Category Archives: Fusion 360

Real progress at last

I’ve definitely been working too much. Seven days a week  with just three days off since the middle of September. One of the joys of being self-employed! 

Now that the various projects are delivered I can give the Mantula the attention it deserves.  This means there’s been quite a lot of progress considering this build normally progresses at a geological pace.

Much better than new

In the previous instalment I reported that the engine had been dispatched for a complete rebuild.  Well, it arrived back yesterday looking very smart and probably better than new. It’s still sitting on its pallet,  but I’ll get it mounted on the engine stand tomorrow. There are several important parts to attach too. 

Flywheel and clutch

The flywheel has been modified to accept the ignition trigger ring. Once that’s mounted the up-rated clutch can be installed. 

Flywheel machined to accept the trigger ring

The original clutch was Rover SD1 3.5 litre spec which wouldn’t be able to cope with the much greater torque from the modified 4.6 litre unit.

New heavy duty clutch by Helix Autosport

The front end will get a new water pump along with various brackets and sensors. More on this in a few weeks – I have to modify the serpentine belt routing so that it clears the steering linkage.

Low-profile sump

It was quite some time ago that I had the low profile sump fabricated, so it will be wonderful to finally fit the thing! That can happen as soon as it returns from getting its Zinga galvanising coating.  It’ll also have an abrasion resistant ceramic coating. I’m using the sump as a practice for getting the chassis treated.

Low profile baffled sump

When everything’s fitted I’ll squirt some Double TT into each cylinder to prevent possible condensation rust damage until first start some time next year.

Chassis modifications

The chassis is booked-in for modification during the second week of January. I still have work to do on the rear end design where I’m diverging from the standard Marcos IRS set-up a little. The 3D CAD drawing will be finished next week. I’ll then get the new suspension mounts and various brackets cut out on a CNC plasma cutter.

Inlet manifold design changes

Some time ago I showed the designs for the Jenvey throttle body adapters which I had 3D printed here on the Island.

Original undersized adapter
Inlet adapter in position on the Thor manifold

Unfortunately I made an error by severely underestimating the correct throttle size. Now rather than the original 48mm size I will be fitting 60mm or larger Jenvey items.

Here’s the revised design in Fusion 360. I will probably have to build in some strengthening webs. 

The revised adapter design

These 3D printed items are just for testing, more robust items will be fitted when I’m certain that everything works correctly.

The throttle body size error was noticed by the very helpful Daniel Lloyd from Lloyd Specialist Developments in Warminster. They’ll be setting up the Canems engine management system for me and fine tuning it on their dyno.  

That’s all for now. I’ll try to keep these updates more regular while there’s something going on.



Wow, it’s really been three months since I last worked on the Marcos! Sometimes other things get in the way. So it’s been months of DIY and decorating that has left the Mantula untouched. Hopefully I can get back to it in December. In the meantime here’s a picture…

logo3d (2)

3D printing

Today I collected the results of my experiment with 3D printed parts. In a previous post I showed how I was designing a revised inlet system using two new throttle bodies to replace the standard Range Rover part. The design has matured a little and the geometry is now fixed so it would be great to get the parts manufactured.

The final adapter design in Fusion 360

This is a screen capture from the Fusion 360 CAD program showing the adapters in place on the manifold.


This is the result, printed here on the Isle of Wight by Island 3D Printing.



And here’s one of the adapters with a throttle body attached. The oil filler tube will have to be relocated before I can mount the other side.



I’m still here!

Sorry that I’ve been so quiet for the last couple of months. Progress on the car has been minimal due to other commitments. While I’m out of the country often it been impossible to get anything done.

I’m sure you would prefer to see pictures of the Mantula, but nothing new to show yet. However time hasn’t been totally wasted as I prepare to design the changes for the inlet system.

Fusion 360

The image below shows the work-in-progress on two fronts. The first front is learning to use a 3D parametric CAD system. I chose Autodesk’s Fusion 360 Ultimate. It’s really easy to learn, has an appropriate feature set and is affordable. For any ‘hobbyist’ it is free, at least for now… Better even than that it’s a joy to use. I think I’m becoming addicted.

Second front is the design of the inlet system.


The model still has a long way to go, but I think it’s worth the effort. Drawing the plenum has been a real challenge due to its totally asymmetric, organic design and overall complexity. As you can see I still have three more inlet runners to model, plus all of the fixing points.

The next part is the black mounting adapter with the Marcos logo. This will be 3D printed once the final design has been fixed. The current version needs some rework for clearance.  Of course I will only know the effect on performance once I get to run the engine.

The last part shows one of the Jenvey 48mm throttle bodies. This has been modelled to 0.01 mm accuracy to ensure that the throttle linkage works first time. A really great feature of Fusion 360 is the ability to design joints that are limited to a realistic range of movement. So far I have the throttle opening the correct 83 degrees. This will be eventually joined to the main link mechanism, again with accurate movement limits.

For the next few weeks I will be completing this design work. Then I’ll send the CAD files to a local machine shop for manufacture.

Jenvey throttle  bodies

As mentioned above I’m going to use the excellent Jenvey throttle bodies to replace the original Range Rover item. Here’s a comparison.


Two smaller throttles should give better response than a single large throttle. I can’t wait to find out!