Blydenstein’s 2400 “Straker”
BILL BLYDENSTEIN has a passionate belief in large capacity, four-cylinder engines. “By this means it is perfectly possible to achieve 4-litre performance with 2-litre economy,” he used to sav, ,tatement he has modified slightly as a sign of the times to “4-litre drivcability”. Inc tested his four-pot, performance/efficiency theory on Blvdenstein/DTV modified Vauxhalls many times over the years, in all sorts of vehicles from Gerry Marshall’s famous DTV racing Firenza “Old Nail”, then with 21/2-litre Vauxhall s.o.h.c. engine, to a bored and stroked, 2,170 cc. Cavalier Coupe with cam-in-head Opel-type engine. The latter was described in the September 1977 issue of MOTOR SPORT and at that tissue the Cavalier’s standard capacity was 1,897 c.c. Since then GM have bored out the standard VauxhaU/Opel engine to 1,979 c.c. (95 nun. x 69.8 sass.), which has inspired Blydenstein to stretch the iron-blocked engine even further, to 2,387 c.c.
Blydenstein offers this conversion as his “Strokes” kit, and though my so-equipped, Shepreth-modified test car happened to be a three-door Cavalier 2000 Sportshatch, which has replaced the Coupe in the Vauxhall model range, it is equally suitable for all the 2000 Cavalier and Carlton models and Opel equivalents. This legendary Vauxhall tuning specialist is not after outright performance. Indeed, the 0-60 m.p.h. times and maximum speeds are not vastly improved, even with the £150 optional gas.flowed cylinder head (with standard valves) attached to the test car. The real advantage lies in the area here extra urge is so much MOM meaningful to high average speed, low effort rilotoring, the 30 to 90 m.p.h. top gear acceleration bracket in which bags of torque is the criterion. The target was 30-90 m.p.h. acceleration in fourth gear of 25 sec. (the standard use takes 33-34 sec.) and 25 m.p.g.—plus overall fuel consumption, and this has been achieved. In fact my overall consumption of four-star worked out at an extremely good 27.6 m.p.g., including a good deal of cruising somewhat out of Blydenstein’s target range and some heavy city traffic work. The magic 30 plus m.p.g. touring consumption figure should be easily attainable if, as Blydenstein puts it, one drives “within sight of the speed limits”. Without the modified cylinder head, the “Stroker” conversion will knock the best part of a second off the 0-60 time, to just under 10 sec., but leave the maximum speed about the same as standard, at around 112 m.p.h. The modified head crops the acceleration times a shade further and adds a couple of m.p.h. at the top end. These figures are approximations because there was no opportunity to take accurate figures as I did with the old 2200 Coupe. That car was a good deal quicker, in fact (30-90 m.p.h. in 22.3 sec. and 0-60 m.p.h. in 8.7 sec.), thanks to Stage 2 cylinder head and a four-branch exhaust manifold. It was also thirstier, at 23.5 m.p.g. The “Stroker” conversion is a major operation involving a complete short engine rebuild. At the heart is a new, nitrided steel crankshaft which increases the stroke to 82 nun. from the standard 69.8 mm. The bores are bored and honed out to accept a set of 96.25 mm. (95 mm. standard) Cosworth forged solid skirt pistons mounted on a set of special, exchange, connecting rods. Somc
blocks require fettling to give adequate clearance round the crankshaft assembly. The pistons are slightly dished and retain the standard 9:1 compression ratio. As previously mentioned, the cylinder head can be modified if required. The ignition and carburetter settings remain as standard, so a “Stroker” engine should need no abnormal tuning and maintenance. In fact, if the optional Lumenition electronic ignition is fitted, maintenance requirements should be reduced. The kit is expensive. The crankshaft alone costs £595, plus another £270 for the Cosworth pistons, the connecting rods on exchange and a special thermostat. With access to the right boring and fetding equipment, a competent engineer owner could do the work himself, or farm it out to somebody with the ability and facilities. Alternatively, Blydenstein will carry out the conversion, at a cost of f100 labour for modifying the short engine and another £85 for engine installation and test. Balancing of the flywheel and pressure plate assembly on the crankshaft is recommended and included if Blydenstein do the work; it would be an added cost to the do-it-yourself man. With Lumenition ignition fitted, the total bill for a “Stroker” engine fitted at Blydenstein’s would be £1,088, with an option of another £150 for the modified cylinder head. All the prices quoted are without the 15% VAT. Bore tolerances are critical with the solid skirt pistons, so this is not a job to entrust to the back-street man with an ancient boring bar. Running in too is a critical process because of the tight piston clearances required, and when Blydenstein says that pressing the engine hard during running in might result in piston seizure, he really means it. Those expensive pistons’ solid skirt design is responsible for a somewhat disconcerting dcath-rattle every time the engine is started from cold, which gradually disappears as expansion overcomes the piston slap.
Most readers will surely agree that the standard Vauxhall/Opel Sportshatch is an extremely good-looking car. Blydenstein had made the test car’s design even more sportingly appealing with the addition of a DTV Sportpart front and rear spoiler kit. This costs £260 plus another £80 for fitting and painting, before VAT. Further improvements to the test car’s press-on characteristics came from a set of Bilstein “Comfort” gas-filled shock-absorbers (£26.17 each for the front, £27.45 each rear plus VAT) and modified springs. The Vauxhall Sportpart towbar kit, with which the test car was fitted, includes a pair of uprated rear springs. These had about % of a coil cut off them to lower the car, with a similar amount cut from the front coils. The test car’s automatic choke was erratic in operation, anus unusual trait of the standard
version of this engine and the aforementioned piston slap punctuated the first few minutes of cold running, but other than that this was an especially pleasing conversion. The sheer effortlessness impressed most, the lazy way it could be eased through city traffic with little gearchanging and then show off considerable top gear acceleration out on the open road, top gear acceleration faster than either a Rover 3500 SDI in fourth, or a Saab Turbo, Blydenstein claims, and those are high standards to judge by. The bottom limit in top is about 20 m.p.h., below which the usual GM transmission vibrations set in, but from that point on the big four will thump its way up the range in top gear in fine style. I say “thump”, and at lower revs it makes itself fairly obvious as a big four, yet in the mid ranges where it matters, this 2400 is smooth and unfussed. It grows fussier as the tachometer climbs towards she top of the scale, but that hardly matters, as to rev it hard loses the whole point of the mid-range torque advantage and wastes fuel. Like a big V8, the long-legged 2400 is relaxing to drive as well as deceptively fast in she higher gears, and that, plus an economy which no big engine of equivalent performance is likely to match, is what the Blydenstein philosophy is all about.
The handling is equally good and easy on effort, with not too much roll and excellent roadholding. Although the suspension modifications stiffen the ride and the seats are not very compliant, the overall comfort characteristics are sporting without being distressing. What might be considered more distressing is the cost of scan to the test vehicle’s admittedly optional full specification, which included modifications costing £1,973 including VAT. It would be £7,665 without the towbar (and this must make an excellent tow car) or spring modifications. But no four-seater car I can think of can combine such relaxed clriveability and top gear punch with relative economy. W. B. Blydenstein Ltd. can be found at Station Works, Shepreth near Royston, Herts. (Royston 60051)