F-cam for NA8CE (HLA adjusted)Mazda MX-5 Miata

F-cam for NA8C・BP

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

Slide cam pulley for NA

NA8 F-cam + pulley set

The basic stance of the development was its easy usage, high efficiency and its price. Even in the case of the new camshaft we have to keep in mind these three basic points.

The cams sold earlier were all rated as high cams, however, the lift was not too good.
In the case of Maruha’s camshaft the lift is being preserved.

Generally, if we manage to get a higher lift, there might be a possibility that the camshaft will interfere with the cylinder head. That’s why you can see the comment "possibility of interference" in the catalogues. Of course this doesn’t occur in all cases but you cannot be sure. However, we want our customers to be able to use their vehicle without any troubles, that’s why we offer a camshaft which will not interfere with the cylinder head.

Left: NA8C genuine INTAKE side camshaft
Right: NA8C genuine EXHAUST side camshaft

Left: NA8C Maruha’s F-cam INTAKE side camshaft
Right: NA8C Maruha’s F-cam EXHAUST side camshaft

The cam is HLA adjusted.
The turning circle has almost the same size as in the case of the genuine cam.
While securing the lift we don’t have to worry about meddling.

In the case of the old models the F-cam was produced keeping cost performance in mind and reprocessing the genuine cam base.
The new version uses the production experiences of the old F-cam and the circle’s diameter is smaller.

Small diameter of the base circle

If we manage to get a smaller base circle, we can gain lift while preserving maximum radius.

This point is the new F-cam’s main characteristic.

Including the conditions such as the valve spring, piston recess etc. an easy tuning can be provided by the NA8 BP engine’s leadership.

Easy usage

When installing the high cam, the most troublesome is the adjustment of the valve’s shim and the valve timing.
The shim adjustment can be carried out by HLA adjusting.
The rest is the adjustment of the valve timing.
Just like in the case of the genuine cam even by using a genuine pulley we can get the recommended valve timing. For that we need to set the position of the knock pin. Even though the idea seems to be easy, it is more difficult than it seems.

We took a lot of time for testing the efficiency and the valve timing on benches and rollers. Furthermore, tests that observed the power and stability of the idling have been carried out too. We haven’t examined only the valve timing, but the cam’s profile too. The cam’s merit is its high performance, but its demerit is an unstable idling.
Even if we don’t spread the duration too much, it is possible to get power and torque.
The profile of the new cam is IN 252°/9.2mm EX 256°/9.5mm.

Users that are well informed about the market might know it straight away.
There is no other cam that could produce a lift that goes over 9.0mm without meddling.
And there is no other cam that could be set to a recommended valve timing with a duration of over 256°and a genuine pulley.

Efficiency check

Let’s take a look at the chassis dynamometer tests.

NA8C BP base

i. Piston: for NB8 (Sr-2) high compression genuine piston (0.25mmOS)
ii. Maruha F-cam (New Version)
iii. Freedom control, without airflow meter
iv. Reused genuine intake manifold (unprocessed)
v. Exchanged air cleaner
vi. Exhaust by Maxim Works (catalyst attached)

Highest torque: 18.4kgf/6,200rpm
Highest power: 184PS/7,200rpm

In the case of the NA8C O/H engine to the skid base we used an NB8 (Sr-2) high compression genuine piston, carried out head surface grinding and set up the F-cam.
To be able to absorb more intake air we removed the airflow meter and control it by Freedom.

This engine is able to produce a power over 180PS. Here we would like to draw the attention to its potential as a tuning cam too.

It is difficult to choose a cam.
If you decide to use it, for sure you want to get high duration. Even if you choose tuning, the most important thing while setup is to keep safety and stability in mind.

Low price

The production order of the cam is setting, molding, trial manufacture, test and mass production. Of course this production has its costs. However, Maruha tries to satisfy its customers with low prices and high quality.

As the valve timing setting is not necessary, we can get high efficiency even without a slide pulley. In other words, we try to reduce the costs of the product and the wage adjustment.

Necessity of the cam pulley

If you want to re-grip the valve timing or if you want to set a tuning valve timing, then of course you will need a slide pulley.

We thought of wide usage that’s why we prepared a special profitable cam pulley set too.


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