The V8 Owners Forum -

I think you will find its harder to achieve these high speeds than you think, especially if aerodynamics are against you.

Best I managed with a RV8 was around 160 over a standing 1.25miles.

My car never did like going much above 6000rpm though...whether there was a problem, or a simple lack of power...dont know.

At that point, I was doing a little over 120mph over the 1/4, 1600kgs weight.

Well that is the problem on the GT40

It has a Renault 21 gearbox and big tyres but still turns about 2900 at 80mph. so 170 is a little over 6000rpm

To get a longer box would require going to something like Porsche or ZF and throw about £5000 at it for the box alone. (Then clutch bell etc on top.)

But some in line boxes may have better ratios so the 6000 rpm may equate to a higher terminal speed.

In the GT40 world they recon on anything up to 20% loss of power through the transaxle (From engine dyno to rolling road) to stop meltdown transaxle coolers are fitted and is another area you need to look to ensure your power generated is going to the floor and not into warm parts. Likewise getting a clutch to take the torque will be another challenge.

Still I like the idea and would love to be a camera car at your attempt! (anyone volunteer to be camera man?)

Keep us posted.

Cheers
Ian

If the engine produces peak power at 6500 and didn't drop off too fast, and to get the necessary power it will have to have good heads so it should do, then you only need about 30 miles an hour per thousand revs, not realy very high gearing. For the power you want you are going to need a pretty stout box, if you used a T56 it should take the torque and they have 6 speeds, two overdriven should give you plenty to play with.
best of luck
Mike

You would need to optimise your gearing for it... a 6 speed might help...or it may dot, depending on rear diff ratio.

Im using a 3.55 diff, 0.74 5th gear, 0.5 6th, with 26" tyre ( diam )

For top speed, 6th is totally useless for me.

Standing mile recently seen 190.7mph, 6600rpm in 5th gear.

Car was performing very badly above 6300rpm due to valve sealing issues.


Not rover...but 200 will come

I think my current gearing is very good for it if I can ensure car pulls hard til 7000rpm.

I was thinking of lower final drive ratio and the .62 top version of the box and working around that, what I think he will need is a closer ratio version of the t5/6 which I suspect you could build out of gears 1 to 4 of the ford version of the box Ian has (I think the one in the monaro is the same) and gears 5 and 6 out of the GM cars with the .62 sixth gear. my reasoning is that a rover based engine making this power is not going to have a very wide power band and will probably bog down on upward gear changers on a 5 speed.
Mike

kiwicar wrote:I was thinking of lower final drive ratio and the .62 top version of the box and working around that, what I think he will need is a closer ratio version of the t5/6 which I suspect you could build out of gears 1 to 4 of the ford version of the box Ian has (I think the one in the monaro is the same) and gears 5 and 6 out of the GM cars with the .62 sixth gear. my reasoning is that a rover based engine making this power is not going to have a very wide power band and will probably bog down on upward gear changers on a 5 speed.
Mike

Ratios are random. Viper's, Camaro's and Corvettes have the tall 5th and 6th. I think the Mustangs use the shorter 5th and 6th, same as a Monaro, and I think the Aston Martins also use the shorter 5th and 6th....albeit with the closer ratio 1-4

The closer ratio box, actually has the tall gears...the box with the wider 1-4, as the shorter 5th and 6th.

Well at the mo I have rover lt77 box, and jaguar xjs running gear front and back, I don't know if the box would be good for 200, enginewise I would like to stick to rover but looking at spending a lot to get there like wildcat/turbo money

on the wheelbase issue the fensport toyota wasn't much longer than moggy and did 200 .



James

The Fensport car would have around 700bhp, and far far better aerodynamics.

I think it took them about 1.5 miles to achieve 200+ though.

Not sure if they have attempted it with their Celica ? It should be much better than the Corolla