Vauxhall Blydenstein Chevette 1500

Introduction

THE FORMULA of putting a big engine in small car was not new - that the car was a Chevette was, however, a little adventerous. It would also allow the engine to achieve its most efficient speed, that at which it developed optimum BMEP (Brake-Mean Effective Pressure). At this speed, improvements in efficiency resulting from minor changes to the engine's specification could best be measured for judgement of improvement or loss.

Therefore, any improvement in BMEP could often be associated with a change in the relationship of bore/stroke ratio. In the case of Bill Blydenstein's Chevette, much of the gains that had been made could be traced back to the longer-stroke crankshaft with which the car was fitted. However, there were very real limits to which the stroke could be taken in an engine of pre-set size.

Thus, in the "big capacity" Chevette, a realistic ratio of 1.14 was retained despite increasing the bore as well as increasing the stroke. This compared with 1.36 for the standard engine which was already well over-square with a resultant reputation for longevity that a low piston speed usually brought. The increase in stroke was accoplished by use of a steel cranksha built up by Gordon Alien who also produced the very short connectin rods.

Increasing The Stroke

1,483 c.c. would have come about by increasing the stroke from 61 to 72mm, but the only suitable piston with enough skirt were Hepwort Powermax ones with a width of 81.75 mm. These were therefore specified, requiring an increase in bore from 81 to 81.75 mm giving the final capacity of 1,511 c.c. Other Blydenstein improvements included a DTV Stage 2 cylinder head and Lumenition electronic ignition. These modifications gave an increase in power at the rear wheels of around 18 to 20 hp, the relevant figures being 42 hp at 90 mph for a standard Chevette and 60/62 bhp at 80 mph for the Chevette 1500.

Better still, the maximum power of the bigger-engined Chevette occcured at only 5,000 rpm, while the smaller capacity "standard" engine developed its maximum power at 5,600 rpm. Since the BIydenstein Chevette was capable of maximum speed of around 98 mph, it was seriously under-geared as the top speed was equivant to an engine speed of 6,160 rpm. We do not know if any were converted, but the Viva 1800 3.73 or even the 3.45-to-1 axle om the Magnum 2300 models would have seemed to be a better match given the increase in power - and it would have likely given the 1500 a top speed over the magic ton. But as it was, the Blydenstein Chevette would leave the driver in no doubt that the engine was working hard at high revs.

Why Make A Performance Chevette?

We have no idea who made the decision to create a "hot" Chevette - it may well have been Bill Blydenstein himself. The choice of car may seem strange, but the Chevette did offer excellent steering and roadholding, and road testers of the standard iteration had often declared that the chassis deserved more power (not all thought this, however). But those who did drive the 1500 would soon discover a car capable of accelerating from rest to 60 mph in 11.4 seconds and to 80 mph in 22.7 sec. But in terms of useable perforance on the road, it was the acceleration in the gears that gave the most valuable information. The Blydenstein Chevetfe's ability to accelerate from 50 to 70 mph in top gear in just 9.5 seconds put it in the league of such notable "performance" cars as the BMW 320i.

Blydenstein Power

As was the case with most other Vauxhall's of the era, the 1500 demonstrated a lack of refinement when accelerating from very low speeds, and it was not really happy when asked to run at less than 25 mph in top gear. Some road tests suggest it would boom and rattle when accelerating from under 1,500 rpm in any gear under full throttle - not acceptable by today's standards, but not such a big issue in the mid 1970's.

And being born into the petrol crisis, economy was always an important factor. Here, the Blydenstein 1500 could achieve around 37 mpg on the highway, although if you sank the foot this could fall as low as 24 mpg.

Externally, the car was equipped with a deep front spoiler and neat moulded plastic rear lip, both of which added nothing to the performance, but they did greatly improve the appearance of the Chevette. Apart from these and the "Blydenstein Power" decal the car was as standard. Under the hood, apart from the Lumenition electronic ignition wiring by the distributor, the engine looked much like the standard issue.

Ride and Handling

Undoubtedly the worst feature of the Chevette was the poor low and medium speed ride. It was harsh and jolty through spring rates chosen for a good laden ride. Vauxhall needed only to look at the Opel City, for example, to see how progressive rate springs could counter this problem and have a superior unladen ride as a result. But apart from the harsh ride, there was absolutely nothing wrong with the handling and roadholding. Balanced handling allied to good suspension control and quick steering gave the Chevette's driver refreshing reassurance and the speeds and attitudes that the car could be thrown around at were remarkable.

As a logical successor to such peers as the Mini-Cooper S and Escort Mexico, the 1500 Chevette for little over £2,000 should have created a whole new cult of its own. It had few natural rivals (certainly not at its price) and only the Volkswagen Golf 1600 LS seemed to approach the small dimensions and high performance - and the Golf costs nearly £400 more (RRP pricing as at 1976). Many believed the increased engine capacity would overstress the driveline, but from the reviews we have read we can find no evidence to support this theory. The standard brakes and suspension were also good (for the time) and were certainly up to the task. But there were a few issues. The seats offered inadequate lateral support and inside there was a lack of instruments you would expect in a performance car - no rev counter or even an oil pressure gauge made the car appear cheap.

Sure, the deep bib spoiler did hang some three inches lower than the vestigial lip that all Chevettes had below the normal front valance - and that gave the car a performance look (and maybe it improves straight line stability while reducing what little natural understeer there was at high speed). But most would have liked to "see" the performance from inside, courtesy of a rev counter. The Blydenstein conversions were carried out at Shepreth, and the company worked out the relevant exchange prices whether the customer supplied their own short engine or had the work done on the engine in their own car.

Quick Specs:

• MANUFACTURERS: Allen Tool and Eng. Ltd. 271, Argyll Avenue, Trading Estate, Slough, Bucks, W.B. Blydenstein Ltd. Station Works, Shepreth, Nr. Royston, Herts.
• Engine: ln-Iine 4 cyl 82 x 72mm 3:23 x 2.83 in., 1,511 c.c. (92.9 cu. in.); Stromberg 150 CD carb. 77 bhp (DIN) at 5.000 rpm (The heart of the conversion was the special steel crankshaft, short connecting rods and Hepworth Powermax pistons, built up by Gordon Allen)
• Consumption: Overall mpg: 32.9 (8.6 Iitres/100 km).
• Transmission: Front engine, rear drive. Manual overall ratios 4,11. 5.75, 9.08, 14.22, rev 15.24, Top gear mph/1,000 rpm: 15.9
• Suspension: IFS unequal length wishbone, coil springs, anti-roll bar. Rear, live axle, 4-link top and bottom trailing arms, Panhard rod, coil springs; telescopic dampers.
• Steering: Rack and pinion. Turning circle 30ft 10in. (9.4m).
• Brakes: Dual line, hydraulic with servo assist., front discs 9.4 in. dia., rear drums 8 x 1¼in.
• Dimension: Wheelbase, 94¼in, (239 cm.): front track 51½in. (131 cm.): rear track 51½in, (131 cm.): Overall length 12ft 11¼in. (394 cm): width 5ft 5 ¾in., (166 cm). height 4ft. 4 in, (132 crn.). Unladen weight 16.6 cwt (846 kg). Max payload 1.063 lb. (483 kg)
• Tyres: 155SR 13in
• Fuel: 8V2 galls (38,6 litres)
• Conversion cost: inc, Stage II DTV head, Lumenition and spoilers £756