The slim and compact eight-valve Vauxhall engine has been the hero of many a Nova, Cavalier and Astra. Find out here how to optimise its tuning potential.
WORDS Rob Hawkins
PHOTO David Wigmore, Rob Hawkins
Vauxhall’s single overhead camshaft, eight-valve engine has often been left in the shadow of the more powerful twin cam XE. Yet its compact construction, light aluminium cylinder head and tuning capabilities have seen some impressive results. With full race engines producing 200bhp and even the standard 2-litre being capable of 130bhp, such figures can raise an eyebrow, even by modern standards.
The first of the eight-valve engines appeared in 1981. Models such as the Nova, Corsa, Astra, Manta and Cavalier have all sported such an engine. It was fitted to the Corsa up to 1998 and even later in the 1.6 MkIV Astra. Performance models such as the Astra GTE and Cavalier SRi gained an excellent reputation thanks to its single overhead cam configuration, cast iron block and aluminium head.
The Vauxhall eight-valve is available in a variety of sizes, ranging from the 1.2, 1.3 and 1.4-litre engines up to the 1.6, 1.8 and 2-litre units. They’re cheap to buy, because everyone wants a twin cam and straightforward to modify. There are plenty of bolt-on modifications, ranging from induction kits to exhaust systems and performance carburettors. Specialists such as B&J Engineering know how to modify the internals including boring the blocks, gas-flowing the cylinder head and fitting larger valves.
Outside the Vauxhall model fraternity, the eight-valve is a popular transplant and slots comfortably into kit cars such as the Westfield, and CC Cyclone. The autograss scene uses it in specials with overbored 1420cc units producing 150bhp and revving to a healthy 8000rpm.
The cost of modifying an eight-valve is similar to most NA 4-pots and the performance gains are worth the expense. We’ve produced a separate table outlining what you get for your money. Typical induction, fuelling and exhaust modifications will produce up to 20bhp extra output. A performance camshaft and some headwork can see an additional 20bhp.
Over the following pages, we’ve outlined some of the popular tuning upgrades available for the eight-valve Vauxhall engine. Read on to find out more...
• EXHAUST UPGRADES
Starting at the exhaust manifold, the smaller eight-valve engines perform better with a 4-2-1 system. Manufacturers like Sportex produce such a manifold, which is stocked by specialists including Online AutoSport. Prices start at £109.
Ashley produces a performance exhaust manifold for the Astra GTE, Cavalier SRi and Nova SR and SRi. Available through their site, prices start at £198.
The larger 1.8 and 2-litre engines are sometimes said to perform better with a 4-into-1 manifold. Specialists such as Tony Law can manufacture these for around £400.
• OTHER ENGINE INFO
The 1.8E found in MkI Astra GTEs, early MkII GTEs, and Cavalier SRis is actually one of the best big block eight-valvers from a tuning point of view. It has a twin butterfly throttle body with approx 60 percent more surface area than a 1.8SE/2.0NE/2.0SEH single one. The inlet runners are shorter on the 1.8E manifold, the inlet ports are 3mm wider and are shorter on the 1.8E head, the combustion chamber is the same size as the 1.8SE/2.0NE/2.0SEH so it doesn’t effect the compression ratio and the valves are the same size.
Fitting the head to a 2.0NE/SEH, is basically the same as boring the 1.8 block to 2.0, the extra power coming from the extra cc. Fitting a 1.8E head/inlet to a stock 2.0 bottom end is supposed to make a big difference to throttle response (we’ve never actually seen this done to comment). It’s reckoned the gains of a 1.8E head would show more on a more modified engine, that could make more use of the extra flow capacity of the 1.8E head/inlet. Maybe by using a modded 16-valve bottom end. Cheers to John at mk2cav.com for this info. The SEH was the ultimate incarnation of the Vauxhall eight-valve and was found in the MkII Cavalier SRi130 and MkIII SRi.
A slightly different version called the SE with 122bhp was fitted to the Astra GTE and Carlton. This is the list of modifications done to the 2.0 eight-valve to change it from a 113bhp NE to the SEH: 2-inch exhaust with straight-through silencers, revised Bosch Motronic engine management, larger intake valves and exhaust manifold, more compact combustion chamber shape, shorter, lighter pistons, revised valve timing, integrated, adaptive engine management and ignition system engine block both stiffer and lighter, crank and con rods lightened, friction loss cut by thinner piston rings and valve stems, new high efficiency oil pump and cooler in front grille, smaller water jacket for quicker warm up and enhanced pump. Standard: 128bhp at 5600 and 133 lbf/ft at 4600 rpm.
• INDUCTION AND FUELLING
A vast assortment of replacement air filters and induction kits are available from the likes of K&N, Pipercross and Green. These promise better breathing and a more responsive throttle. Websites such as Demon Tweeks provide an online search of filters and induction kits for particular models of Vauxhall.
Non-injection engines were usually fitted with GM’s Varajet carburettor or a twin choke Pierburg unit. Carburettor engines can be easily modified with a pair of side-draught Weber or Dell’Orto units. Second-hand 40mm carburettors can be bought at autojumbles and eBay for around £150-£300. An inlet manifold costs £200 from Bogg Brothers.
An alternative to twin carburettors is a full set of motorbike carbs. Specialists such as Bogg Brothers can supply a set of used and guaranteed 40mm Yamaha R1 carbs and a suitable manifold for £330 plus postage. A drive in, drive out service can be had from £800. (including parts). The benefits of bike carbs includes no flat spots, better fuel economy and a little more power over twin carbs.
Top of the range for the eight-valve has got to be throttle bodies. Budget for upwards of £1000 for a full set including inlet manifold from manufacturers such as SBD Developments. However, you’ll also need an aftermarket ECU (eg MBE, Omex, DTA) to control the throttle bodies. These will cost around £700.
• BLOCKS AND BOXES
There are a number of gearboxes supplied with eight-valve engines. As a rule, on big block engines, the F16 supplied with the engine will be fine but you can upgrade to an F20 or F28 if you want, these require extra modification to fit though, on cars such as the MkII Cavalier. There are quite a few different ratio F16 boxes so make sure you know which one you have/need — the same goes for the F13 and F15 ’boxes supplied with the small block motors.
The cast iron engine block uses the same bore centre for the 1.2, 1.3, 1.4 and 1.6-litre engines. Early 1.6, 1.8 and 2-litre engines use the same block.
Internal modifications to these engines are available with parts such as Arrow con rods and Omega pistons. However, an engine swap for a standard unit with greater cc is often cheaper and more effective. Some engine swaps are not so straightforward. Slotting a 2.0 into a 1.2 Nova or Corsa requires modifications including brake and suspension upgrades.
• CAM OPTIONS
A single overhead camshaft set-up operates eight single sprung valves with hydraulic tappets. Camshafts from the likes of Piper and Kent are available with an assortment of profiles for under £250. A Vernier pulley is worth fitting with a performance camshaft for fine tuning of the timing and will cost around £100. Highly modified or competition engines can be uprated with double valve springs and solid lifters, available from companies such as B&J Engineering.
• FACTS AND FIGURES
A Uprated oil pressure relief valve kit costs around £60 from B&J Engineering.
B Flat-sided oil pump drive on the left can wear, but B&J Engineering supply a stronger steel version. Six-sided drive on right is better, but these parts are not interchangeable.
C Some smaller engines have baffled sumps as standard. Non-baffled sumps can be modified.
• HEAD MODS
All eight-valve engines use an aluminium, eight-port, crossflow cylinder head. Inlet ports on early 1.4 and 1.6-litre engines and all 1.3-litre units are D-shaped. Later engines, including multi-point injection units, have round inlet ports, which are better for a modified engine because the inlet tract has a straighter flow to the valve.
Cleaning up the ports helps to increase performance. Larger valves are also available. For the smaller 1.2-litre up to the 1.6, increase the exhaust valve size by 1mm (don’t change the inlet valve). On the larger 1.8 and 2-litre engines, both the exhaust and inlet valves can be increased by 1mm.
The compression ratio of the cylinder head can be increased, but only by changing the pistons. The shallow combustion chamber on the eight-valve’s head restricts modifications. The standard dished pistons can be changed for flat top ones, though tracking them down is getting harder.
The 1.3 and 1.4-litre engines shouldn’t exceed a compression ratio of 12.8:1, whereas the 2-litre can take a lower 12:1.
Fitting a larger engined head onto a smaller-engined block won’t give you any performance increases. Instead, the compression ratio will be lowered, which will in turn reduce the overall performance.
EIGHT VALVE SPECIALISTS
B&J Racing Engines
0161 748 8663
Bogg Brothers LTD (bike carbs and sump mods)
Ashley Competition Exhausts
Tony Law Exhausts
Vauxhall Performance Spares Centre