BP camshaft NEW version

Maruha’s camshafts, in lead with the BP one, have been upgraded. The line-up includes all of them: for NA8C, NB8, NB8 (with VVT).

This time’s new BP camshaft is produced by precision machining and it can respond to our users’ needs.

NA8C・for BP F-cam

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

Slide cam pulley for NA

Available colors: silver/black ; gold/black

NA8 F-cam + pulley set

NB8C (Sr-1) BP F-cam

Duration Lift HLA Base diameter
IN 252° 10.0mm Special lifter needed 33.0mm
EX 256 10.0mm Special lifter needed 33.0mm

Special solid lifter 16pcs set

Special cap shim

From 2.65 to 3.65mm there is a setup every 0.05mm.
16pcs are necessary.

NB8C (Sr-2)・F-cam for BP with VVT

Duration Lift HLA Base diameter
IN 252° 10.8mm Special lifter needed 33.0mm
EX 256 10.0mm Special lifter needed 33.0mm

Special solid lifter – 16pcs set

Special cap shim

Cap shim T=2.65

From 2.65 to 3.65mm there is a setup every 0.05mm
16pcs are necessary.

During the development we checked the engine’s efficiency on the engine bench and then we carried out tests on the chassis dynamo tester, too. It is a high camshaft produced thanks to Maruha’s original approach.

Left: testing in the bench room
Right: tests on the chassis dynamo tester

1. Base circle and lift amount (for NA)

The camshaft has a base circle.
The base circle is the diameter of the camshaft’s round tale part.
In the case of the genuine camshaft the base circle is 36mm.

The genuine NA8C camshaft’s lift amount to the 36mm base circle is IN 8.1mm/EX 8.6mm. In other words, the cam lobe rotates in a 26.10 (IN) and 26.60mm(EX) arc.

Left: NA8C genuine IN camshaft
Right: NA8C genuine EX camshaft

If the base circle is left the same way, then because of the high cam the cam lobe makes a bigger arc and there might be the possibility of interference on the head’s side.

We have to keep in mind the cam’s maximum radius.

In reality, when we check the NA8C head, we can see that at the cam lobe’s clearance, there is dispersion. Around the cam lifter there is strange dispersion at the cast. Even in the case of the genuine cam only a little bit of clearance can be secured.

Left: the set camshaft
Right: seizure during the camshaft’s rotation. Interference on the header side’s lifter hall bream

In other words, with the 36mm base if we heighten the lift amount even a little bit, head interference might occur in the case of some cars.

Maruha made the base circle smaller, the lift becomes high but the max. radius is the same as in the case of the genuine one. We can install it safely and get very good efficiency.

In the case of the F-cam for NA8, which is sold as the most basic model, the IN is 252°・9.2mm / EX 256°・9.5mm high lift.

Left: NA8C Maruha F-cam IN side camshaft
Right: NA8C Maruha F-cam EX side camshaft

(engine performance)

The data below are the data of the BP engine with our F-cam with an NA8 base.
The piston is diverted from NB8, it is a high compression piston. Control happens by Freedom.
The air flow meter is removed, with genuine intake manifold we heighten the intake efficiency.

NA8C BP base

Piston: NB8 (Sr-2) high compression genuine piston (0.25mm OS)
Maruha F-cam (New version)
Freedom control・without air flow meter
Reused genuine intake manifold (not processed)
Air-cleaner exchange
Maxim works exhaust manifold (with catalyst)

Biggest torque 18.4kgf / 6.200rpm
Highest power 184PS / 7.200rpm

2. Base circle and lift amount (for NB8 Sr-1)

The camshaft called high cam is generally distinguished by high duration (duration) and high lift (lift).
However, the NB genuine cam’s high lift is almost not known.
According to the measured value the genuine NB8 (Sr-1) cam’s lift is 9.0mm, but to be able to display its efficiency a higher lift is necessary.

Left: NB8C genuine IN side camshaft
Right: NB8C Maruha F-cam camshaft
The 10mm lift amount has a big role in bringing out power.
It is a street spec.
The maximum radius is the same as in the case of the genuine one, so it is possible to install it safely.

The NB F-cam lift is 10mm and spreading the curtain area of the valve’s surrounding, we can get very good efficiency with torqueful power.
To avoid the troublesome valve timing adjustment, we decided to use the genuine cam pulley.
The base circle is 33mm, smaller than the max. radius, that’s why it can be set up without any worries.
For the installation we need a special solid lifter and cap shim.

3. Cam duration and valve timing adjustment-free

The F-cam’s purpose is street tuning – it was developed for a wide range of users.
For this reason the duration compared to the genuine one is mildly higher, but it has been developed based on lots of data, taking lots of time.
At the time of the camshaft’s installation the most troublesome is the valve timing’s adjustment.
Those users who want to simplify the valve timing adjustment, can use the genuine cam pulley as it is.
When exchanging the head gasket or when thinking about the head grinding’s various conditions, one can purchase a different cam pulley and adjust the valve timing more accurately. We consider different types of needs.

4. Rising of the NB outer shim

The NA’s BP engine uses the oil pressure control – HLA (hydraulic lash adjuster), it is maintenance free, but the NB has been changed to outer shim style, and its follow-up performance has improved.

Left: NB8C the outer shim is being pressed by the cam
Right: the pressed shim rises – it cannot be used

If we use the high cam with this outer shim as it is, it is convenient, but we have to face the base circle and lift amount problem and the outer shim’s rising, so we might decide to use an original lifter.
The outer shim is being set upon the solid lifter’s top.
The merits are the good follow-up performance and if you use a special tool, then even after setting the cam up, you can exchange the shim without removing the cam.

The illustration of the rising phenomenon.
However, the lifter’s balance might be bad and if there is a change in the cam’s profile, the shim can rise easily.
Like this, there is the possibility that under these kinds of hard conditions the shim might break out when we start the engine, which means that we cannot use it safely.

The structure of the genuine NB lifter and outer shim

Maruha arranged a separate solid lifter and used a cap-style inner shim on top of the valve.
The adjustment of the shim during installation is a bit troublesome, but it promotes the lifter’s weight reduction and results in safe rotation.

5. From outer shim-style to inner shim-style

Left: NB8C genuine lifter (outer shim-type)
Right: NB8C Maruha lifter (inner shim-type) / can be used for NA8 too

When you exchange the genuine camshaft for NB (base circle 36mm) with Maruha’s cam (base circle 33mm) with inner shim, the thing that is troublesome, is the shim’s adjustment.

The cam base is being processed by machining, that’s why its radius is 1.5mm smaller than in the case of the genuine one.
One of the characteristics is that if the genuine cam’s clearance is appropriate, we can check the necessary inner shim length by the standard formula.

If we want to secure the same clearance as in the case of the genuine one (genuine outer shim – 0.2mm), then the inner shim’s length becomes the same as the standard value.

6. Weight reduction by solid lifter

When we change from the HLA for NA to an NB outer shim, we might expect weight reduction, but in reality it’s not a too big difference in comparison with the genuine HLA.
Maruha’s solid lifter’s design is completely slim and can correspond to weight reduction.

7. Using NB cam in NA

When we install the NB shim-type cam shaft to NA, because of the HLA we cannot install it as it is. We recommend the usage of the solid lifter set that has been set up for NB. However, there is the possibility of replacing the disassembled HLA with a special clearance collar.
Remove the plunger from the genuine HLA’s center and insert the special collar. Because of the valve’s rising dimension there is some dispersion because of which there is individual difference and so we have to deal with the valve clearance one by one, but the high revolution cam’s efficiency becomes stable.

When using it in NA8 one of the methods is the improved genuine HLA’s lash lock. The cost performance is high.

We recommend this method for users who prefer cost performance.
The F-cam for NB is a high performance cam shaft with a 33mm base and a 10mm lift. Its max.radius is 26.5mm and when installing it in NA, it is necessary to undercut it a bit.

8. Cap shim

It is being set up on top of the valve.
Our shim stock’s range is from 2.00 mm to 3.65 mm, with a division every 0.05mm.

9. Re-usage of the genuine valve spring

When we tested the valve springs one by one we got a lift over 10mm. This amount is enough to get good performance.


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