The V8 Owners Forum -

I am fabricating my own exhaust manifolds, I am intending to make a system with 1 5/8 primaries, going 4 into 2 at two collectors, at the merge into 2 pipes the pipe will change into 2 inch pipe, then go past the bellhousing and then into a 2 into 1 merge, this merge will also go up to a 2 1/4 inch pipe for the rest of the system.

After the last set of merges the 2 1/4 pipes will meet at a X pipe somewhere under the transmission and then go back out to a pair of pipes to the back of the car.

The engine is only a 3.5 but i intend to fit a larger capacity Rover V8 in the future so am keen to build the system I need for the bigger engine rather than re-do all this again.

Obviously there will be two manifolds, a left and a right, the firing order is 1-8-4-3-6-5-7-2, is there a tried and tested pattern for pairing the merges ?

http://www.the289register.com/phpBB3/vi ... &start=105

and scroll down and go to page 9 too

Cheers
Pitschi

Hi
The ideal pairings are with cylinders fireing 360 degrees apart, then joining these pairs with pairs firing 180 apart, this ends up having to match pairs across banks (like a dual plane inlet manifold). The pairings are 1&6, 8&5, 4&7, 3&2 as you can see this is not easy on anything but a mid/ rear engined car.
Next best thing for the rover is 1&5, 3&7 off one bank and 8&2, 4&6. This is assuming long ish secondarys (around the same length as the primaries).
In current nascar practice you would join 1&3, 5&7 and 8&4, 6&2 with a much longer secondary than primary before joining the sided pairs. However I dont think you would ever ger the rover in a state of tune to take advantage of this set up.
Best regards
Mike

The Range Rover EFi manifolds (the ones with twin outlets) seem to have the following pairings:
1&5
3&7

2&4
6&8

Chris.

Many thanks for the advice, I will probably go with the 15 37 28 46 configuration.

I am undecided about primary lengths at the moment, I understand the fag packet rule of longer primaries give more torque so if this is true and not an old garage myth I want the make soemthing to get the best of both worlds.

Probably 12 inch primaries, around 14 to 18 for the secondaries depending on space.