This page is all about one man and his vision. The head of OS GIKEN corporation Mr OKAZAKI OSAMU (  岡崎 匡治 ). A remarkable man who developed remarkable cylinder heads. Though these heads were designed 30 years, they are still competitive and extremely desireable today. Truly the stuff of legends.  Today OS GIKEN is a highly respected after market performance parts developer continuing the extremely high standards stated all those years ago.

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These shots are from Tunerzine.com and taken at Tokyo Auto Salon

OS GIKEN TWIN CAMS

This document has been produced to increase awareness of OS GIKEN company’s long history of excellence in engineering. Most of the pictures come from OS sales literature and from the excellent  Japanese retro car magazine “Nostalgic Hero”. It has been produced as a rewritten story and is not a direct translation. For accurate information you should have the website information professionally translated.  If there are any objections to use of these pictures contact me at feral@datrats.com.au  

SOME HISTORY

The Nissan L series engines have probably had more competition success than most other Japanese engines. Their performance at times has equalled and often exceeded, that of famous European Marques including Porsche, BMW and Alfa Romeo.

The L series first made its appearance at the end of 1967 in the bluebird 510. Engines offered were L13 1300 cc also the L16 1600 c version. In further evolutions L14, L18, and L20 4 cylinders engines appeared along with L20A, L24, L26 and L28 six cylinders.

The L series engine became renown for its high level of performance, even in stock form. The engine was constructed with large bearings and a steel crank making the engine virtually bomb proof. These attributes made it a great engine for tuners to improve. Soon the L series was winning production vehicle races where ever it was sold. At the same time the Nissan factory had a very active competition department so the results kept coming in.

It was apparent to the tuners of the day that about 100 hp/litre was the limit of the head design and some started to look at ways to improve this situation and get even more from this remarkable engine.

 ENTER OSAMU OKAZAKI  

In 1973 a Japanese engineer OSAMU OKAZAKI realizing the design limitations of the L series engine decided to cast his own cylinder head and use 4 valves per cylinder to make even more power from the L series bottom end.

Two valve engines being produced were very strong up to around 7000 or occasionally 7500 rpm but torque dropped off after this speed due to design problems with the engines. To overcome this problem and let the engine run to 8500 or 9000 the cylinder head needed a 4 valve design. Other designers saw this as well, so other 4 valve engines were being developed including Nissans LZ 4 valve and others.

At OS, the problem was seen as designing an engine that would run strongly to 9000 rpm and do it smoothly. As a starting platform the L18 bottom end was chosen due to its exceptional strength and simple construction. And so the project began. To maintain superior quality, even the smallest design feature had to be checked and signed by Mr OKAZAKI. This meant he was able to have confidence in all facets of his engine design.

 Technical Details of TC16 MA2

The T16 MA2 has a bore of 87.8  and a stroke of 78 mm, this gives a swept volume of 1888 cc.

These engines have also been done with 88.5 mm bores. The valve system uses cams acting on extremely short rocker arms. Both cams are encased in alloy cam carriers bolted to the head. The valves have an included angle of 20 degrees to the combustion chamber. The inlet valves are 34 mm and the exhausts 30 mm. The camshafts are lubricated by spray bar and give 294 degrees nominal duration for the milder cams and the race camshafts have 306 degrees duration.

In the original MA1 engine, the pistons used were from the LZ16 formula pacific engine. The carburettors were 2 x 48 DCOE Webers. Compression ratio was 11.5 to 1 giving a maximum power of  232 PS @ 8500 Rpm and maximum torque 20.7 kg/m @ 6800 Rpm.  In the current  MA2 engine, custom made pistons are used and the compression has been raised to 12:1. or more.

HEAD DESIGN

To make the engine, the cylinder head was first drawn up on blueprints.

The blueprints were then used to give dimensions to a series of wooden negative patterns made from cherry wood. The patterns are placed into special boxes filled with casting sand and sand is packed into the spaces in the patterns. The patterns are contained in a core box to make dried sand moulds for the castings.

When the casting sand is baked and dried; the box is split in two along a join line and the pattern removed from the baked sand. This leaves a void the same shape as the final casting. The pattern clearly shows a negative of the combustion chambers and port runners.

Other small pieces are separately cast such as the camshaft supports. In the picture left,  the cam support pattern is at the base and the final part above.

The camshafts were cast separately from steel.

The moulds made are then filled with molten metal and the cast parts are machined to make the components. This picture shows rejected castings in the back of a truck going for re-melt.  

A bare head and rocker cover are shown right.

 THE ENGINES

TC16

The TC16 twin cam L series first models were all plain cast alloy grey. A surviving example is shown below .

The things that made this engine different from others of its time are the excellent fast-burn combustion chamber shape and simple design of the cam drive system. The dual squish bands on each side of the chamber are still seen in the state of the art engines of today.

The early gear drive for the TC16 MA1 cams is shown beside The straight cut gears were noisy and rattled at idle.

 The picture right shows a TC16 compared to a group 2  L engine.

 From start to finish the TC16 MA1 project cost 20,000,000 yen in 1976.

A right side view of the TC16

TC24 B1

After the TC16 MA1 kit was in put into limited production, the focus was directed to making a six cylinder version of the head.  This became the TC24 B1 head conversion. At the same time the 4 cylinder head was upgraded as well into the MA2. The picture right shows the TC16 MA2 (4 cylinder head) alongside the TC24 B1 six cylinder head

The simplicity of T24 B1 valve train in the later cam drive model is shown beside and below.

Some design changes were made in the TC24 B1 conversion to improve on the MA1 design. This included  an external coolant rail to direct coolant past exhaust valve guides.

 In the rear view of the engine you can see the headers pipes bundled into two groups of three.  1, 3, 5, cylinders feeding into one collector, with 2, 4, 6, into the second collector.

 Pipes are beautifully shaped and similar to the later RB20 GTS-R turbo extractor in the much later HR31’s.

TC16 RACE ENGINE REVIVAL

 This story appears on the OS GIKEN website and I have done my best to translate it keeping to the original as much as possible. My apologies for any errors.  

After joining the OS GIKEN company and learning some of its history, including about the twin cam heads, I was looking around in the warehouse in some old stock corners that had not been disturbed for years and found some parts made for the TC16 engine. Some were marked as defective. I asked if I could repair them and put them together as a project. This was in 1998. The data relating to these parts had disappeared over time and some parts did not appear to be defective at all when inspected. It appeared that all the head parts required to build another head were there and after some discussion I was given the go ahead to make an engine to use as a test bed for our OS products.

From that point my days consisted of work for the corporation and my nights in the garage working on engines including the TC16. This became my life. At the same time as getting the TC16 together, I was building several performance engines for some domestic production cars and foreign imports.

As the TC16 is a handmade engine, it required lots of time, large amounts of fine machining, fine adjustments to component fits and then even more adjustments again till it was perfect.

 Click on the picture left to go to the OS site and download a video of the engine running

When all the components were finished, the engine was built in the garage of a friend over a week

On first attempting to start the engine, some late nights were spent trying to get it to run. It would  backfire badly and refused to run. We tried again and again, the result was always the same – rough firing and would not run.  The problem turned out to be the firing order of the engine is 1 2 4 3, not the more common 1 3 4 2 order used on most engines. With the plug leads in the correct position the engine started immediately and ran very smoothly..

After starting I checked the ignition timing and it was set at 16 degrees. For this amount of total advance the engine was incredibly responsive. It was eventually set to a total advance of only 20 degrees, possibly due to the incredible burn efficiency of the chambers.

The engine is very noisy when idling. The noise comes mainly from the gear drive train and piston noises when cold, but when the engine is revved using the accelerator, there is drastic change in the sound, the previous “noise” becomes a song to lift the heart in the form of a smooth high speed howl!.

On the road, the engine has an abundance of low speed torque. This was entirely unexpected and is possibly good enough to cope with the hardships of city driving. Now wouldn’t it be fun to be driving in traffic at a low idle, flooring it and at a stroke going to 9000 rpm. It brings a new dimension to ones driving.

 Click on the pic left for a video of the datsun 1600 on the race track

The reborn TC16 engine is fitted to a Bluebird H510 1800 SSS 4 door sedan test car revitalised as our test bed and display vehicle at the Tokyo auto salon. The car is fitted with a carbon fibre boot and bonnet.. It was campaigned in the Historic Automotive Festival races and had an easy victory in its class. This shocked its rivals who did not expect such an entry. The competition included the S30Z Nissan works race car fitted with the 300 hp cross flow head 2.9 litre LY engine.  If there were any doubts about taking the Bluebird seriously before, there was not after this and heads were shaking in disbelief.

Because the TC16 is such a high efficiency engine the torque remains strong even over 8500 rpm and up to 10,000 rpm acceleration is still strong. It was planned to only use the engine to 8500 or maybe 9000 rpm. However at 9500 the torque was really strong so the engine is now revved to 10,500 Rpm with joy!

This allowed us to show the LY engined Z car and others a set of tail lights on the straights.

Name:    Mr Tomimatsu

Corporation - OS Engineering and Research ..Super Lock LSD Development Leader
Joined the company  1994

Age: 30 years

Current Cars

• BMW 320 much modified
• BMW 535
• HONDA S800
• Toyota sport 800 (Full restoration by self)
• Mercedes Benz 250CE  (1970)

THE TC16 MA2 POWERED DATSUN H510 SSS ON DISPLAY AT OS HEADQUARTERS.

 This is a 14 page pdf file of the above with full size pictures! 

 To down load click the link    OS TWIN CAMS HISTORY AND DATA  

The document  also includes a rough translation of an article on the OS GIKEN website about the revival of a TC16 MA2 engine in a 510 Datsun 1800 SSS.

Please inform me of any errors I have made in the critical subject materials.