Good though Old Nail was, after a couple of years the 'fastest tractor engine in Europe' didn't have the grunt to stick with the wilder V8 engined special saloons; more power was needed. Vauxhall were planning a V8 Ventora road car for 1975, so DTV decided to use the FE shell for their first purpose built Super Saloon.
The new car used a 476 bhp Repco-Holden V8, driving through a Borg-Warner T10 gearbox to a 3.5:1 Salisbury Powrlok diff. Suspension was double wishbone at the front, with a De Dion axle at the rear; brakes were from AP racing, and wheels were 12 x 15 front, 15 x 15 rear.
The Ventora, christened Big Bertha by Marshall, first appeared on the Vauxhall stand at the Motor Show. Half race car, half heavy show car with fettled bodywork and perfect shuts, it was always too much of a compromise. Though it won three races out of six, when it waltzed heavily into the Armco at Silverstone having shed a set of brake pads (fortunately without injuring anyone) there was a feeling it was for the best. By then Vauxhall had dropped the V8 road car because of the fuel crisis; freed from marketing constraints, DTV could use the best bits of the Ventora in a design of their choice. The result was Baby Bertha.
John Taylor came up with a way out caricature of a Magnum coupe and the team set to work, creating a rigid backbone chassis which used Big Bertha's De Dion rear with inboard rocker front suspension by Frank Costin. DTV's fibreglassers turned Taylor's sketch into sleek, squared off reality around a Firenza centre section, holes punched everywhere to keep engine, brakes and Marshall cool. Baby Bertha was right straight out of the box, 'a super, super car', winning the '75 and '76 Super Saloon championships and still holding four lap records at the end of '77.
With the Firenza obsolete, a replacement was needed from the new Vauxhall line up. The Cavalier Coupe was chosen and Mega Bertha was born, with a glassfibre shell wider by a foot than the road car, sitting on a Formula style racing car chassis. Power was originally to be a turbo slant four, until contacts in GM sourced a supply of the 8.1 litre aluminium Reynolds-Chevrolet V8 - good for 700 bhp!
By then, though, Vauxhall's interest had turned to international results in Group 1 and production cars. There was a feeling that DTV had done all they could in British club racing and that to run such a car was overkill. When the Chevette HS project began it was clear all Shepreth's effort would be needed in rallying, and Mega Bertha was abandoned.
Baby Bertha survives to this day, occasionally seen at events like Goodwood Festival of Speed; Mega Bertha was in Ireland, but was purchased by Ric Wood and finished to a high specification (more information on Ric's web site), and has appeared at Goodwood and other meetings. What was left of Big Bertha sat at the back of the Shepreth workshops for several years before being sold off; it has never been seen since.