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LS6-Powered 1974 Datsun 260Z

Datsun show, Chevy go, you'll be sayin' "whoa!"

B.K. Nakadashi
Mar 10, 2016
Photographer: Riley Stair

Riley Stair likes building cars.

Now, he doesn't just like Japanese cars, or American ones, or coupes, or sedans, or something that fits into a clean, pre-defined category. He's not a marque partisan, and he doesn't insist that the alpha and omega of automotive goodness come from across an ocean or across the American plains. He cares not for the purity of keeping the engine and chassis in the same genetic line; he's installed a 12-valve Cummins diesel into his '49 Chevy shop truck, and he dropped a 2.5L inline-six into a late '60s Mercedes-Benz sedan. Riley just likes building cars.

1974 datsun 260z mallen alley carbon gt wing Photo 2/24   |   1974 Datsun 260Z Mallen Alley Carbon Gt Wing

And so while the California native had not built a Japanese car previous to the wraith seen here, it's not because he's excluded it from consideration. "I'd had my eye on the S30 Z for a long time," he says. "But they were getting harder to come by, and I didn't have the means or skill set to build one to my liking. Finally, I got to the point where it was time to do one, and I was ready."

That something? A '74 260Z, bought new by a little old lady and set aside in '89 when a head gasket blew at a tender 38,000 miles; the seller Riley bought it from had plans to restore it but ran into money woes. "It was and is completely rust free—just a clean, original car," he says. "One of the problems with these cars was quarter-panel rot, but that was no big deal since I was gonna flare the fenders anyway. I was lucky to start with a good, solid car—the structural stuff becomes a real pain to repair, and I didn't want unforseen issues to break my budget. Starting with a clean car means you're not just sinking your time into repairs—you get to do the fun stuff, too."

1974 datsun 260z control panel Photo 6/24   |   1974 Datsun 260Z Control Panel

Fun stuff, like sliding 5.7 naturally aspirated, all-aluminum liters and 400+ horsepower worth of Gen III Chevy small-block under the hood. Let's eliminate the obvious positives here—that the dressed Gen III weighed about as much as the tragic 2.6L that came out while offering double-plus power, the lower center of gravity that a V-8 allowed over the upright six, the ability to center the engine's weight in the chassis because it's physically shorter. "Everyone wants to run a Toyota 2JZ or a Nissan RB26, and I wanted to stay true to my roots, rather than the car's. I was raised on eight cylinders; Dad always had cool hot rods. The unavoidable advantage is the power-per-dollar ratio. To match what I have here, 430 hp at the rear wheels, would have cost a lot more with a 2JZ or an RB26. I wanted a good exhaust note, some cam noise, and lots of power; the Chevy LS engine was the motor for me."

1974 datsun 260z mallen alley carbon gt wing Photo 7/24   |   1974 Datsun 260Z Mallen Alley Carbon Gt Wing

The actual engine Riley fell into, however, wasn't just any old LS: It was an LS6 out of an '02 Corvette Z06. "A friend of mine bought a wrecked Z06 with only 4,200 miles on it; it had been sitting in his shop ever since. I wanted LS power already, but this just sealed the deal." The basic engine was sound, but Riley rebuilt the top end to make a bit more power, starting with a Fast 92mm intake and throttle body, ditching the throttle-by-wire setup, an SLP 85mm mass air-flow sensor, and Fast 36-pound injectors feed the beast. He added a Vengeance cam with 0.604/0.608 lift at 0.050, Comp Cams trunion rockers, dual valvesprings and retainers, chrome-moly pushrods, MLS head gaskets, and ARP head bolts. "It's the highest-lift cam I could use in a 5.7L LS," Riley tells us. A dual 3-inch exhaust is fed by handbuilt long-tube headers with 1 7/8-inch primaries.

There's also the Gen III's set-it-and-forget-it factor. "The LS seems to be more reliable than a lot of computer-controlled cars, and that has to be a factor in its popularity," Riley figures. "I have lots of friends into drifting, and not only do they not make the power, they're always breaking. The LS is relatively untapped: It doesn't take much to get a bunch of power out. Hell, I could run it on 89-octane if I wanted—and the ability to fill it on pump gas is huge. Plus, at a steady freeway cruise, I'm still getting mileage in the high teens or low 20s." Part of that is the double-overdrive T56 six-speed pirated from an '02 Trans Am: Even with the 3.54 in a stock R200 differential, you're looking at cruising at 1,800 rpm at 70 mph in Sixth.

1974 datsun 260z momo suede nascar steering wheel Photo 11/24   |   1974 Datsun 260Z Momo Suede Nascar Steering Wheel

It's got a full interior, too: Despite the 'cage, it has a stock dash shape and console, working heat, a carpeted floor, and doors with factory-style panel and roll-up windows. It even has a dome light that still works. "One of the goals was to get a race car feel—that bucket seat with harnesses and tubing all around you—but not to gut it and make it a full race car. I didn't want to have to put on a helmet and firesuit to drive it; I wanted to be able to drive it to work if I had to, while bridging the gap between street car and race car."

1974 datsun 260z zg fender flare Photo 12/24   |   1974 Datsun 260Z Zg Fender Flare

Period road tests gave the Z06 a 0-60 time of less than 4 seconds and a mid-12-second quarter-mile, so with its smaller envelope, and given enough traction, this S30 should handily beat those times: "With the 'cage, I figure I'm right around 2,600 pounds wet," Riley estimates. That's a cool quarter-ton less than the Vette, with a stiffer chassis and 430 horses at the rear wheels, not the flywheel-like power measured in Detroit. "Roll into it, and it destroys the tires till you bounce off the limiter. The cam builds from 4,000 to 7,200 rpm, rev-limited at 7,000 rpm. The recommended piston valve clearance is 0.090; I'm at 0.026. I couldn't change the rear ratio; I don't get traction in first, second or third gears as it is. If I put more gear in it, it would be almost undriveable. It could use more tire—it's got the widest rubber I could find, but to be honest traction isn't as fun as smoking the tires." Which might explain why Riley has chewed through three sets of rear rubber inside of about 200 miles. Hooning about has its costs.

The wing on the hatch is a genuine wing used in GT1-class racing competition; it looks wild, but it works—so much so that Riley had to build a front splitter just to prevent the nose from getting light at triple-digit speeds. But for every obvious touch (flared fenders), there is something subtle, almost invisible: Riley frenched the headlights on his Z. Frenching (or tunneling) is one of those things your great-grandpa did to his '49 Mercury back in the day: The light is recessed into the fender for a smoother look. With the advent of flush lights in the '80s, the need for frenching slowly disappeared; here, it's a subtle touch on a car that's, well, not so subtle.

1974 datsun 260z work meister cr01 wheel Photo 16/24   |   1974 Datsun 260Z Work Meister Cr01 Wheel

Everything you see here (save for the wiring as described earlier and the application of the satin black paint, executed at Precision Auto Body in Sacramento) was Riley's doing. His concept, his execution. The rear diffuser? He made that. Motor mounts? Home-built. The 'cage? Pieced together himself from 140 feet of tubing. Not a whole lot out of a catalog for this sort of conversion (yet), so there's a lot of hand-fettling here. But that's OK. Because Riley Stair likes building cars. Perhaps you've heard.

1974 datsun 260z zg fender flare Photo 17/24   |   1974 Datsun 260Z Zg Fender Flare

WHAT IS THE LS6?

GM's new-age replacement for the eternal small-block Chevy, known as the Gen III small-block V-8, launched with the '97 Corvette; it shared the outgoing engine's 5.7L metric displacement, but was 346 ci rather than the traditional 350. In base 345hp form, the first Gen III approached 1 hp per cubic inch—an old-timey yardstick that had not been seen in a naturally aspirated engine in some decades. The Gen III was a blend of old-school and modern thinking: two-valve OHV pushrod orientation with all-aluminum construction, coil-on-plug ignition and throttle-by-wire acceleration. Its alphanumeric code designation: LS1. The Gen III went on to replace the old small-block Chevy in everything, including trucks, into the start of the new millennium.

1974 datsun 260z gm ls6 swap Photo 18/24   |   1974 Datsun 260Z Gm Ls6 Swap

You'd think that whatever came next after the LS1 would be called LS2, but no: The first leap forward for Gen III performance was called LS6. Confusing on its face, but marketing surely had something to do with this: Chevy had another LS6 V-8 in its lineup some three decades previously. At 450 (gross) hp in 1970, Chevy's 454ci LS6 V-8 was among the most feared production V-8s on the street; it was certainly rated higher than anything else, including Mopar's Hemi and Ford's Boss 429. It lasted only a year, but was long revered among your grandparents as one of the most potent engines ever available in a street car. Borrowing the name couldn't be a bad thing.

The Gen III's first high(er)-performance derivative came in the '01 model year, in the Corvette Z06 package: The LS6 still displaced 5.7 liters, but was rated at 385 hp. Small openings were cast between cylinders, to improve main web strength and to help eliminate excess air. The pistons, cast in durable M142 aluminum alloy that was stronger than what was in the LS1, were re-shaped to both reduce noise and increase efficiency. A new pent-roof combustion chamber, ports cast with higher tolerances for increased thermal and volumetric efficiency, and 10.5:1 compression (up from 10.1:1 in the LS1) were expressed with red engine covers that slot in over the on-plug ignition coils.

1974 datsun 260z fast throttle body Photo 19/24   |   1974 Datsun 260Z Fast Throttle Body

There's more. Exhaust manifolds were redesigned, with thinner walls to lighten things up slightly. A new billet-steel camshaft opened valves more quickly, and for a longer duration than stock, and valvespring rates were increased as well. Fuel injectors are 10 percent larger than those on the LS1, the PCV valve was relocated, and the aluminum valley cover had specific baffles and drainage, designed to improve the oil system's capabilities under vigorous and sustained cornering.

That was the first Gen III LS6. For 2002, GM's engineers made another round of improvements that simply weren't ready and battle-tested for the Z06's launch. The mass airflow sensor had a gridwork designed to smooth airflow; this was eliminated and was paired with a larger air cleaner housing. A pair of small catalytic converters was removed to reduce exhaust backpressure. More attention was paid to the valvetrain: The valve stems were now hollow, though the exhaust valves were filled with a liquid designed to aid in heat transfer; valvesprings grew stronger again; camshaft lift was increased to the highest ever built into a factory small-block Chevy V-8. This version of the LS6 lived on in the Z06 as well as the first year of the Cadillac CTS-V.

1974 datsun 260z fuel cell Photo 20/24   |   1974 Datsun 260Z Fuel Cell

And just like that, you had 405 hp at the flywheel, fully dressed. That makes 1.17 hp per cubic inch—well above the 1-horse-per-cube metric often used to factor a performance car. All of that, plus buyers got a three-year, 36,000-mile warranty from the factory. Today, of course, GM puts 400+hp V-8s in its SUVs just to lug their lardy 5,000-pound asses around town. But in a 3,300-pound two-seater, more than a dozen years ago, that kind of factory-warranted power was mind blowing.

I DREAM OF WIRES

High-lift cams and EFI don't generally play well together, but according to owner/builder Riley Stair, some engine tuning and wire pruning made it all work in this LS-powered S30. In fact, the LS6 as seen here is still running an OBD-II port. Riley credits Mark Romans at Don's Motor Machine in Carmichael, California, for making it all work. "He took the harness apart—stripped it all down. GM harnesses are simpler than on some other cars, and a lot of it is emissions related. I'm only running the pre-cat 02 sensors, for example, since this car has no cats, so you can go in and remove the entire pin from the ECU. When it's tuned, it doesn't even know it's supposed to have rear 02 sensors. The TPS and MAF sensor are operating as they would. The Z06 was a throttle-by-wire car, so I took out the electric throttle body and pedal and converted it to drive by cable, then removed the portion of the harness dedicated to the throttle-body sensor and the accelerator pedal. We also removed the alarm and the EWS. The tuner had to leave all of that information out when he re-flashed the computer. The good news is, pretty much any problem you have, you can Google it and come up with an answer. The LS world really made things a lot easier. The engine still thinks it's in a Corvette."

1974 datsun 260z headlight Photo 24/24   |   1974 Datsun 260Z Headlight
By B.K. Nakadashi
31 Articles
LS6-Powered 1974 Datsun 260Z
Tuning Menu
Owner: Riley Stair
Hometown: Folsom, CA
Occupation: Fatty Burnouts
Engine: '02 GM LS6-spec Gen III OHV all-alloy V8; Fast 92mm intake and 92mm throttle body; SLP 85mm MAF; Vengeance high-lift cam with chrome-moly pushrods; Comp Cams trunion-upgraded rockers and dual valvesprings with retainers; Melling high-volume oil pump; Walbro 255-lph fuel pump; 17-gallon fuel cell; Fast 36-pound injectors; MLS head gaskets; ARP head bolts; dual 3" exhaust with fabricated 1 7/8-inch primary long-tube headers; MSD ignition wires; Koyorad Aluminum crossflow radiator; Flexalite e-fan; Optima Yellow top Battery; Twisted Images aluminum battery tray
Drivetrain '02 GM-spec Borg-Warner T56 six-speed manual transmission, all synchro, R200 rear with welded stock 3.54 gears
Footwork & Chassis: Ground Control coilovers, camber plates and lower control arms with adjustable TC rods; Koni coilover race inserts; polyurethane bushings
Brakes: Wilwood four-wheel-disc conversion with slotted and cross-drilled 12" rotors, four-piston front, dual-piston rear calipers; stainless steel lines
Wheels & Tires: 15x8.5" -72 front, 15x10" -38 rear Work Meister CR01 wheels; 225/50R15 front, 235/50R15 rear Kumho Ecsta (street), Toyo R888 (track) tires
Exterior: ZG flares; Type 1 front air dam; custom front splitter with carbon winglets and canards; Mallen Alley carbon GT wing with custom ends; custom rear diffuser; Frenched headlights with black wire mesh stone guards; bodywork by owner
Interior: Sparco Evo 2 seats; Simpson SFI cam-lock harnesses; MOMO suede NASCAR steering wheel with Woodward quick release; Auto Meter Phantom gauges; Hurst shifter; Twisted Images hydraulic drift brake; Wilwood adjustable proportioning valve; hand-built welded-in roll 'cage; aluminum 17-gallon fuel cell

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