Maruha's BP Camshaft Lineup Mazda MX-5 Miata

We are happy to introduce Maruha’s upgraded camshaft lineup.
Our camshafts, the F-CAMs, enjoyed by so many users for a long time, will be upgraded to more user-friendly ones.
The camshafts for BP engines, released in the beginning, are suitable for NA8C, NB8C and NB8C (with variable valve timing spec).

Billeting the material produces the new BP camshafts and allows a wide variety of cam profiles.
Our products can match your needs.

The F-CAM for NA8C

Duration Lift HLA Base Circle
IN 252° 9.2mm Adjusted 33.6mm
EX 256° 9.5mm Adjusted 34.2mm

The F-CAM for NB8C before M/C (without variable valve timing spec)

Duration Lift HLA Base Circle
IN 252° 10.0mm exclusive lifter needed 33.0mm
EX 264° 10.0mm exclusive lifter needed 33.0mm

The cap shim size is available from 2.60mm to 3.65mm (every 0.05mm)

Making Maruha’s BP Camshaft

Maruha had spent much time and energy before the BP camshaft was released.
For instance, we had enhanced the product performance by repeated tests loading the trial models onto our chassis dynamometer.

Left: Observing tests in the engine dyno room.
Right: Inspecting the prototypes onto the chassis dynamometer to release the refined camshafts.

1. Features of the F-CAM for NA8C (with HLA system)

To design a camshaft, we must consider its base circle first.
It forms the diameter of the camshaft round tail and the cam lobe means its additional lift.
The genuine NA8C contains the base circle of 36.0mm and its maximum lift is 8.1mm(IN) or 8.6mm(EX). Consequently, the top of the cam lift is rotating drawing the circle with the radius of 26.1mm(IN) or 26.6mm(EX), from the center of the camshaft.

Left: Cross-section of the Genuine Camshaft (IN)
Right: Cross-section of the Genuine Camshaft (EX)
However, if we make the cam lift higher without changing the base circle diameter (36.0mm), the top of the lift will draw a larger circle. In some cases, it may interfere with the cylinder head.

Rotating a camshaft. Designing with its maximum radius in mind.

Whenever we check the genuine NA8C cylinder heads, different clearances can be found between the cylinder heads and the cam lifts.
Due to the clearance errors, caused by casting, even the genuine camshafts have insufficient clearances at full lifts.

Left: Proper Setting
Right: Interfering with the Cylinder Head (Lifter hole)

Basically, when the lift with the 36.0mm base circle increases, its top could rub against the cylinder head.

But you don't have to worry, we produce our high lift camshafts with smaller-sized base circles.
They are designed with the same maximum radiuses as the genuine cams.
Our quick attachment cams are suitable for the HLA (Hydraulic Lash Adjusters) system.

The most basic model F-CAM for NA8C specifications is as follows: Duration 252°/Lift 9.2mm(IN) and Duration 256°/Lift 9.5mm(EX).
The F-CAMs guarantee to maximize their performance.
They achieve stable idle quality and smooth daily driving. And surely, you will realize the engine’s reving ability has been rapidly improving.


Left: Cross-section of The F-CAM for NA8C (IN)
Right: Cross-section of The F-CAM for NA8C (EX)
(Engine Performance Data on The F-CAM)

The following data shows you our BP engine performance.
We used the genuine NB8C, but realized specification of high compression with the Freedom ECU.
The genuine engine can increase its performance by excluding an air flow meter from the intake manifold.

(Engine Features)
  1. The high compression genuine piston for NB8C after M/C (0.25mm OS)
  2. The upgraded F-CAM
  3. The Freedom ECU without the stock air flow meter
  4. The stock intake manifold
  5. The refilled air cleaner
  6. Maximworks Exhaust Manifold (with a catalyzer)


Maximum Torque 18.4kgf(about180.4N)/ 6,200 rpm
Maximum Power 184PS/ 7,200 rpm

2. Features of the F-CAM for NB8C (with inner shim)

A high lift valve consists of its enlarged duration and its high lift. For example, the genuine camshaft for NB8C before M/C (without variable valve timing spec) contains a lift about 9.0mm.

We have built up our cams with higher lifts as well as with enlarged duration. Higher lifts than 9.0mm can lead to better high cam performances.

In the case of the F-CAM for NB8C (lift 10.0mm) the valve curtain area is enlarged to improve the IN/EX performance.
The product features provide fantastic street drive with more torque and powerful performance.

Reading this, you might become addicted to the F-CAM.
You do not need to adjust the valve timing and it can be adapted to the genuine camshaft pulley.
The genuine camshaft base circle is 36.0mm.
We designed a smaller base circle: 33.0mm. Maruha’s solid lifter and cap type shim are sold separately.


Left: Genuine Camshaft (NB8C)
Right: Maruha Camshaft (NB8C)
The 10.0mm lift is the key to reach great power. This high lift produces hot street drives.

3. Matching your tastes

Maruha’s F-CAM lineup for street drives has been developed to give you great pleasure while driving.
Its duration is not much greater than that of the genuine camshafts.
The F-CAM is a well-elaborated product.

Have you had any troubles with the valve timing adjustment to attach camshafts?
The genuine camshaft pulley allows the pin position of the cam/rocker to apply our recommended value.

4. Floating-free inner shim

89-97 MIATA engines, adopted HLA (Hydraulic Lash Adjusters), need no maintenance. Since 1998, NB8C was released, the outer shim system has replaced it.
Outer shims work well on a high RPM engine.
It is no big deal in theory to produce high camshafts with outer shims, but Maruha refused the sweet deal.

Left: Genuine NB8C Outer Shims Pressed by Camshaft
Right: Pressed Shims Floated

We put into practice the new specifications with solid lifters, examining the balance between the sizes of base circles and lifts.
And without saying, we have to prevent outer shims from sliding out of lifters.
Shims, kicking out noisy HLA, have the advantage of fast valve movement.
It is possible to exchange the shims with the specified tools without replacing the camshafts.

Floated Outer Shims: Bad lifter settings or camshaft profile changes include the chance of floated shims.
They could lead to a grave risk of dropping shims when you start the car.

Left: Genuine NB8C Outer Shim
Right: Genuine NB8C Lifter

Now let’s talk about our original lifter in question.
Our product, the F-CAM is adopted an inner shim which cap covers the top of the valve.
The lightweight solid lifter can increase RPM safely.

Maruha recommends you to select the F-CAM.
It is a wiser choice than that of having to live with HLA not working at high RPM, or with outer shims with fear of floating.

5. Finding the suitable length of the inner shim

Left: Genuine NB8C Lifter (outer shim)
Right: Maruha’s F-CAM Lifter (inner shim)/ Suitable for NA8C

The F-CAM for NB8C (the base circle 33.0mm), superior to the genuine camshaft (the base circle 36.0mm), improves the shim adjustment.
The radius of the product is 1.5mm smaller than the genuine one because of very precise machining.
Our product is elaborately designed in order for you to find its shim length easily, following the appropriate clearance of the genuine cam.
If you need the same clearance as the genuine one, we recommend you to order the inner shim, 0.2mm thinner than the thickness of the genuine outer shim.
Therefore, by subtracting 0.2mm from the thickness of the genuine product the suitable size can be calculated.

6. Stylish and lightweight specs

Do you believe the genuine NB8C outer shim is lighter than HLA?
NO! Actually, the weights between them have subtle differences because the outer shim is heavy and the top of the lifter requires strength.

Maruha’s F-CAM lineup contains stylish and lightweight solid lifters.

7. Using the NB8C cams for NA8C

Because of NA8C with HLA, the NB8C camshaft cannot be placed directly to NA8C. We recommend you to use our NB8C solid lifter set.

There is a cost savings tip.
The plunger should be removed from the center of HLA and you may press an appropriate collar into the HLA.
Various valve lengths will make you adjust the valve clearances.
It is not a piece of cake, but your car with the high-speed camshafts gains more stable performance.

You can save costs by pressing collars.

The F-CAM, Maruha’s high-quality camshaft, has a 26.5mm maximum radius. In case of putting it on NA8C, it might be necessary to shave the edge of your valve lifter hole.

8. Cap type shim

The F-CAM shim, a cap type, should cover the top of the valve to attach to it firmly. If you place the shim to the center of the lifter side, there is a risk that it drops off while you work.

Our shim lineup ranges from 2.00mm to 3.65mm in 0.05s of millimeters.

9. Who is her soul mate?

Match Made in Heaven

The high-lift and gorgeous F-CAM has only one partner.
Its name is: genuine valve spring!
The genuine valve spring does not include state-of-the-art design, but it acts as a tempered valve spring.
When Maruha examined the genuine ones, it became clear that they can work well with 10.0 or more millimeters cam lifts. Especially, the genuine NA8C BP valve spring with the maximum lift (IN 8.1mm/EX 8.6mm) can withstand loads of 62kgf(≒608N), and with a lift of 10.5mm, it forces up to 75kgf(≒735N).
The valve spring has ample strength to be used in safety.
If you are a NB8C user and plan to try a high rotation engine, the valve spring for NA8C will take you to an AWESOME drive!

10. Epilogue

We have spent a large budget and long period of time to produce the full-grown F-CAM.
As for us, this camshaft is an irreplaceable blessing.
If you decide to tyy our F-CAM lineup, we provide it at a reasonable price.

Visit our F-CAM Page again and again, as we plan on increasing our lines of street performance F-CAM. We also produce race-spec F-CAMs. For more information, feel free to contact us.


Maruha Motors Co., Ltd.
Ushizuma 2095-6, Aoi-Ward
421- 2106 Shizuoka city, Shizuoka prefecture
TEL: 0081-54-294-0076
FAX: 0081-54-294-1312