Xpit F4 (Formula Four)

[Tedd]

Asking US$5,000 obo.

Formula Four is a class for cars powered by 750 cc motorcycle engines (850 cc for 2-valve engines) -- like an early version of F1000. The Xpit was designed in Ontario in 1972 by Eric Siegrist, and this example was built by Eric Siegrist and Stu Lamont, probably around 1974. It's powered by a first-generation Honda CB750 SOHC.

The Chassis
The car is currently being run as raced in the mid 70s, without wings. However, it has been raced in a more modern configuration, with a GSXR-750 engine and wings. The wings are included.

The Powertrain
While essentially stock in configuration, the CB750 engine has numerous upgrades that improve reliability and, to a lesser extent, performance.

• Balanced crankshaft
• Forged Carrillo connecting rods
• Reinforced rocker cover (rocker tower braces) as used on factory Honda race engines
• Modified float bowl sumps (for operation under lateral G)

In addition, the deal includes the following components that could be assembled into a much more powerful (but still F-Four legal) engine.

• Hilborn mechanical fuel injection system (with pump)
• 836 cc kit (larger-bore cylinder barrel and matching pistons)
• Ported cylinder head with enlarged valves

Because of the large number of CB750s made, engine and transmission components are readily available from Honda dealers or online sources such as Bike Bandit and Vintage CB750. Compared to most, this is a very easy vintage car to keep track-ready.

Miscellaneous Components
A large number of spares and related components are included.

• Front and rear wings (not currently being used, but fully functional)
• Side cooling inlets
• Rear lower A-arms
• Rear uprights
• Many Honda components (cylinder heads, starter motors, clutch components, transmission bearings, etc.)
• Drive sprockets of various sizes
• A second set of rims, with rain tires mounted

In addition, critical chassis dimensions and most custom components have been modeled in 3D CAD, facilitating their re-fabrication should that be required.

[Jnovak]

Ok all you wannabe racers. These are fabulous little race cars. I went to Canada to talk to Eric and he was kind enough to show me EVERYTHING. A brilliant car for the time for sure.

I am tempted just to be able to say that I owned an Xpit!

These cars are what made be become a Racecar designer and builder. Thanks Eric!

[Ty_Handke_83]

If it wasn't on the other side of the country...

[Jnovak]

If it wasn't on the other side of the country...

Ship it. Fabulous Racecar.

[Ty_Handke_83]

Ship it. Fabulous Racecar.

I'm quite a sizable chap... have issues fitting into most cars. I've looked at the ones that run locally, and figure it would be a squeeze.

[Tedd]

Ty:

I'm sure we could deal with the distance issue. But you're right, size is a bigger problem because the cockpit is fairly narrow. The car can accommodate quite a tall driver, I'm sure. I'm 5'8" and I have the seat in the full-forward position. But thigh, hip, and shoulder width is somewhat limited.

Jay:

I'd always loved the F4 cars, too, which is why I bought this car. When I used to race in Ontario years ago I thought about building one, and I probably would have if I'd stayed in racing back then. When I decided to get back into it a few years ago, in vintage, this car came up and I knew I had to have it.

It's quite sophisticated for a car of its era: TIG welded chassis; chrome-moly suspension; and stressed engine with the chassis splitting behind the roll hoop. It's also a lot of fun to race. Not as quick as an FF, but it probably could be if I put the high-performance version of the engine together.

Tedd

[rickb99]

THIS is close to the old Formula 3 cars as run post WWII ! But using 750 cc instead of 500cc. This is what the 1950's and pre war Formula One drivers started in..

[Jnovak]

THIS is close to the old Formula 3 cars as run post WWII ! But using 750 cc instead of 500cc. This is what the 1950's and pre war Formula One drivers started in..

Actually these cars are MUCH more sophisticated than the 50s F3 cars.

[Tedd]

Rick is probably thinking in more general terms -- motorcycle engine with rear mid-engine configuration -- like Stirling Moss's Cooper-JAP of the early 50s. But, yes, by the 70s the cars were a lot more sophisticated than that. This car is as modern as any small formula car up to about the end of the 70s.

What I've been told is that the class started as Austin Seven racing in the pre WWII era. The cars gradually morphed into open wheel cars (exactly the way American sprint and midget cars evolved from the frame-body-fender road cars of their day). Eventually, they were pure formula cars, by which time it started to make more sense to use motorcycle engines than car-based 750 cc engines.

Tedd

[provamo]

i recall running against the previous generation of these cars in Canada in the early seventies, they reminded me of then contemporary Formula One cars but scaled down
twin opposed cylinder BMW powerplants were popular then

an amazing car and PRICE!

[marshall9]

I like it !

[Retroracer]

History of the class is here:
http://www.formulafour.com/history.htm

[Tedd]

an amazing car and PRICE!

It's also a very economical car to race. Drivetrain parts are readily available and inexpensive. And, being a Honda, the engine-gearbox is very reliable. I've made a few tweaks to make it happier at sustained high RPM, and now it's basically a roll-it-off-the-trailer-and-go-racing kind of car. Being so light (635 lb dry weight) it's very easy on things like tires, brake pads, and rod ends. I replace the pads every season, but I don't actually have to. I buy the softest compound Hoosier makes -- used -- and they last all season without much loss of performance. In fact, last year I set my fastest lap ever at Mission on the last day of the year. I doubt anybody road races for much less money than I spend, but the car is as much fun to drive as an FV and almost as much fun as an FF.

Tedd

[rickb99]

Classis F3 racing of old. And yes, when there wasn't a formula one race you could find the likes of Fangio, Ascari, Moss, Bandini, Behra, etc running F2 and F3 races. F3 was the training ground.

THE REAL F3 RACING as it was:

https://www.youtube.com/watch?v=02Tq_gaPPbM

[twofoot65]

Ted, I've sent you a couple of emails and not heard back. Is the car sold?

Thx

Chris

[Tedd]

Chris:

I'm just replying to your email now.

Tedd

[devin.hanes]

This is what the car looked like originally in 1979 & 1980
(Car #152: the "lead" car in both photos.....)

scan0001-001.JPG

1980-Mosport-F4.jpg

[Earley Motorsports]

Is there a class for these or more modern versions in the states? Haven't seen any run.

[Jnovak]

Is there a class for these or more modern versions in the states? Haven't seen any run.

Not to my knowledge. The closest class would be an F500 with an MC engine. However the fastest F500 with either type of engine are much faster than the F4 times. This conclusion is based on lap times at Waterford for the F4 cars.

I would suspect that if someone built a really modern F4 with a modern 750cc engine it would be a rocket ship about as fast as an FC car.

[rocketeer174]

Jim Morton and Bob Long are running around the 1:25.5 around Mosport (Canadian Tire Motorsport Park).

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[rocketeer174]

A f2000 car runs about 1:21 and a f1600 around a 1:29.3

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