Minor changes in F-cam for B6 Mazda MX-5 Miata

IN252° 8.5mmAdjusted
EX256° 8.5mmAdjusted
*In the case of the old type the duration is 248°

The production of Maruha’s camshaft for BP has changed to machining and its profile is new.
In the case of NA6CE and B6 the camshaft corresponds to the genuine reprocessed one.
The lineup corresponds to HLA: F-cam (set of 252°・256°) and the HLA lock type’s inner shim is a set of 264°and 264°.
The NB6C is an outer shim type and doesn’t correspond to reprocessed cams.

Even the F-cams for NA6CE and B6 underwent a minor change.

The early types corresponded to IN248°, however the new spec is 252°.

When comparing the cubic capacity we usually use the bore/stroke ratio.
For example, in the case of a B6 engine (78mm×83.6mm) the stroke compared to the bore is long, that’s why we call it long-stroke engine. However, the BP engine (83mm×85mm) is a short-stroke one.
According to the bore-stroke ratio the BP engine is sometimes called a square type too. We might suppose that the BP engine turns better, however in reality the B6 engine turns way better and the reason lies in the stroke.

In the case of B6 engines the characteristics are the setting of an F-cam profile while stabilizing the idling. In the case of NA6CE the exchange of the air cleaner and all the other necessary things for the induction system have been carried out.
The new F-cam has been set up with a function of being able to absorb a large amount of intake.
There are lots of points that have an important function in securing the intake amount, but the following two are maybe the most important:

1. the shape of the air cleaner
2. existence of the air flow meter

In the case of the air flow meter there might be problems with its control and it’s not easy to remove it, however, many customers might be using air cleaner. Lots of different types are being sold on the market and possibly there are many customers that still use genuine cleaner boxes. Both of these have merits and demerits.
Cleaners of other companies are able to take in lots of air, however, they take in the hot air from the exhaust manifold’s vicinity too.
In the case of the genuine cleaner the possibility of heat damage is small but the intake amount is limited.
That’s why an air cleaner that considers the heat damage and intake too would be the best choice. With these kinds of schemes it is possible to change the efficiency of the engine parts. Even the camshaft’s efficiency becomes better after reconsidering the induction system’s parts.

The NA6CE’s F-cam is not a product that aims for power, but a product that aims for a stable pickup.
Its profile allows it to bring out a very good result even on short circuits.

Recommended valve timing:
The recommended valve timing is 110°at both IN and EX sides.
Even if you reuse the genuine pulley, the valve timing is going to be near the recommended one, but if you aim for more appropriate valve timing a slide pulley has a very good effect. Even in the case of the head’s surface grinding, exchange of the gasket etc. we recommend to use a slide pulley.


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
E-mail: info@maruhamotors.co.jp