We have the pleasure of continually developing Dirk’s 1973 Datsun 240z to help achieve his vision of a Z car that is adept on the street and track. Improving the driving experience are our Z Car Garage Big-Brakes, Z Car Garage CV Axles, Silvia 6-speed transmission and a host of chassis and driveline upgrades.
Dirk shares his experience working with us:
“Collaborating closely with Rob and ZCG has elevated the optimization process. Rob will frequently talk me out of a bad idea, or into a good one (like the OS Giken LSD). Sometimes I talk him into a bad idea and it turns out to work really well, like the S15 gearbox. The most fun is when we brainstorm stuff together like turning the catch can setup into an improvised simple PCV system, eliminating all hints of oil fumes from the car while running.”
Datsun 510, 620 and Z car love
Since our last iteration, Dirk as been back to Z Car Garage for a few major projects. Let’s take a look at his Datsun story first. Dirk bought his first Datsun in 2014, a 1970 510, to learn how to work on cars himself. After learning more about the history of Datsun, and the significance of both the 510 and the 240Z in establishing Japanese cars in the American market, he knew he had to own a Z as well.
A year later, the right Z showed up on eBay in Texas, a 1973 in silver gray. After pouring over the photos and talking to the seller, Dirk bought the car sight unseen. The idea was to have a nice Z to enjoy and drive, while continuing to work on the (sometimes not) rolling restoration of his 510. The car was lovingly restored by a dad and his children and in mostly stock condition. Dirk also has Datsun 620 work truck complete with dual-Mikuni’s:
“After installing a Datsun Spirit STR-3 engine with a set of Nismo Mikuni PHH44 carburetors, the biggest weak spots left were the rest of the drivetrain (especially the stock 4-speed transmission, but the Subaru diff had also developed some bearing issues), the stock brakes, and of course the loose nut behind the wheel – but sadly that last component typically takes too much money and time to modify thoroughly.”
After comparing the Z to his Subaru BRZ on the track, it was clear the Z was better at everything except for shifting gears. Since his engine made a healthy amount of torque, but not enough to warrant a CD009 (350z) transmission, Dirk kept looking for alternatives. He also wanted something with slightly closer gear ratios to better suit the engine’s power band. An S15 Silvia 6-speed seemed like the perfect fit and we installed it back in 2019.
S15 6-speed transmission
The first S15 box had some weak synchros, so Dirk sourced another one that was installed with OE trans fluid, as well as a set of fresh OE motor and trans mounts to help with shifter feel and reduce vibrations in the car.
“The S15 transmission fit surprisingly well. ZCG built a custom crossmember to locate it, and the shifter lined up almost perfectly. No transmission tunnel mods were necessary. The modern shifter looked out of place, so ZCG built a custom unit that would look stock, and work with the Datsun competition shift knob. A small 6-speed shift pattern sticker modeled after the one used in the Silvia is the only clue there’s something different going on under this car. And of course the driving experience.”
Making the S15 shifter look factory, we are happy with the result and Dirk’s subtle shift pattern sticker:
The Datsun Comp shift knob complements the steering wheel:
Chassis and Driveline Upgrades
First, there was work to upgrade the steering geometry and suspension. With the car being lowered quite a bit, despite having 1″ RCAs installed, it had a ton of bump steer. Rob installed DP racing adjustable tie rods, removed the front springs, and completely eliminated the bump steer on the alignment rack while moving the suspension through its full range of motion.
New DP Racing tie-rods and in-house alignment:
We also refurbished Dirk’s steering rack with fresh parts from our stash:
With the Z back in the shop for bodywork we took the opportunity to make more suspension changes. New Koni Race shocks from T3 were installed, which were a much better match for the 300# and 350# spring rates than the Koni Sport shocks they replaced (as Dirk initially ordered the coil overs with lower spring rates, he never replaced the shocks after adjusting the spring rates, and the car always felt underdamped, particularly on the not-adjustable compression stroke):
ZCG Big-Brakes and CV Axles
Calipers: Stoptech ST42 4-piston front & rear race calipers (Alum 6061 mil-spec Type III anodized)
Rotors: 280mm x 20.6 with Alum 7075 hats
Pads: Stoptech 309 sport street pads
Blog posts documenting all of our customers running the ZCG Big-Brakes can be found HERE.
A few closer detail shots of the calipers, rotors and hardware:
We removed Dirk’s stock brakes and installed our ZCG Big-Brake kit.
At the rear, the factory drum brakes were replaced with our ZCG Big-Brakes. Factory handbrake functionality retained!
Also visible on Dirk’s Z are the excellent adjustable lower control arms from Techno Toy Tuning.
3 Liter L-Series Power
Unfortunately, the Datsun Spirit engine developed rod knock which was the impetus for a big drivetrain upgrade. Several other parts of the car where refined as well.
The L28 engine was pulled, sent to Rebello, and built into a 3L powerhouse. Dave bored out the 44PHH venturis to a custom 38.5mm, to hit the perfect compromise between peak power and drivability. We also installed a fresh water pump, alternator, new fan blade, OEM fan clutch and fresh air filters. The beautiful DP Racing oil pan remained. More photos in the gallery below:
“The STR-3 already was able to slip the Exedy clutch and we were never fans of the Chromoly steel flywheel. A Jim Wolf Technologies clutch and flywheel combo was installed after first trying a newly developed Kameari single plate street clutch kit, which we both found too loud and racy for this street car. While the JWT pressure plate yielded a different pedal feel that took some getting used too, it was not too heavy and perfectly comfortable to drive in traffic. More importantly, it never slipped under any kind of abuse.”
The clutch hydraulics were replaced to work with new alumimum flywheel/JWT HD clutch combo:
We installed a ZCG-built 4.11 OS Giken limited-slip differential in the R180 along with a custom aluminum driveshaft:
Dyno Tuning
The previous L28 made 202hp/194tq at the wheels with Rob’s tuning. Now with the fresh 3L it baselined at 245hp/226tq with more area under the curve:
Rob tuned the car further on the chassis dyno, setting it up with a very lean idle at Dirk’s request (to minimize gasoline fumes at idle). With A/F optimized and Nismo Mikuni carbs massaged, Rob unlocked another 20hp yielding a stout 265hp/232tq to the wheels:
With gains of 62hp/37tq at the wheels over the L28, Dirk is very happy with the new 3L:
“While the Datsun Spirit engine had a very peppy mid-range and made more delicious induction noises, there’s no argument that the more powerful Rebello engine elevated the car to the next level of performance and fun. The entire setup worked incredibly well together, and we hit an impressive 265hp at the rear wheels, or 60hp more than the engine made in its previous iteration, putting it in the 100hp/liter ballpark at the crank. Not bad for a dinosaur engine on California pump gas!”
Enjoy the dyno video and L-series music!
Sorting
The little things are what we excel at and Dirk had a list for us to knock out. While at ZCG, we replaced the heavily sandblasted OE windshield, and did some rust remediation in the cowl area, as Dirk had started noticing water making it into the interior fan assembly after washing the car. More photos in the gallery below:
The heater and blower motor assembly was refurbished with new ducting seals and lubed linkage:
The headlight switch had also developed some issues where sometimes the lights would turn off completely when switching between low and high beam, and was replaced with a good used example from the ZCG parts stash.
“The headlights now worked reliably, the new engine didn’t consume any significant amount of oil, and the whole drivetrain worked together even better than before with the new clutch and flywheel combo.”
Unfortunately, 7 months and many miles later, Dirk was back after a minor nighttime crash that took out the left fender, front bumper and valance, and dented the hood. After bodywork and paint from our man William from William’s Auto Body, we installed a euro front bumper, used turn signal assembly, cleaned up electrical wiring from alternator through firewall and sorted his Speedhut GPS speedo box.
To improve safety, comfort, and avoid future crashes, Dirk upgraded his headlights to a new set of Holley Retrobrights, and GTR Carbide 2.0 turn signal bulbs front and rear from Headlight Revolution.
“The headlights are a world ahead of the old Maxxima LED units, which themselves outperformed the Sylvania Halogen sealed beams, while staying very under the radar, with their sealed beam-inspired looks. And the turn signals are now highly noticeable, even in the brightest daylight.”
Enjoying the Ride
Dirk’s been driving his Z-car pretty much every day since the latest upgrades, and it’s been working phenomenally well:
“The drivetrain + brakes make it as happy to accelerate as it is to stop, and with the quick, closely spaced shifts and eager engine, it’s fun to do a casual grocery run, and to drive quickly. With the electrical systems and all fumes well under control, it’s truly a car you can do anything with, and probably more reliable than my BMW.”
We loved to see Dirk driving his Z on rallies and fun runs this year. Most recently we joined fellow Japanese vintage car owners on the Tokyo Calling event hosted by Breakfast Club Rally:
Dirk also joined us for a New Year’s Day drive through our favorite Bay Area Backroads:
We enjoyed working with you Dirk and it was rewarding to help improve your Z.
“Some say good is the enemy of great, but that’s true if you think you’re done. I don’t see my Z car less as a “build” that’s done. I’m always developing it, just like continually developing a race car (e.g. my Lemons car, http://instagram.com/bittersc243) to stay competitive. In this case the competition is merely for making the Z into the most fun driving experience I can imagine, and the journey of continuous refinement and improvement is a big part of the fun for me.”
While Dirk works through a few interior projects (new carpets, stereo upgrade) on his own, we’re getting ready to further revise the front suspension/steering, and wider wheel + tire options. Enjoy more photo documentation of our work in the gallery below. Thanks for your support Dirk and LONG LIVE THE Z!
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- Nikon F6 | Nikkor 24-70mm f/2.8G | Cinestill 50D 50 Scanned with Noritsu HS-1800 Lab developed in | Dip and Dunk
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- Mamiya 645E | Mamiya 45mm f/2.8 N | Lomography Color 100 100 Scanned with Epson V750 | Epson V850 120 Lab developed in | Dip and Dunk
