The V8 Owners Forum -

What is the consensus of opinion on this.
I'd heard that the Range Rover 3.9 manifolds were better flowing than the 3.5, but i would expect those on the SD1 car to be better.

What about the later 4.6 manifolds. I know these may not be cast, but i am trying to avoid using tubular which in my opinion can create a lot of engine bay noise.
I'd rather listen to the aural notes coming from the exhaust.

I think 3.5 EFi and 3.9 EFi manifolds are the same - i.e. twin outlets. These are better than the single outlet earlier (carb) type.

The 4.6 tubular ones do have an acoustic shield on them as well.

Chris.

I have a set of 3.9's in good nick with all studs if you need some.

for my money the SD1 4-2-1 are the best of the cast jobs but they don't fit a lot as they are long. That said the best of any of the factory manifolds is probably the 4.6. This is just a assumption on my part as I imagine as time has moved they would have made a good job of them. IRC they aren't cast though but stainless. JE Engineering used to do big bore cast manifolds. I don't know if they still do.