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.