Last month TRC showcased a brace of powerplants well suited to budget motorsport applications and Vauxhall's 1998cc C20XE 16-valve motor came right near the top of the list. With 150bhp and 144lb ft of torque as standard, tuners quickly realised the power potential of the C20XE, which could be readily unlocked affordably and reliably if carried out correctly. Even today the motor is very popular in a huge variety of motorsport disciplines from single-seaters, to Westfields, to MK2 Escort rally cars and track day Astras and Novas, where its reliable, torquey power delivery and affordable nature are much in demand. But how do you extract the best from this engine on a budget? To find out some answers, TRC paid a visit to one of the companies at the forefront of tuning the C20XE engine - SBD Motorsport Ltd to chat to its founder Steve Broughton.

What makes the C20XE engine so good?

Over to you Steve. "It's one of the last production engines with a massive in-built tolerance for being tuned up. Most of the components are good for 250bhp. The rods can cope with that - the only reason we advise against it is that if the engine is over-revved it can cause problems. Even the pistons are fantastic. The original piston is a forged item - it's beautiful."

The entire bottom end of the C20XE is very strong, especially the crankshaft. "It's bomb proof," says Steve. "I've never seen one break. Even with an engine has run out of oil and the con-rod has disappeared out ot the side of the block the crank is still in one piece!" Such strrength would be useless if the C20XE couldn't produce the power and torque to exploit it, but the cylinder head is something of a mass-produced masterpiece, being designed by Cosworth engineering for GM/Opel's requirements. Packing decent-sized valves and ports and a highly efficient combustion chamber shape, the alloy 16-valve head will flow enough air to reach 230bhp before modifications are required.

Symptoms of this problem are similar to those of head gasket failure - a film of oil in the water and a milky liquid in the sump - but curing it is difficult. some firms offer to bypass the gallery with external pipes, but Steve's not a fan of this as a cure, preferring to use only Coscast heads on his engines. these are identified by a lack of core plug style casting on either end of the head, plus they have an oval-shaped Coscast logo embossed onto the front. Finally, don't dismiss the very late engine that ran 'Ecotech' badging, because it may still be worth a punt. "The way to tell is the trademark L-shaped spark plug cover," say Steve. "If it's that shape it doesn't matter what's written on it, it's a C20XE/LN engine underneath."

Certainly the earlier distributor-equipped engine is the one to go for, because it's more likely to have a Cosworth head, plus the better bearing and pistons, even though it may have covered more miles. Interestingly, Steve reckons his ideal combination for an engine that he'd run in near standard trim would be to run an early crankshaft, in a later block (which was stronger), with a Coscast head.

General performance pointers on the C20XE and LN exhaust manifolds

So, how do you set about tuning C20XE and LN engines? Well, step number one is replacing the standard exhaust manifold, as the standard item was designed to maximise low-end torque. At high revs this becomes a restriction, so it's critical that it's upgraded at the earlist opportunity. Steve explains - "Apparently the first pre-production engines from Cosworth produced 170bhp as standard but they wanted more torque for the road which they got by making the manifold's pipes smaller. This also helped reduce emissions by keeping the gas speed up, but when you get up to the top end it becomes a restriction."

Happily, SBD has a huge range of manifolds for a wide variety of applications, whether front-wheel drive Astra, Westfield, Caterham or rear-wheel drive Escort or Manta. Prices range from £229.70 to £586.91 depending on applications, but if you don't attend to this early on, you're not going to produce the quoted power outputs as outlined here. Bear in mind that even on a standard engine a 6-8bhp gain can be expected when used with an efficient exhaust system.

Oil Systems

When the XE engine is used in front-wheel drive applications it's common to see the cars puffing smoke during hard cornering on circuit use. this looks worrying and can cause problems, as Steve explains. "There's a breather pipe coming out the front of the block which allows pressures between the top and bottom of the engine to be equalised. Sometimes on track use under heavy cornering the oil goes up that pipe and into the cam cover and it can't get out. This can detonate the engine where the oil mixes with the fuel in the cylinder head, but there's an easy modification to the baffle so that it dumps the oil back in again and cures the problem."

When the engine is transplanted into rear-wheel drive cars, more work is needed on the oil system - SBD advises using a hard-to-find Manta sump - while they produce a sump for the rear-wheel drive Sunbeam. "But if you can afford it, dry sumping is the way to go," says Steve, and that's certainly true when the motor is fitted into a Caterham, Westfield or similar. Expect to pay from £799.00 for this setup.

196bhp/170lb ft

Price: from £1767.15

MT196 Multi-throttle injection kit. This was the original twin throttle body kit developed by SBD in the mid 1990s as an upgrade for customers running Weber carbs. Featuring a pair of 45mm throttle bodies and an MBE 967EF ECU it gives a big upgrade at a price that's £300 cheaper than the taper throttle kits that superseded it on both packaging and power output. Peak power is around 6500rpm, but it'll happily rev much higher, which is why SBD advises fitting uprated con-rod bolts as a precautionary measure. "The standard rod bolts are really horrible, so we think it's a wise safety precaution to fit these," says Steve and the result is a bomb proof engine that produces a good spread or torque and power.

208bhp/172lb ft

Price: from £1915.49

TP 208 Taper throttle injection kit. For those with more to spend, SBD's most popular kit takes all the advantages of the MT196 a step further. Individual tapered throttle bodies (measuring just 66mm long and with a 45mm butterfly in the middle) allow more room around the inlet side of the engine, making this kit a viable proposition in just about any application. "It's just a straight bolt-on kit, plus the rod bolts," says Steve, so it's testimony to the brilliant design of the original engine that so much extra performance can be extracted from bolt-on tuning components. Peak power is again around 6500rpm, and the kit is designed to use Bosch Cream injectors as fitted to C20XE engine.

225bhp/172lb ft

Price: from £2934.96

Given that we're looking at budget horsepower, this is our cut-off point; beyond this stage tuning the C20XE & LN engines gets expensive. That said, between 225 and 230bhp allied to 177lb ft of torque is a lot of performace and it's produced by taking TP208 kit a stage further, adding a set of hydraulic cam profiles that add lift and duration. this extra valve lift requires pocketing the pistons, which gives customers a choice - they have SBD machine their original items or fit purpose-designed Omega piston. Fitting the Omegas helps keep the compressions up, which unleashes more torque and power, to the point where 230bhp is a distinct possibility. This also makes sense on a high-mileage engine, because the pistons can be used as part of a rebore. With TP225 the standard valve springs and caps replaced, while SBD includes a pair of vernier pulleys, to help get the cam timing spot on. The results: an engine that loses 8bhp at 2500rpm compared to TP208, but "after that gains torque and power everywhere and keeps going, peaking at 7200rpm and can rev to 7750rpm," says Steve.

For TRC readers on a reasonable budget that's probably as far as we would go; the next stage gets much pricier, according to Broughton. Even so, with up to 230bhp available, that's enough to make any road or motorsport car move in style!