needed to plumb a swimming pool.
Which is why we didn’t design our dry-sump system ourselves. Instead, we called a company that does it all day, every day: Peterson Fluid Systems.
And after an hour or so of chatting and a few questionnaires asking about our engine, our racing, our goals and yes, our credit card number, we received a giant box of dry-sump parts.
Photography Credit: Tom Suddard
But what did we order and why? And could we have just done this project with junkyard parts instead? Over the next few updates, we’ll take a deep dive into how and why we landed on this parts list and how you can convert your own car to a dry sump. Post your questions below, and we’ll do our best to answer them in future updates.
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Comments
Driven5
PowerDork
9/26/24 11:40 a.m.
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 
cholmes
New Reader
9/27/24 2:04 p.m.
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.
Driven5
PowerDork
9/30/24 12:34 p.m.
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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