7. The first race

We are organized in a motorsport club, the WAC-Lindenberg and we rented a small track for doing some practice. Perfect for the first time hunting for time on a track.

This is a track normaly for carts, but it is wide enough for cars as well. It is ~1000m long.

You never know, what will happen - so a trailer is a good idea...

At the track:

I have added a camera inside, A friend has taken a movie from outside and last we mounted a GoPro to the fender to get the front tyre in the view.
The movie shows from every perspective one round...
Have fun...

The semi slicks Federal RS595 did a good job. They had a very good grip on the front, the rear tyres were a little bit over powered. Hard acceleration out of the turns brings a lot of oversteer. Wider tyres next time...
In the last stint the tyres picked up a lot of rubber - so much, that the steering wheel rumbles a lot. Do not know why...?

The brakes did a good job. No worry about them. Perfect from first to last round.
The suspension felt good as well. You see in the movie, that the wheel does a little compress - and 3 times the way on rebound. Its OK, cause I have a smoother spring at the rear ( 60Kg/cm) as on the front (80Kg/cm) to give the life axle more movement.

Worked well...but maybe a anti roll bar will be a good upgrade to have an additionally option for setting up the car to the track.
Winter job!

Ah, another one: The engine spilled oil out of the crank ventilation. Have to take care for this...

6. Clutch actuation

The clutch pedal is still not as I want to have it. You do not feel the point, when the clutch is releasing. And the movement of the pedal is far to wide.
I estimate, that the size of the clutch cylinder at the pedal and the size of the actuator at the clutch is not fitting. But I do not have a chance to change them. Don´t find the parts I need...
What I can change is the way, the pedal moves the push rod in the clutch cylinder.

I increased the travel of the push rod by 40% with moving the push rod pivot more away from the pivot of the pedal.

Some extension brackets were welded to the clevis, which is srewed on the push rod. 3 holes in the bracket and 3 holes in the pedal allows me to adjust the travel for the optimal clutch relaese feeling.

Built in the pedal box.

What I learned was, that it is very important to have the correct angle between push rod and cylinder. If the angle is to big, it needs a lot of power to operate the clutch. Not good.

I thought already about this, thats why I used brackets to keep the push rod aligned to the cylinder and move only the clevis pin away from the pedal pivot. 

It was only half perfect. In the best setup the clutch still was hard to press. No space for new holes and not interested in making new brackets I had an idea:

Two washers at the lower screw give the cylinder a little angle- this solved all my problems. 

Now the clutch has a good feelable release point and is easy to operate.

It wa a huge effort to figure out how to modify all this...

5. Brake ducts

I decided to make some brake ducts. The holes right and left on the front are ideal for this. On other Mantulas I have seen, that they install additionaly lamps - but I do not need them.

I want to use the complete opening for a duct to feed as much as possilbe air to the brakes.

This is the finished result:

From the beginning:
The wooden block fixes the tube to the body. It can be used for left and right duct. It is important to have both sides equal - optics!

Ad layers of Styrodur, a stiff foam, and glue them together. Use a cutter and a rasp and a lot of feeling, time and try and you get to a very close fitting form.

Cover the form with filler.

The filler shall be min. 2mm thick to be strong enough. This will take a lot of time. On the second duct I only need 7 times filler... perfect.

It shall look like this: smooth and fitting. Don´t look at the green spots - I am not perfect...

Then the form, the tube and the inside of the front have to be covered with wax and release agent generously. Now 2 layers of GRP have to be added inside of the car. Only two cause it is easier to remove if it is a little bit flexible. More laers will be added outside of the car. I used 4-5 layers of 160gr. glass fabric type twill. At the end of the tube 2 or 3 more to make it stiff.
A, a hint: Cut the platic tube along the long side and fix it again with a tape. You can remove it much more easy then...

After it is hard, trim it an it will fit perfect.

As teh front is flipping I need a coupling. A bend pice of alu is the solution I go for...

This is the first test mounting. The tube on the top brings fresh air in the interior. A little bit of the air is for the driver.
I tried to add a duct at the disk as well, but the huge steering angle doesn´t allow it. No chance. So I only blow air on the disks.

4. Upgraded brake

The Mantula already had a uprated brake system. 4 pot calipers with a vented 260mm disk.
Wow... but after driving around some km and force the brake a bit more I found , that stopping 4 times from 100 miles down to zero was enough to smell the brake inside.
Thats a no go!
A closer look shows, that the venting holes are open to the outside - to the wheels and not to the inside - the engine. This prevented the brake disks to get cold air through the veted disks because at the wheels there is a low pressure are caused by the high air flow around the car. So I can not install a forced cooling with a brake ducts from the front of the car.

- Brake disk vent openings are on the wrong side
- Forced cooling is possible only with other disks
- Brake ducts are not easy to install cause the complete front is flipping
- Brake ducts have to be custom made

I started to search in the web a replacement for the disks. Nothing will fit to the original GT6 setup - even the same lump as I already have or much smaller ones.
Then I started searching a brake disk, which will fit inside of 15" wheels, has the vent opening to the inside and will fit the hub.
I ended up with a 283mm diameter and 22mm width disk.

Left is the old setup, on the right side the new one:

Additional to the bigger brakes I ordered the big axles from Cannleys Classic.

From the top:

With the wheels on  you see, that it is the maximum which will fit with this rim. 13" or 14" will not fir anymore.

Bigger brakes is the one thing, the othe ris a good foced cooling for them:
More in the next post...

3. Uprated front suspension

The front suspension of the Marcos Mantula was taken from the GT6 or Vitesse.
A lot more power of the Rover V8 , wider wheels and semi slicks are forcing the front suspension much more.
Some tuners offer impoved kits even for the Mantula.
Canly Classics and Spyderworks are the ones I know...

I already use the upper wishbones from Spydercars with rose joints from McGill Motorsport. Mounted them out of the box - everything fits. Only the price from Spydercars is what did not fit...

Canly Classics offers a upright without the trunnion, a hub made of aluminium and a reinforced axle with bigger bearings. Sounds good, looks good and price is OK.

I was lucky cause they are not always on stock, but I got them 2 weeks later. Some explenations how to install come with the parts. Good to know.

Behind the new one, in front the old one.

So I started to install everything.
To make it short, there are a lot of parts I had to modify until they fit together and although fit to the Mantula speciales.
- Mill a flat plane to the upper screw for fitting the steering lever
    --> see red arrow
- Shorten the cone of the axle on a lathe to allow the big nut to pull it into the upright
    --> see blue arrow
- Reduce the outer diameter of the hub next to the upright to have a clerance to the screw heads.
   It was noted by Canlys, that for the Ford PDC there has to be done some adjustments.
   --> see green arrow
- Shorten the spacer behind the crown nut to have enough room for a splint.
   --> no arrow...

No room for a splint...

See the screw heads blocking the hub

The hub on the lathe

With all this mods it fit perfectly and looks much more stable than the old GT6 lump.

My Mantula has installed the Anti Bump Steer kit. There are welded below the original brackets for the lower wishbones additional ones. I mounted the old bushings (the new ones are PUR) to improve the stiffness of the brackets. 

Maybe its only good for my mind, but... it will not harm anything...

Here a short view on the complete setup with the brake cooling installed.
More about it in another post...

2. Clutch and Flywheel

While driving the first few hundred kilometers I noticed, that the clutch feels strange.
There was no defined release point and you have to press the pedal for a huge way when you want to change a gear while standstill.
OK - a winter job.
I removed the engine + gearbox from the car and unmounted the gearbox from the engine. The flywheel, pressure plate and drive plate looks like this:

The flywheel has an uneven surface at the friction area and a lot of overheating cracks. The teeths of the starter sprocket looks worse. It is already weight reduced to 11kg and balanced after that.

The pressure plate is a original Borg Warner part and looks the same the opposit side at the flywheel. Bad. The diaphragm spring is very soft. The diaphragm spring has curved ends and at the release bearing is a round one as well, it will work, but theses two ends together are not recommended.

The drive plate is vitrified and below the min. thinkness.

The pressure plate and the drive plate have to be renewed while the flywheel can be reworked.

Lets start with the flywheel.
Skim 1mm on the late to remove the uneven surface and reduce some more weight. The over heated friction area is still unven as it was hardend by the heat and the late can not deal with different surface hardness. But it looks better than before...

I ask a friend for plane grinding the surface. He gave me the tip first to exchagne the starter ring gear, cause the schrinking of the ring will push / press the flywheel in another shape as without ring. We talk about 3/10 of a mm from the inner side to the outer side here.

So renew the ring. The old is off and the new is shrinked to the flywheel. Put the ring gear in the oven for 1h at 170°C and the flywheel in the fridge. Easy job.

To fix it even better I welded the ring gear to the flywheel. It didn´t weld well as one side is cast iron, the other steel.

Then plan grinded it. What a surface...

The flywheel is ready for balancing now. This can only be done by an specialist. I will bring it to our lokal shop who does this...

A new clutch is needed. The best would be a AP Racing CP2000-13 for the Rover V8 - but they want to have around 400-500€ for this. Uff.
I bought a cheap bargin on ebay where they offer a 50% uprated pressure plate + a 50% uprated driven plate and a releae bearing for 160€.
Sounds good and I knew, that you get what you pay for... so I wait in suspense what I will get...

The pressure plate and the release bearing looks vera well, but the driven plate is rubbish.
Compared with the original B&W one:
Look at the rivets and the recesses for the torrison springs...

I decided not to use it.

Over Facebook I get contact to Clutchfix Ltd. in UK. Ben Willimas, sale at Clutchfix gave me a hand and offered me a speciale uprated three piece clutch for up to 500Nm. It hase a double diaphragm spring and their HD1 organic friction material, burst tested to 250 °C on the driven plate. For around 350€ it is a well sorted price.
I only bought the drive plate from Clutchfix Ltd.
See here a compare of them: