The birth of 2306

After trying a 458 and a Mp12 and finding them too bland on road, and possibly ruinous to run on track decided to do the build your own car.

Settled on a superformance GT40, basicaly a new build of the old 60s car, same tub etc, just better brakes, shocks and tires.

Take one 302 SBF, worked to give 575hp and mix with a hybrid english american chassis, german transaxle, 2400lbs and you have the quintisential viceral track machine.

Realtively simple to keep and run, as fast as a modern street based car if you are preppared to work for your speed. The downside is it makes an elsie seem refined, its all about mechanical grip. Its admittedly a bit much for the street, being really really sharp and quick to react, you cant really see backwards well, and too much power for poolting about.

On track its like a giant elise, heavier at the controls, and one has to learn how to really modulate, there is always more power, it all happens very quickly, and even on the straights no time to relax so epic is the rate at which speed builds. Lots to learn.
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Its an interesting and very entertaining drive, more grip than the elise, twichy but controlable when it lets go.

On a number of corners where I hit the rumble strip which made the lotus fast, here the power flow is so intense that the tire on the rumble spins on the smooth paint.

So far the rev limiter is set at 5800, but we know from the motor build and dyno test power peak is at 7100, so long way to go yet.

I thought the weak link would be the brakes, but so far I am runing out of talent long before running out of brakes, have not even felt a hint of fade yet.

To put the speed into context. On the main straight at monticelo if you hit the entry bend just right in the elise keeping speed up, get all you shifts just right keep your foot flat and brake as late as possible maybe it will get close to 125 mph.

In this Gt40 you can mess up the entry, revs are still limited for now to 5800 and I dont keep it flat through the kink in the middle yet, even with all that it still blows past 155 and thats with braking early.

Corners where in the lotus I had to keep momentun up, speed can now be added at will, the trick being not to add too much and balance the entry speed, power and grip.

Compared to a modern, you dont have the aero, and there are no nanies. Yet its
so reactive and full of feedback you can feel the limits and learn them.

I can see how on a modern, paddles, traction control, abs and some aero stability quickly make for easier and realy fast laptimes, against which you have running costs, weight and durability over mutiple laps. In the Gt40 any speed can only come from you, but with the light weight, grip, chassis balance and power it should be really really quick once one works up to it. This is what they used to call a feelsome car, somehtinhg you can sped years learing more and more, plus with a 50 yo design its not really going to be superseded by somehting new.

After looking and trying it was either one of these or a Gt3/Rs, cant say there is anything I regret about the decision, or build choice. But if you only had one car then a Gt40 would be very limiting/wearing on the street. Whereas Gt3rs or z06 can do it all.

I guess I am just an old school type of person, love the whole feedback and driving complexity, its a fully immersive experience.

 

some more build pics
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Motor started with a dart 302 block it was then bored 4.125 andthe crank is a Callie's lightweight nascar crank internally balanced with knife edged counterweights
Stroke comes out at 3.25 and with the big bore it's a short stroke 347.
The crank weights something like10lbs less than stock very light weight 5.4 con rods and custom Pistons means it not only has light reciprocating mass but rod ratios are really good.
Heads are the new afr 195s which were bought as raw castings and then machined
Solid roller cam and shaft rockers round it out. Induction is victor jr intake and a quick fuel carb.
I didn't go Fi because pretty much everybody I spoke to said a carb performs better stays in tune you can historic race with a carb and its lighter

The choice of a 302 block was partly historic but also weight a big thing coming from a lotus and it always pays dividends on track.
The motor as setup is a really snappy rever like Ferrari.

A lot of these cars have bored and stroked 351s to yed 427 cu about 550 feet s and maybe 600 horses all with hydraulic lifters, but you gain close on 100 lbs and it all where you leAst want it up high on top of the block.
The people who I spoke with who tracked these cars said you could def feel the extra weight on top of the 351 on track, you can't historic race with a 351 and the Tq kills the halfshafts unless you upgrade adding my more weight.
The bigger bore or fe motors also have heavy internals adding weight and are slower to revs due to reciprocating mass and journals.

As it is my motor puts out 480 ft s at 4900and 575 hp at 7100 there is still 565 hp at 7500 We built the transaxle after the motor was dunk tested and chose gearing to suit.
Given the broad power range it's not peaky or in a narrow range at all, but it's further up the rev range than a fe, hence the gearing to suit.

With the light internal mass and solid roller lifters it's a comfortable easy rever very European like a snappy Ferrari. The components used are really good for a 9k do motor so at 7k it should last well. Lubrication is dry sump with an external oil pump.

Even though it's been dyno run in I am keeping revs below 6k while I get used to it.

It's very slightly lumpy at idle and starts to pull strong from 2k. Between 4.5 to 6k frankly it already feels like too much, as in super bike fast. Makes my 600cc Yamaha feel like it's powered by a rubber band.

Couple more track days and I will explore further the higher revs where the last 150 hp lurks. Frankly anything more than it has would be UN driveable.

But yes if you were street driving a big bore 351 or a fe would mean you could run taller gearing and just shift at 3k or less, and any serious aceration is just a right foot away.

For me I put the emphasis on track ability broad power to avoid shifting when between some corners-
It's amazing how much hp you can get from American iron if you choose the components right. Well hp is easy, getting it smooth and durable costs similar $$$ to what building any hi po porche or Ferrari type motor will. Many a hot fodder misses this detail they make hp but it's trough stoke poor rod ratios etc so motors live short are rough and die catastrophically.
But the nascar guys they know how to build a v8 that can live at 8-9krpm for 500 miles or more.
An aluminum block would have saved another 30 lbs but then you can't historic race, the other option is a aluminum 351 bored and stroked to 427 which give the lower revs costs less to build, but then no historic sand you have a slugger not a rever.
Nice thing about building g a car up, it's like a tared suit, you close everything as you prefer.

Of course there is no badge or horsey on the front but as a driver that's actually preferable

 

I never really noticed the sitting on the right part, both seats are really close to the centerline. As most turns on a track are right sitting on the r is preferable weight distribution. The lhd gt40s have a cable shift which I thought not so great, the end is a rod shift in the sill, way better esp with the screen transaxle.


As you can tell many years of thought, even the build took 18 months.
So far the only issue has been a faulty clutch master cylinder easy enough to replace.

 

"The firsta rule of Italian driving is whatsa behind you doesent matter" as he rips the rear view mirror off and throws it out the Daytona convertible

 

Wheels were supplied by spf
Vintage wheels in calif supplied my second set, same supplier as spf same time daft wheels.
Wheels are aluminum not magnesium as in 60s the good is they are more durable the bad Imo quite heavy

 

Was at the track again today, even with my early stages of the learning curve this thing had no problem eating a new vette as snack. More like two different ranges of speed.
Course anew z06 might be a different story, but aregular stingray, might as well have been a miata.
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