Romper Stomper

Cars and Car Conversions (remember them?) were interested in the ACT products and their effect on the Rover V8 performance. In April 1999 2 TVR 420 SEACs were put through their paces by Dave Walker of CCC on a test track near the M3.

Both cars have the Rover V8 engines with one engine being a 4.6 and the other a well tuned 4.2.

On this page you can read what Dave Walker told the readership of CCC.

Kind permission of Cars & Car Conversions

I have to confess that the Rover V8 is one engine that has always puzzled me. We see a lot of them on the rolling road and seldom do they give the power that the owner is expecting. Often as not, big 4.6-litre engines make masses of torque but with no top end. About the only exception to date was the engine in Lee Parks’ TR7 V8, which made around 180bhp at 7000rpm.

Enter Tim Lamont with his carbon intake system for the Rover V8 engine. Tim runs a company specialising in parts for the Rover V8. The company is called ACT Performance Products and Tim would like it known that he does this on a part-time basis – more as a TVR enthusiast than anything else. Tim’s main job is as a model maker and prototype manufacturer.

Tim runs a TVR 420 SEAC and, over a period of time, has used this engine to develop his own induction system. In order to fabricate his system in carbon-fibre, Tim even built his own autoclave! There are basically three advantages in working with carbon-fibre. First of all, it’s very light; secondly, it’s an excellent heat insulator; thirdly, it looks very fast (that’s the bit we like – Ed).

The stock Rover induction system comprises an inlet manifold, a top section containing induction trumpets and a plenum lid which houses the throttle body. The inlet trumpets look different lengths but, due to the way they cross over internally (and when you take manifold and port length into account), they actually work out the same. A hose then connects the throttle body to the air metering flap. In the case of the 420 SEAC, this metering flap is not the stock Rover item but the larger Jaguar unit that the TVR factory fitted on the SEAC models.

The 4.2-litre engine came with fully ported heads, to which Tim has added a 234 camshaft and a well-developed exhaust system. Normally, this engine runs Tim’s own induction system but when it arrived at the Emerald workshops, it was sporting the standard set-up so we could run a base figure for comparison. However, the inlet manifold was not standard, but opened up to 45mm to take the larger carbon induction system. It was really just too much trouble to be changing manifolds for our back-to-back test, so the stock system had the added benefit of a larger-bore, ported inlet manifold.

The base line figure really gave me some food for thought. 299 BHP is a hell of a whack for a road going 4.2 litre Rover V8. Okay, it was very cold in the workshop and with temperature correction this dropped to 290BHP, but it’s still a lot more grunt than we normally see from fast-road Rover V8s. Average for a fast-road conversion is 230 to 250BHP, while Steve Lyall’s Clinic TVR barely made 200bhp.

Now we could add the Tim Lamont carbon intake system. The inlet manifold can remain stock, but to get the best from the system Tim opens up the intake to 45mm diameter (38mm standard) and fits matching 45mm intake trumpets. These are shorter than standard and open up to 50mm at the intake end. The carbon lid that goes over this lot has 50 per cent more volume than standard, and takes a much larger bore throttle body.

The design of the lid was aided and abetted by Tim Watson – a man who works with wind tunnels for a living – and the internals shaped to get the air into the engine in the most efficient manner possible. The throttle body has a 76mm butterfly, and the butterfly is tear-drop shaped for aerodynamic perfection (probably gilding the lily a little, but it does the trick). A new, larger-bore hose connects this lot to the air metering flap.

On the rolling road, I take careful note of the oil and water temperature readings and start each run from the same bas position. I also know the rollers (well, they are mine) and I’m really confident that Tim’s induction system works. We saw 310bhp observed (corrected to 301bhp), a gain of 11bhp over the original figure. But that isn’t the whole story. You gain torque just about everywhere.

Given that the ‘standard’ bas run wasn’t with a standard inlet manifold but an enlarged and ported one, the gains are very impressive. The fact that you get additional torque across the rev range can’t all be due to breathing restriction. Tim’s trumpets are a different length from stock and the pulse-tuning effect has to have played a major part in the power gain.