@Count Iblis,
The 4.2 SC range rover versions do have a different exhaust manifold, from the outside it is a bit camouflaged, but the inside looks like a triple y system. That particular engine has some more changes that would suggest that it could deliver more hp, but Land rover iirc kept the jaguar performance specs in the sales brochures. But now my question, have you been involved in this manifold? Or do you know who has? It would be interesting to hear what the measured effects where.

 

The tri-Y or split log arrangement on the S/C engine, provided it is of sufficient sectional diameter for the volume throughput of exhuast gases will provide an appreciable gain, regardless of what power curve was claimed by Land Rover. The split log arrangement tends to favour low end torque most while lowering back pressure of the system will favour top end performance

 

ill take top end any day of the week well as long as Im not doin a tractor pull or such lol

 

"ill take top end any day of the week"
You really need more than 150 mph top end? Hope you have better chassis stability than mine has.

 

legend has it the R in standard form with the electronic limiter removed topped 200mph at MIRA, brave guy whoever did that!

 

Not top end meaning top speed you twit, TOP END aka the top of the RPM band 4000+ to redline which is what we are talking about here, the equal length headers will help in that area.

I am not one for trying to go 180mph

 

Now who is implying I would , 180mph is of course not on my list either.

But 300km/h is, and I think 310 km/h would probably be about the max with my gearbox/diff ratio/tire setup. Unfortunately this is not allowed on the relative safe oval tracks I know as I don't have a racing license, but I luckily I could try this on the public road towards the track in germany , if I could only overcome the fact that there are people waiting for me at home .

So for now it's only the enjoyment of top end power range as mentiojned by xjr-0220 in lower gears

 

amen brother AMEN^^^^^^^^^^^^^^^

 

Well, what you call top end power is NOT the only important parameter since the transmission is NOT continuously variable, and your engine is not always at top end. Peak dyno power at full rpm can only do good when the engine is running there. AND, unlike a Jaguar XJR, some tractor pullers DO have torque conversion that does alow the engine to run at the peak power point.

And, I hope the Europeans have more class than to even know what a tractor pull is!

 

No its not always in the top end but when Im racing I never drop below 4000 rpms so if I can make most my gains from something in the upper rpm band I will take that everytime as that will give me the most improvement in acceleration and 1/4 but I do have a nice cummins powered diesel that makes 670 hp and over 1000 rwtq if I want to play tractor hahaha

 

That's where the whole concept of downshifting comes in to play and all those gears in the transmission. You need higher rpm, downshift a gear or two and just like that, you're in top end power. The rpms don't fall below about 4k anyways during WOT acceleration.

 

X300 style vehicles are notoriously unstable at high speed.

I've taken a few XJRs to Nardo and on the autobahn

 

I don't know if I'd want all the top end on these motors since they seem prone to spinning rod bearings.

 

say, Adam. How did you determine that? There have been a few reports of that here, but they usually start with a question like "what happens if I find no oil on my dipstick?"

 

yeah these engines are not prone to spin bearings well unless not being taken care of properly.