It was 1973 when Osamu Okazaki set out to design a twin-cam 16-valve head conversion for the Nissan L-series that powered the Datsun 510. Little did he know that this self-founded project he embarked on in the garage of his recently set up company, OS Giken, would put him on the map as one of the most respected engine parts creators in Japan. Despite the impact his work on the little 1.8L four-cylinder had in Japanese motorsport at the time, it’s often the later TC24-B1 head for the six-cylinder version of the L-series that is better know out there. But that’s about to change.

You see, like they have done for the TC24, OS Giken are toying with the idea of bringing the TC16 back, and putting it through the exact same overhaul and re-engineering that the longer 24-valve head has gone through over the last few years. That to me is nothing short of pure genius! While there’s no word yet whether it will actually be signed off and how many are actually being built, it’s obvious they have put a lot of work into it if the prototype engine they had on display at the 2014 Nostalgic 2 Days was anything to go by. As you can see above, they have even cast a new-design aluminium cam cover.

Lift the cover off and like in the TC24-B1Z we saw last year, the whole design has changed significantly from that first batch made in the early seventies. First up the cam caps are now a two-piece design, the OS-logoed pieces that hold down each cam in five separate locations along the head.

Compared to the one-piece items the original TC16 used to employ, they’re smaller, lighter and take up less space. The bucket and shim valve adjusters are off the TC24 too and lighter, therefore helping the whole valvetrain rev more freely.

It’s all finished up with OS Giken cams that can be offered in a variety of specifications all the way up to 306º duration.

This isn’t the first time the engine has been brought back to life per se. Back in late 1998, Tomimatsu-san of OS Giken, after about four years working with the company, came across enough TC16-MA2 parts in the warehouse to build up and restore the head they still had. And that’s exactly what he did, dropping the tuned motor into a donor H501 1800SSS. If you look at the video above, you can see the engine being dropped into the car and the engine revved out to its 8,000+ rpm redline on a test run. If you look closely on the dry-cranking of the engine, you can see the original one-piece cam caps I mentioned before. The original TC16 allowed the L18 to develop 232PS at 8,500rpm, up from 115PS at 6,000rpm. Torque increased by 5.2kgm (around 37lb-ft) but was developed higher in the rev range. These figures are off the first race engine they built which employed different pistons and compression ratio and a slightly higher capacity (1,888 cc Vs. 1,770 cc). Those were some pretty impressive number for 1974 when the engine was first used in racing.

If bringing this masterpiece of a head conversion back to life wasn’t enough, you might have noticed that the little L-series they had on display wasn’t running its stock chain-drive distribution.

This is just another further upgrade that OS Giken have come up with, offering the same cam gear distribution conversion they offer for the six-cylinder version of the L-series and of course the S20.

The benefit here is a much tighter and more precise slack-free operation that old chain drive systems just can’t match and a necessity if you consider they plan to push this engine to 10,500 rpm.

It’s almost a pity all of that gear-work needs to be covered up, but one thing is for certain: you’ll definitely be able to hear it, because as the revs rise, the meshing of the cam teeth create an unmistakable whine that just adds so much character to the overall concoction of mechanical sounds emanating from the engine. I’ll never forget when I heard the first cam distribution conversion done to an S20 at Tsukuba. In fact you can hear it right here!

To cover up the gears, a second aluminium cover has been designed and made up, running the embossed TC16-C1 code, the refreshed engine’s new name.

The display engine was running a pair of Weber carburetors bolted onto the OS Giken intake but if the TC16 follows the same sort of development as the TC24, they might even try converting it to injection and offer that as another option.

We’ll need to wait a little longer to see how this all develops and see when the kit will be offered for sale. As you can probably gather, all of this awesomeness won’t come for cheap, but it’s certainly cool that OS Giken are thinking of their die-hard fans and giving them what they have always craved – and then some!

Dino Dalle Carbonare
Instagram: speedhunters_dino
dino@speedhunters.com