Sea trials before time trials: Our LS3-powered Corvette returns to the track | Project C5 Corvette Z06

J.G.
Update by J.G. Pasterjak to the Chevrolet Corvette Z06 project car
Jun 4, 2021

Now that our C5 Corvette Z06 runs and its LS3 delivers as expected, it's time to take the car to the track. We spent two consecutive Friday mornings at the Florida International Rally & Motorsport Park in Keystone Heights, Florida, putting some miles on the engine and driveline.

Our goal: Look for any trouble spots in preparation for the SCCA TTN. Look for us at the Tire Rack SCCA Time Trials Nationals Powered by Hagerty at NCM Motorsports Park in Bowling Green, Kentucky, the second week in June.

Ironically, the TTN was the final event the Corvette ran before having its LS6 removed, so making the big comeback at this event has us feeling pretty excited.

During these shakedown sessions, we assessed the various systems.

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Engine:

As the dyno shows, the LS3 is nearly 15% more powerful at the wheels than the old LS6. On track, this translates to instant response and a much broader range of usable revs.


Most of our break-in miles were spent driving around the FIRM one gear higher than we normally would, and even then, the car pulled off of corners with enough force that full throttle wasn’t always an option.

BluePrint Engines recommends a 500-mile break-in period for street engines. We didn’t quite get there, but we ran for a total of about 3 hours of track time, varying our loads throughout as much as we could.


A typical session would consist of about 10 laps of fairly easy driving, then a couple hard ones, then a few more easy ones, then a couple hard ones, etc.—lots of rpm variation, and with a close eye on the Holley digital dash to make sure temps and pressures were in check.

We changed the oil once after the initial dyno session, then again after the track testing. We used conventional oil for the break-in, but the final setup will see a dry sump full of 15w50 Driven Racing Oil. Driven’s additive package is specially formulated for motorsport and trusted by some of the biggest names in professional racing, so we’re not going to argue.

Dry Sump:

Speaking of oil, it’s being circulated by that Aviaid dry sump. This being our first dry sump, we’ve come to realize that it’s the automotive equivalent of a granola bar: satisfying, but you can’t so much as look at it without making a huge mess.

Thanks to so many fittings and connections, there are lots of places to check for drips, and opening the system anywhere for an oil change usually results in having to change your shirt at some point. Oil changes are also a bit more complex: There are additional lines to be drained, and accessing the tank drain isn’t exactly convenient.


Gripes aside, the comfort of a steady flow of oil to the engine’s internals is worth any hassle. Pressure is always satisfactory, whether we're accelerating, decelerating, turning left, turning right, or just sitting in the garage revving the engine to hear how cool it sounds. The insurance more than offsets the complexity and hassle.

We did have one adjustment to make to our drive pulley on the oil pump. After running the engine, the belt walked to the back of the pulley on the oil pump until it was barely hanging on.

It looked properly aligned during assembly, and turning the engine by hand seemed to confirm that alignment. But under actual running rpm and load, the belt took a new set. Realigning the belt was as simple as loosening the pulley’s 2mm set screws and sliding it back a bit. Make this one of your first checks after initial startup.

Transmission and Shifter:

Our transmission had been rebuilt and fully REM-polished by GearFX Driveline, and to say it feels like a brand-new transmission barely does it justice.

With some heat in the fluid, the transmission just falls into each gear with a confident stop. The descriptor “intuitive” applies here. C5 transmissions are known to be a bit recalcitrant, but the REM-polishing treatment, which reduces internal friction and heat buildup, and the expert rebuild combine to invite comparisons to Honda S2000 shifting.

Augmenting the transmission’s action is a new B&M shifter that we added while everything was apart. Even if you can’t get your entire transmission rebuilt, you can install one of these gems in about an hour and it’s worth the effort.

So, so many aftermarket shifters out there are absolutely not upgrades. They overshorten the action, making finding gears difficult or changing the relationship to horizontal and vertical motion in the shift action.

The B&M unit nails it, though: just the right amount of reduced throw, just the right amount of leverage, and silky-smooth action. Thumbs up on this one. Thumb on the shifter hand, anyway.

Differential:

GearFX also installed a Wavetrac diff in our C5's stock housing (after REM-polishing everything back there as well), and our initial impressions are wildly positive.

While we haven’t yet really had an 11/10ths session with the car, the action of the gear-driven Wavetrac seems to augment the chassis in the way that only a good diff can.

Particularly during corner entry and trail-braking, the diff lets us vary those corner-approach angles while the rear wheels are slowing at different rates with little to no drama and a lot of predictability.

While we ran in the rear end on conventional oil, our final fill was Motul Gear 300 75w90. Wavetrac has some specific recommendations for best practices when it comes to gear oil, and the company does not recommend using anything with limited-slip additive or friction modifier, which are designed to work primarily with clutch-type limited-slip diffs.

As this is a gear-driven LSD, friction requirements differ somewhat. Wavetrac suggests OEM fluids in most cases, listing the Motul Gear 300 as an approved oil upgrade. So we went with that recommendation.

Clutch:

Maybe the biggest surprise of this whole exercise is the twin-plate clutch setup from Mantic Clutch USA. It’s a delight in every sense. The titanium drive blocks keep the weight down while still providing lots of strength and the ability to handle far more power and torque than we’re even throwing at it.

The action is buttery smooth and light—but not overly light. Actuation effort feels roughly stock, which is impressive given the setup's additional capacity.

More impressive is the feedback, which is akin to what you'd get from a great set of brakes. It’s got awesome feedback on bite point and great response to pedal pressure variations, whether we’re trying to make a hard launch or smoothly load the car onto the trailer.

It’s maybe the first multi-plate clutch we’ve experienced that has yet to show any downside. It’s light, strong and worked out of the box with no shimming required. Lots to like here.

ECU and Dash:

The Holley Terminator has been another lovely revelation, as we’re finding it to be one of the easiest to use and most intuitive interfaces we’ve ever encountered in a standalone ECU.

Install was “mostly” plug and play—we had to switch out a few sensors from those originally found on our LS3, but Holley stocks all the parts necessary and offers strong customer support.

While we left our tuning to an expert, the laptop tuning interface is slick and easy to use, and the handheld tuning adapter provides a lot of control over important engine parameters without requiring you to even worry about the laptop.

The 7-inch digital dash fit neatly into the space vacated by our stereo and looks like an OEM accessory. It ships with about a dozen different gauge designs and layouts, but you can design your own custom layout in minutes as well. The whole package is a user-friendly and clean piece that we can’t recommend enough.

We installed our Terminator exclusively as an engine controller. The factory ECU still lives in the passenger-side front fender and controls all functions of the car aside from what’s required to run the engine.

So we still have a working fuel gauge, speedometer (which gets its signal from the transmission) and voltage gauge. Our stock water temp gauge now provides oil temp readings.

We have to clear a few messages from the Driver Information Center on startup—the car’s stock computer thinks the engine isn’t running properly—but otherwise the Holley Terminator X experience is smooth and friendly.

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Trouble Spots:

Not many, really. Tightening a few connections fixed any drips. That was about it regarding any “sorting.”

Like the LS6, though, the LS3 tends to build a lot of coolant and oil temperature. Switching the LS6 to E85 helped reduce those temps, and we’ve now got an E85 tune ready to go for the LS3 as well.


Plus, we have some Sunoco E85-R meeting us at Time Trial Nationals. Unlike most pump E85, this formula always delivers 85% ethanol—consistent fuel for a consistent tune.

We might still take a few additional steps to ensure as much cooling capacity as we can, however. We’ll be adding an oil cooler from Improved Racing, which supplies oil cooling systems to the Spec Corvette series, so the folks there know a thing or two about keeping C5 oil cool.

We’ll also be replacing our stock 195-degree thermostat with a 180-degree or possibly even a 160-degree unit to keep that coolant circulating as much as possible and ensure temps stay in check under load.

But aside from those things we’d like to improve, there’s very little that needs to be “fixed.” The pitch on crate engines is that you bolt them in and drive away with a smile on your face. So far, that seems to be our experience. We hope it lasts.

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Comments
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Vajingo
Vajingo HalfDork
6/4/21 4:20 p.m.

That wing....surprise "will the rear bumper cover sustain?"

JG Pasterjak
JG Pasterjak Production/Art Director
6/4/21 4:57 p.m.
Vajingo said:

That wing....surprise "will the rear bumper cover sustain?"

It's on there with the best double-sided tape we could find. The good hobby store stuff, not the cheap Dollar General crap.

Actually the uprights go all the way to the bumper beam and are attached with bolts. They were attached with self-tappers for a while that I intended to use just for positioning then totally forgot to take them out. But they held on really well. I only swapped them out because I spotted them after I took the rear bumper off for another reason.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
6/4/21 5:35 p.m.

LS swaps are so played out. You shoulda put in a Coyote.

JG Pasterjak
JG Pasterjak Production/Art Director
6/5/21 10:07 a.m.
Keith Tanner said:

LS swaps are so played out. You shoulda put in a Coyote.

Yeah but swapping an LS with another LS gives you double credit.

350z247
350z247 Reader
9/16/21 9:59 a.m.

I about died when I looked up how much they charge for their oil coolers. $1,000?! That's Porsche levels of price gouging right there.

David S. Wallens
David S. Wallens Editorial Director
9/20/21 1:15 p.m.

FWIW, I priced oil coolers for my E46 M3. While I saw some around $500, anything aimed at competition seemed to cost like $800-$1100.

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