Ok, I confess I haven't done a search through old threads in this one but wondered what opinions were on what works best, if there's any appreciable difference at all in exhaust manifolds??

I'm mid build on a refreshed 4.2 for my lse, nothing crazy but I have fitted over size valves and done some light porting work.
Reason for asking is I've always run it with original cast manifolds and home made de-cat one box system until now but I've inherited some stainless tubular headers , not sure of origin, not headman and are 4-1 with lambda bosses but they look a bit skinny on the primaries and to my mind at least the lack of any balance links or 4-2-1 doesn't make sense to me? I've done quite a lot of exhaust work on bikes, both mega revving multis and big singles & twins and i would have thought on a 'fairly' low revving rv8 that long primaries would lose low end response??
If anyone has experience with what works I'd appreciate some insight please

Exhaust manifolds make one of the biggest differences, but are often forgotten or ignored. This is vitally important on an n/a engine.

And the reason is exhaust scavenging. The aim here is to align the exhaust pulse from one cylinder, to pass the exhaust primary of another cylinder while the intake valve is open. This will significantly increase the density charge and promote a lot more power. Get this right and you'll see far more gains from the manifolds than the rest of the system, by a huge factor.

On something like a Corvette/Camaro with the LS1 engine, a good set of manifolds can be worth 30rwhp+. Which is a pretty significant gain. The old Rover V8 won't see the same numbers, but in relative terms (percentage) it will still be significant.

The biggest trouble is, for scavenging to work on an engine like the Rover V8, you need long primary pipes. The shorter the primary pipes, the higher the rpm scavenging will take place. In the tuning world these are usually referred to as either long tube or short tube headers. Short tube will still be much bigger than a stock log style manifold, but they won't promote scavenging until 7000-9000rpm+, which is not a lot of use for a V8 that only really revs to 5500-6000rpm max.

This is the reason you ideally want long tube headers, as scavenging will occur at an rpm range that suits the engine. Going bacxk to the LS1 example, a shorty header might make 5rwhp gain over stock, vs the 30+rwhp gain of a long tube header.

And herein lies the biggest problem. Very few long tube headers seem to exist for the RV8, especially for use in a Land Rover.

I run a Rover V8 in my Triumph TR7, luckily many years ago I bought a set of long tube headers for it, these were designed by a company called Triumph Tune and are essentially the same as what the works rally cars used to use in the late 70's, early 80's. They are huge and only just clear the chassis rails and extend under the car as far as the gearbox. Today companies like Rimmer Bros/Moss Europe and others don't sell headers like this. Which is a shame.

But they do make a difference to power and how the engine will rev.

So if you can find a set of long tube headers, go for it. Bang per buck as it were they are very good value for money. If all you can find are shorty headers, then they will still be better than stock, but they leave so much potential on the table.

Example of what a long tube and short tube look like:

Even though I'm not planning to upgrade my own RV8, I found your post both informative & interesting.

Thanks 300,
I don't doubt you as you seem to know your onions regarding v8's. I've done a lot of development work on race bikes and seen massive gains from properly developed systems, even on stock engines. we once worked out a link pipe for a stock race class 1000cc twin which gave an extra 25% in the midrange, made a good few quid selling them to the rest of the field
But I've never played with a v8 before...
By your description I have 'long' headers sat here although without further investigation they still seem a bit on the small side diameter wise and if I had the time to play with them I'd still be tempted to cut crossovers into them and see what happens.. I'll get the verniers on them soon!
Thanks again