The V8 Owners Forum -

Hello all,
I'm fitting a Thor 4.6 V8 from a Range Rover into a Marcos Mantula. As far as I know this hasn't been done before so I will have to make a few changes to get everything to fit.

To save time and potential rework I'm going to design the installation in 3D CAD. So what I'm looking for are some accurate drawings of the V8 to get me started. Does anyone know where to find them?
I've almost finished the inlet manifold with its twin Jenvey throttle bodies, but now it will get more complex.

Here's some work-in-progress...

Thats 3D CAD ??

Looks like a photo to me

Top work!!

You are certainly not the first to consider putting throttle bodies on the end of the plenums. A friend bought one to do the same on a Griff 500 - but we quickly realised that it was unsuitable and sold it on before getting past the second design round in the pub!

Thor manifold is designed for low end torque that a heavy 4x4 requires, which is why it has long thin runners. From my Rover v8 Manifold archive Jonathan Douglas of JE Engineering commented:

'the throttle body has a 68 mm throttle as standard and again, we often take this out, in this case to 71.5 mm. The Thor manifold, when used with either a standard cam or a mildly tuned cam, gives a strong torque peak at around 2,000 rpm, much higher than that achievable with the Lucas plenum design, but even with careful gas-flow work the power is limited. We find it difficult to achieve more than around 280 bhp with this manifold, where a similar amount of effort on a Lucas Plenum manifold will yield 320 bhp (but with less torque below 3,500 rpm'

Rover manifold archive:
http://www.mez.co.uk/ms12-new.html

Thanks for the feedback Eliot.
Yes I was aware of the less than optimum power characteristics of this manifold. However for many other reasons this engine suits my needs for now. Also, I didn't see any comments on the power delivery with two throttle bodies...

From a practical point-of-view, the Lucas manifold compromises the arrangement of other components in the engine compartment. Ultimately I will probably fit a more exotic inlet set-up.

Dont go mad with the throttle size, as i suspect it will be horrible to drive round town - which is the last thing you want in a light car such as yours.

The throttle sizes were recommended by Jenvey. I'll be using 2 x 48mm.

Ian Mantula wrote:Thanks for the feedback Eliot.
Yes I was aware of the less than optimum power characteristics of this manifold. However for many other reasons this engine suits my needs for now. Also, I didn't see any comments on the power delivery with two throttle bodies...

From a practical point-of-view, the Lucas manifold compromises the arrangement of other components in the engine compartment. Ultimately I will probably fit a more exotic inlet set-up.

The inlet track area to each cylinder is smaller than the Lucas one. Which was designed for a 3.5 engine. Don't think adding an extra throttle body will help that.

Twin throttle bodes are for clearance reasons. The single large body and its mounting are far too bulky. The smaller bores may give better throttle response...

Ian Mantula wrote:Twin throttle bodes are for clearance reasons. The single large body and its mounting are far too bulky. The smaller bores may give better throttle response...

Obviously if the lower profile of the Thor suits your application, you have little choice. Keep us informed of how it goes, as it's an interesting and pretty unique conversion.

Can't say I've noticed any problems with throttle response in practice with the Lucas plenum, though.