D1 EFI manifolds and exhaust into One Ten V8 CSW

I'm after some advice.

My slidy-window One Ten V8 CSW is a lovely vehicle, but the engine lacks torque on hills. Compression etc checked out fine and it runs well. Since the exhaust Y-piece has been patched and will not last too much longer, I started down the famous path of: "while I'm in there I might as well upgrade..."

Some internet research revealed a good upgrade was to install some Disco 1 EFI 4-2-1 manifolds, RRC downpipes and Y-piece and a Td5 rear section. Allegedly it all bolts up, and seems a well-trodden path with good reviews. So I have bought the manifolds and Disco 1 V8 gearbox crossmember for clearance for the bigger pipes.

However, before I go further, I see there are auto (NTC7320) and manual (NTC7321) versions of the RRC downpipes/Y-piece kit. Probably because the auto gearbox requires additional clearance?

My question is, is there anyone on here who has done this and can advise whether I should use the auto or manual version of the downpipes/Y-piece to accommodate my LT95 gearbox? Does the LT95 need the additional clearance provided by the auto version of the pipes, and would it simply be safer to buy these? Or is there a reason to buy the manual version of the pipes.

Thank you for any insights.

I can’t advise on the pipes exactly. But I wouldn’t hold out too much hope for substantial gains.

What V8 are you running? Is it a low CR 3.5? If so that’ll be your issue.

Most petrol engines do their best work at mid or higher rpm. The low CR 3.5 is heavily strangled though. And while in the U.K. we might think of 3.5 as “big” displacement and a torquey V8. It is utter nonsense. It’s just the case the V8 made more torque than things like the 2.25 petrol or other even smaller displacement 4 cylinder engines back in the day.

The easiest gain for performance is to swap in a different engine. A 3.9 or 4.0 would be fine. But a 4.6 would be the best bang per buck upgrade.

As a side note the latter “Thor” 4.6 V8 actually make peak power at the red line. Again reinforcing that mid and higher rpm is where these engines do their best work. That said, there really is no replacement for displacement. And a 4.6 will make way more power and grunt low down than a 3.5 does.

As for exhaust tuning. With a naturally aspirated engine it is generally about a thing called scavenging rather than flow rate. Where the exhaust pulse from one cylinder creates a vacuum in another cylinder while that cylinder has its intake valve open. For this to happen you need long tube headers. The longer the primaries the lower the rpm the scavenging will take place. Google will give you an idea of what a long tube header looks like.

I’m not saying you won’t see some gains with what you propose but I’d suggest you’d be looking at more like 2-5hp. Although the old log style manifolds are not great at all. I’d suggest replacing the follows and maybe the cam though. The RV8 is known for wearing them.

Also worth noting that as a rule, tuning an NA engine moves the power curve to the right on a dyno plot. So gains normally happen at mid and higher rev ranges. Getting gains down low is much harder and normally requires boost or more displacement.

300bhp/ton said:

I can’t advise on the pipes exactly. But I wouldn’t hold out too much hope for substantial gains.

What V8 are you running? Is it a low CR 3.5? If so that’ll be your issue.

Most petrol engines do their best work at mid or higher rpm. The low CR 3.5 is heavily strangled though. And while in the U.K. we might think of 3.5 as “big” displacement and a torquey V8. It is utter nonsense. It’s just the case the V8 made more torque than things like the 2.25 petrol or other even smaller displacement 4 cylinder engines back in the day.

The easiest gain for performance is to swap in a different engine. A 3.9 or 4.0 would be fine. But a 4.6 would be the best bang per buck upgrade.

As a side note the latter “Thor” 4.6 V8 actually make peak power at the red line. Again reinforcing that mid and higher rpm is where these engines do their best work. That said, there really is no replacement for displacement. And a 4.6 will make way more power and grunt low down than a 3.5 does.

As for exhaust tuning. With a naturally aspirated engine it is generally about a thing called scavenging rather than flow rate. Where the exhaust pulse from one cylinder creates a vacuum in another cylinder while that cylinder has its intake valve open. For this to happen you need long tube headers. The longer the primaries the lower the rpm the scavenging will take place. Google will give you an idea of what a long tube header looks like.

I’m not saying you won’t see some gains with what you propose but I’d suggest you’d be looking at more like 2-5hp. Although the old log style manifolds are not great at all. I’d suggest replacing the follows and maybe the cam though. The RV8 is known for wearing them.

Also worth noting that as a rule, tuning an NA engine moves the power curve to the right on a dyno plot. So gains normally happen at mid and higher rev ranges. Getting gains down low is much harder and normally requires boost or more displacement.

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Thank you for your insights. I am aware most of the issue is down to the engine being a low compression 3.5L and it is never going to set the world on fire. I agree decent power really does require a different, higher compression, engine.

It is a nice original early CSW including original engine and I can't quite bring myself to swap out the engine - yet. My plan is to see if I can get an acceptable improvement (i.e. get up hills with not quite as much effort) without changing things too much. I've also got a 3.9L cam and new genuine lifters which I'll install in due course as apparently the 3.9L cam helps torque at lower revs. The Y-pipe and exhaust are on their way out anyway.

It should certainly improve it. If you want to tear into the engine then you can do a lot more of you are prepared to swap pistons and the like.

In an odd way Peak power is not always so different between the different Rover V8 displacements. The heads become a limiting factor at a certain level. But the bigger displacement will always give a broader power band.

If you want to throw some more at the 3.5. You can swap the crank and stoke the engine to 4.3 litres. Without changing the bore or block. And of course you could look at forced induction options. Quite a few supercharger and home brew turbo setups available these days if you want to play around.

Something else to look at is gearing. I can’t recall what the 110 has. We have a C plate (1985) factory Ninety V8. In the Ninety it has the 5 speed Santana LT-85 it also has a very tall 1.192:1 transfer box. Giving it very tall gearing compared to say a 300Tdi or Td5 Defender.

We haven’t changed this yet, but swapping in say a 1.4:1 transfer box would likely really wake it up. Downside will be higher cruising rpm. But I personally don’t think it would be too bad as the diesels would cruise at the same rpm anyway.

In the Ninety it had a 3.5 running on twin Stromberg carbs. It was smooth and didn’t go too bad. But was a bit gutless in 5th and a good Tdi would out perform it. A couple of years we swapped in a 3.9 EFI using the 14CUX ECU. This engine could do with some work too, it’s completely stock and I’m sure the cam/followers need doing. But even so the torque increase is very noticeable. Despite the tall gearing it’ll now pootle around in 5th at under 30mph and be able to take you to over 80mph with relative ease.

Thank you for the comprehensive information, much appreciated.