Rebuilding Our LS1 Engine Again | Project LS-Swapped 350Z

Five years ago, this project started with an engine. In fact, we didn’t even know what car we’d be installing our LS1 in. We just knew that buying the disassembled V8 for just $400 was a decision we wouldn’t regret.

Over the months that followed, we signed up for Daytona State College’s Performance Engine Rebuilding and Machining course, spending our evenings rebuilding the LS1 to turn it into the heart of our 350Z that’s now destined for time trials.

That destiny brought with it the need for more power, so we ordered a new set of Air Flow Research heads and two new camshafts from COMP in hopes of making enough power to be competitive in NASA TT2 competition.

With a pile of shiny new parts in hand, our next step was dyno testing, so we called up our friends at Very Cool Parts. Not only do the folks there have a Mustang chassis dynamometer and LS tuning talent in-house, they also have the patience for us to monopolize them for a few days while testing various cylinder head and camshaft combinations.

It was the perfect plan: Drive to Alabama with the 350Z in tow, spend some quality time changing parts, and drive home with at least 50 more horsepower.

We were determined to have a successful dyno session, which is why we did our homework ahead of time. We checked the basics: fuel, air and spark. We didn’t want something simple like a bad coil pack or a clogged fuel filter to burn valuable time on the rollers. But remember what they say about the best laid plans?

[13 Easy Tips for a Successful Dyno Session]

We also spent some time setting up our AEM CD-7L digital dash, making sure to wire up an oil pressure sensor. That data will be prominently displayed (as well as recorded) whenever the car is running.

Thanks to our LOJ Conversions wiring harness, the car’s factory oil pressure gauge worked well, but it wasn’t very precise: The 350Z’s analog gauge only has five marks and two numbers, 60 and 120 psi, which is fine for a street car but left us wanting more detailed information before doing back-to-back dyno pulls.

Sadly, hooking up the oil pressure sender to our AEM dash probably saved our engine: by telling us we’d already ruined it.

Our LS1 now had noticeably lower oil pressure than before—our HP Tuners logs from startup revealed the bad news. That’s not a big deal if you’ve been driving 200,000 miles. We’d driven less than 200.

Clearly something was wrong, and the only question was how much damage we’d done so far. We got nauseous when we cut open the oil filter and found it full of metal.

Our next step? Call for help, of course.

We phoned Very Cool Parts owner Wayne Presley, explained what happened, and asked what to do before coming to visit. His answer: Pull a main bearing cap and see what stories it has to tell.

So we did, pulling the engine, then the oil pan, then a main bearing cap. The wear pattern showed that the bearing journal was not round. We found a bearing that wasn’t ruined but had definitely seen some bad things in its short life.

Our LS1 officially needed to be rebuilt again, but we weren’t going to tempt fate twice and do it ourselves. Instead, we dropped the engine back into the car (sans oil pan), loaded it into the trailer, and drove to Very Cool Parts anyway. An appointment is a promise, after all, and we don’t have a trusted machine shop here in town. So why not make this Wayne’s problem?

After arriving, we yanked the engine back out and gave it a proper teardown. The news was better than we feared: Sure, there was some metal in the oil pan, but the rod bearings looked perfect, and the main bearings were all still in place, if a bit worse for wear.

Our forged crankshaft, a big-ticket item from K1 Technologies, was unscathed. Bottom line: We’d caught it in time.

But we needed to fix our engine, which meant a trip to visit the experts at Pilcher Automotive & Machine Shop in Chancellor, Alabama.

We knew we were in the right place as soon as we walked in: The shop is always littered with aluminum small-block Chevy engines, many making horsepower numbers well into four-digit territory. Our problem would be a cakewalk for them, at least compared to the billet aluminum block they were welding up when we arrived—a rod had punched a hole through the side of it.

After a quick inspection and a few measurements, Pilcher’s prescribed a course of action: They’d line-hone our LS1, install a fresh set of bearings, and blueprint the tolerances to build an engine that should hold up to racing.

Didn’t we already do that when we built the engine? Well, no. Because everything measured in spec, or at least we thought it did, we’d skipped honing our block’s mains and assembled it without any additional machining.

Pilcher’s theory for why it had broken revolved around this oversight: Substituting ARP hardware increased the clamping force compared to the OEM main bolts, which meant our main bearings were no longer round when we were racing our 350Z, causing the premature wear and drop in oil pressure. Of course, they added a caveat: “That’s assuming nothing else is wrong; are you sure your oil pickup is healthy?”

We weren’t, but we’ll get to that later. For the moment we left our LS1 at the machine shop and hoped rebuild number two would last longer than our first attempt. 

Just 36 hours later, we were back at Pilcher’s to pick up our freshly honed and cleaned engine block. A full set of shiny new main bearings were already installed and the main caps torqued to spec.

We felt good about paying the experts for assembly, especially after we learned that they’d used different thicknesses of main bearings to get the perfect tolerance on each.

How much for the work? Let’s just say that we need to profusely thank Pilcher’s for going easy on our wallets while doing a month’s worth of work in just a day and a half. Next time we need an engine built, we’ll head back to Alabama.

Back at Very Cool Parts, we went to work turning our block back into an engine. But we did it knowing there was a killer on the loose, and we needed to find it before it struck again: We still didn’t have a great explanation for the source of that metal in the oil filter.

Sure, we had our theories: Maybe the metal was left over from a machining process. Maybe it came with some oil we bought. Maybe it came with the oil filter? Maybe we’d just been too sloppy when cutting the oil filter apart.

But these were just theories, and Occam’s razor pointed to a much simpler explanation: We’d screwed up, and our engine was grinding itself apart every time it ran. We just needed to find our mistake before the valve covers were back on.

So we tip-toed through the reassembly of our LS1, installing a piston and rod, spinning the engine two full revolutions, then moving onto the next to start the process over again.

We did find one problem: a chipped bolt head on one of the ARP connecting rod bolts. We chalked that up to hasty 1 a.m. removal with an impact gun and grabbed a replacement from Pilcher’s spares pile.

After crawling through the rotating assembly, we installed our new COMP Cam and a fresh Melling M295HV oil pump. Factory LS oil pumps tend to cavitate at higher engine speeds—we’ve heard 6200 rpm is the safe upper limit—but this high-volume Melling part should offer less cavitation and more consistent oil flow even at high engine speeds. We’re hoping it will tide us over until we have time to make the switch to a dry-sump system.

So far, so good: Our engine spun freely and everything was happily returning to its old home.

Then we put the oil pickup on, spun the engine through its first revolution and… TINK.

Damn. A closer look revealed a slight nick in the oil pump pickup, which matched up nicely with the ARP connecting rod bolt we’d replaced.

Turns out we hadn’t knocked the bolt head off with an impact gun: We’d ground it down on our oil pickup. We’d found the source of our metal. These K1 Technologies rods are beefier than the stock parts, and that extra material raised the bolt just enough to interfere with our oil pickup tube.

But just because we found one problem doesn’t mean we’d found them all. Whacking your oil pickup with a spinning connecting rod isn’t great for its geometry, and some modeling clay confirmed that our pickup was pressed firmly against the bottom of our oil pan. Not only was our engine using its pickup tube like a mandolin, it was trying to suck oil through a closed door, too.

While the problem was bad, the fix wasn’t: Wayne spent 15 minutes with a welder and a grinder, returning with a pickup tube that cleared the rotating assembly and kept the proper distance from the bottom of the pan. Hooray for oil filters, but let’s not try this stunt again.

Now that we’d found the culprit, we could have some fun. We bolted on our shiny new Air Flow Research heads, topping things off with a new valley cover from Massive Speed System. This part saved some weight and potential failure points, as it deleted the extraneous Gen III knock sensor mounts in the middle of our OEM valley cover.

All that was left was the valvetrain, and we threw more shiny parts at our LS1 here. We’d originally assembled the engine with Scorpion 1.8:1 ratio rocker arms, which gave our mild cam a bit more lift and duration at the valve.

But now that we were aiming to spin past 7000 rpm—and do it with a burly new COMP cam—we decided to drop back to the gentler OEM rocker arm ratio, 1.7:1.

We couldn’t use OEM rocker arms, however, as they have a tendency to explode when spun quickly. That’s why we installed COMP cams part No. 1981-16, a $650 Max-Life BSR shaft-mounted rocker system designed for cathedral port heads like ours.

This upgrade is an improvement over the factory rocker arms in two ways: First, it features bigger, stronger bearings that won’t come apart with high spring pressures over high engine speeds.

Second, mounting the rockers on one big shaft keeps them pointed in the right direction and helps prevent broken pedestals. Just like we leaned on Wayne for support in these trying times, our rocker arms would lean on each other for support when being thrashed on track.

One problem with these fancy rocker arms: They interfere with the stock valve covers. That added another $215 to our shopping cart, as we needed a set of tall LS valve covers from Holley (part No. 241-164) to finally seal our engine. Unfortunately, they were backordered, so we dropped our LS1 back into the car and headed home to wait for a delivery truck.

We’d spent three days at the dyno without hitting the rollers, instead leaving the shop littered with tools. At least we made new friends at Pilcher’s, right? (Although they probably smiled when we stopped blowing up their phone.) At least we’d avoided catastrophic failure.

Back home, our valve covers arrived and we finished reassembling our 350Z. As promised, the Holley covers fit just like the OEM parts, but with enough room for our huge rocker assemblies. Bonus points for having the coil mounts cast right in place, too, meaning we could save about a pound of weight by throwing out the OEM coil mounts.

And since there was already a Holley truck on its way, we splurged and upgraded to a $450 set of MSD coils, too. We’re skeptical of any claims of increased power with a naturally aspirated application like ours, but we’d already rolled the dice on enough dyno sessions with the nasty 20-year-old coils that came with our engine and figured starting with fresh parts was worth it. Plus, they look great, and we saved about $150 compared to buying eight new coils from the local parts store.

With the engine sealed up again, we were onto the details. We took this opportunity to add some DEI heat insulation to the 350Z’s starter power wire as well as tidy our oil accumulator plumbing a bit with some new Earl’s fittings and tools.

Headers can be rough on plug wires, so we also added a set of DEI spark plug boot and wire protectors, which should prevent our new MSD wires from becoming as crispy as the OEM wires we removed with the engine.

With the odds and ends finally finished, there was one step left: pre-lubing the engine before its first start. It’s important to circulate oil through any fresh rebuild before starting it, and you’ve probably heard the old-timers talking about pulling the distributor to spin the oil pump with a drill on their small-block Chevy.

Since our LS1 drives the oil pump from the crankshaft rather than from the distributor, there’s no way to spin the pump while the engine is in the car, and cranking the engine with the starter isn’t the kindest way to introduce its new parts to each other.

Instead, we used a Summit Racing Engine Preluber. This $170 aluminum tank looks like an air bottle and holds a few gallons of oil and compressed air for pressure. We screwed an Earl’s adapter fitting onto its hose, hooked it to an oil plug on the side of our LS, and pushed oil through the engine for a few minutes.

Then we flipped the switch, pushed the “Start” button and watched the dash: Our LS1 fired right up, making a steady 48.7 psi of oil pressure at idle. We’ll call this mission a success.

What’s next for our 350Z? Now that it has oil pressure, the path forward is clear: We really, really need to hit the dyno. We’ll do that in the next installment.

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