Vintage Thing No.67 - Vixen-Imp Formula 4 hillclimber

Although I appreciate their engineering, I don’t usually like single seater racing cars because two seaters seem more sociable with a passenger to – er – entertain with one’s driving but I’m more than willing to make an exception with this device.

If you want a single seat vehicular conveyance you want a motorcycle, that's what you want. But I make an exception for this Vixen.

Look at that engine. That's a Hillman Imp engine, that is. And look at that gearbox. That's an Imp gearbox - up-side-down!

I’ve only ever seen a Vixen once before, many years ago at an Imp Club National, so imagine my surprise when one turned up at Wiscombe Park Hillclimb on 8th May 2010. It had so many features of constructional interest that I couldn’t stop photographing it in the paddock. Eventually my less than subtle activities came to attention of Penny and Andrew Coughlan, the owners and drivers, but this allowed me to ask them questions.

The Vixen was originally built in 1968 for the 1000cc Formula 4 racing. Formula 4 had originally been conceived as a formula for 250cc Villiers two-stroke engined cars but also saw 650 Triumph motorcycle powered racers before the Imp engine was accepted. In some ways it was like the Formula Junior of the early sixties and an alternative engine was the 997cc Ford Anglia engine as breathed upon by Cosworth, Holbay and other up and coming tuners. Most famous racer of the time was probably Bernard Unett who also raced Imps. The Ginetta G17 was a contemporary Imp-powered device with the same reversed Imp powertrain. Formula 4 began to fade in popularity in the mid-seventies but hasn’t stopped the cars being used for the occasional hillclimb.

The Vixen has a spaceframe chassis with wishbone suspension all round. The suspension uprights are special forgings and the brake discs are smaller than anything I’ve seen for a long time. Some Vixens had Hewland Mk9 gearboxes but this particular example has an inverted Imp box. This is what really grabbed my attention.

When as a callow youth I passed over my student grant cheque to a man suspiciously like Tim Millington in return for Wills ring heads and a 998 block at was then Talbot Special Tuning, the Tim Millington lookalike mentioned  a mid-engined Imp they’d once made with an upright Coventry Climax engine. If I remember correctly it was a 1216cc engine but I can’t recall what gearbox was used. The idea of a mid-engined Imp really appealed to me and still does as a callow middle aged man so I studied the Vixen’s drivetrain and gearchange linkage closely.

The box has to be inverted to overcome the problem of having one forward gear and four reverse gears if the gearbox is turned through 180 degrees. I am unclear what internal modifications had to be made. I imagine the lubrication system would have to modified in some way.

I was interested to see that ordinary Rotoflexes were being used. I remember asking Wayne Grimshaw about this at Tregrehan hillclimb because he used them on his Imp saloon. He reckoned a standard Rotoflex was easier on the diff and a she replaced them as a matter of course he’d never had one let go. Presumably, the Vixen is so light they aren’t so stressed. And without any bodywork their condition is more readily apparent.

The engine is mounted upright so that the carbs are now downdraught and the water pump is a standard Imp affair that looks curiously naked and slightly improper without its fan and shroud. I wish now that I’d paid more attention to how the mounting holes in both engine block and clutch bellhousing lined up.

The starter motor is mounted low down in a new position on the offside. You can just see the end of its shaft and spring behind the lower wishbone joint in the photo of the clutch slave cylinder. This lives right underneath the gearbox on a new bracket facing towards the rear of the car so that when you press the pedal it pulls the clutch release lever backwards. On a conventional Imp, it lives on top, faces forwards and pushes the arm forward, too. It’s such a mixed up, messed up world maybe the Vixen should be called Lola, ello, ello, Lola (cue air guitar).

This car was badly damaged at Werrington Hillclimb last year. Despite being there, some how I missed this and I’m glad I did. Penny clipped some dirt and the car darted into a stone wall, wiping off both the nearside wheels. Andrew pointed out a slight scuff at the bottom of the screen. “That’s where one of the front wheels just missed bouncing off her helmet,” he told me.

This doesn’t seem to have put her off much, though.

Looking at the car just over a year later you wouldn’t know it had brutally been turned into a two wheeler but talking to Andrew gave me an interesting insight into the importance of setting up such delicately balanced little cars. They managed to source a pair of brand new front uprights quite easily “from some guy up north” but instead of commissioning the re-manufacture of just one rear upright they had two made. They had some concerns about the gearbox because of the way the driveshaft had been mangled but this had escaped unscathed and was still performing.

I was too absorbed in all the rolling sculpture in the paddock to take much notice of the times that day but the Vixen easily held my interest just standing still.