How much damage to my 1/4 mile ET?

dbv8 · Post by **dbv8** » Mon Feb 25, 2013 9:05 am

So the TVR runs the 1/4 mile in 12.4 @ 111 NA with 275 @ wheels.
With the standard 3.45 diff i am at about 5000 rpm in 4th as i run the traps.

I pulled the leaky diff out this weekend and John Reid is rebuilding it for me with 3.08:1 gears. So motorway cruising will be more civilised with the possibility of a whopping 30 mpg.
I also want to do a vmax event and the extra gearing will come in handy.

But what effect will this have on the 1/4 mile. Looking at the gearing i reckon i can now do the 1/4 in 3rd gear getting close to 6000 rpm which is a smidge over my peak power.

We will see at York come Easter i guess.

kiwicar · Post by **kiwicar** » Mon Feb 25, 2013 10:42 am

If you give the clutch enough stick off the line then if anything you should be 1/2 to 3/4 second quicker by virtue of cutting out 1 gear change, but really it is down to you, can you bring yourself to launch at 5000 revs and and slip the clutch until you have matched the road speed to the revs? Ahh I love the smell of burning clutch in the mornings . . . it smells of. . . Saxo!

Best regards
Mike
Ps you could always fir t 3 plate 4.5" tilton then you can give it as much stick as you want, just don't try ar drive it in London!!

dbv8 · Post by **dbv8** » Mon Feb 25, 2013 11:08 am

Talking of clutches

This is mine after less than 1000 miles.

Pressure plate looks bad but feels ok to the touch

Flywheel badly scored

The damaged flywheel weighs 11kg. I will get it skimmed. Will a rebalance be necessary?

I have another flywheel whick weighs 12.4kg but the face is undamaged.

What do you reckon? Use that? Get it lightened?

kiwicar · Post by **kiwicar** » Mon Feb 25, 2013 12:06 pm

Hi
I am not the person to ask if it is a good idea to lighten a flywheel I have seen one let go . . . in all cases I would say no, skim it to get a flat face, ballance it if the skimming takes material off a counter weight OK, but lighten it, only if you are not that attached to your lower legs.
If you want a lighter flywheel then get a lightweight Steel or Ally one they are much cheeper than sorting out what you are left with when a lightened 30 year old piece of work hardened Steel/ iron lets go.
As regards the clutch, look into a 4.5", 5.5" or 7.25" tilton multiplate on a flexplate or even a full on drag clutch with centrifugal counter weights and an apropriate gearbox.
Best regards
Mike

dbv8 · Post by **dbv8** » Mon Feb 25, 2013 1:46 pm

These are boths TVR flywheels.
About 24 and 27 lb respectively. I am sure i heard the '500's were about 20lb. Ive never heard of a TVR flywheel let go...

ian.stewart · Post by **ian.stewart** » Mon Feb 25, 2013 1:59 pm

I would go for a steel flywheel every time, after killing a flywheel up the pod a few years ago, something about the clutch wear dosent look right, the wear looks uneven across the pads, should the flywheel have been machined for a raised platform for the friction surface???
I ran a Helix conventional clutch on my cortina with 300hp and no problems at all,

stevieturbo · Post by **stevieturbo** » Mon Feb 25, 2013 2:17 pm

Of more concern, why has the clutch got into that state in such a short period of time ?

Have you been slipping the crap out of it ?

1/4 is hard to judge. It will depend what traction you have, and how far each gear drops you after a change. Sounds like it could be a fairly substantial rpm drop which might put you in a crappy place, which will cost you time.

Launch wise, the taller gearing might actually help with grip. So ET may be the same, but trap speeds lower.

dbv8 · Post by **dbv8** » Mon Feb 25, 2013 3:35 pm

stevieturbo wrote:Of more concern, why has the clutch got into that state in such a short period of time ?

Have you been slipping the crap out of it ?

I confess.
I fitted this clutch towards the end of the season last year and met a few mates at Shakey for RWYB. I still havent got round to fitting the linelock so i was reversing into the bleaches and dumping the clutch then left foot braking for the burnouts. This worked ok until i 'forgot' and used my old technique of heal and toe. I guess the MT streets and rear brakes on were too much and i spun the clutch for a good few seconds before i realised. Still ran 11.4 on the gas tho but i guess the damage was done.

dbv8 · Post by **dbv8** » Mon Feb 25, 2013 4:15 pm

ian.stewart wrote:I would go for a steel flywheel every time, after killing a flywheel up the pod a few years ago, something about the clutch wear dosent look right, the wear looks uneven across the pads, should the flywheel have been machined for a raised platform for the friction surface???
I ran a Helix conventional clutch on my cortina with 300hp and no problems at all,

Probably a combination of not having the flywheel refaced when i fitted it and maybe not enough beddig in period. I maybe did 300 miles normal driving on it. I have over 300 bhp NA but i also race using nitrous that takes me to upward of 500 lb/ft and an organic plate just cant cope so thats why i had to fit the paddle kit.

dbv8 · Post by **dbv8** » Thu Feb 28, 2013 1:29 pm

Just picked up the flywheel from Banda Engineering.

A little extra taken off the back

The front nice and smooth

Is it highly recommended i get a balance check?
A couple of sources have said its not necessary

mgbv8 · Post by **mgbv8** » Thu Feb 28, 2013 8:31 pm

dbv8 wrote:Talking of clutches
This is mine after less than 1000 miles.

Pressure plate looks bad but feels ok to the touch

Flywheel badly scored

The damaged flywheel weighs 11kg. I will get it skimmed. Will a rebalance be necessary?

I have another flywheel whick weighs 12.4kg but the face is undamaged.

What do you reckon? Use that? Get it lightened?

Why is only half the pad worn?

mgbv8 · Post by **mgbv8** » Thu Feb 28, 2013 8:32 pm

My diff is 3.07:1 in the MGB Del.

stevieturbo · Post by **stevieturbo** » Thu Feb 28, 2013 8:34 pm

Ideally yes...but then ideally you'd have it balanced with the rest of the rotating assembly too...

But more than likely it will be completely fine.

stevieturbo · Post by **stevieturbo** » Thu Feb 28, 2013 8:36 pm

mgbv8 wrote:My diff is 3.07:1 in the MGB Del.

But you're automatic...isnt quite the same.

What sort of rpm do you see from launch through to finish ?

mgbv8 · Post by **mgbv8** » Thu Feb 28, 2013 9:09 pm

stevieturbo wrote:
mgbv8 wrote:My diff is 3.07:1 in the MGB Del.
But you're automatic...isnt quite the same.

What sort of rpm do you see from launch through to finish ?

It used to be manual Stevie. This is the stock MGB V8 diff ratio with 4 speed + O/D gearbox.
They had to inhibit O/D in 3rd gear on the stock box because it had too much torque and would damage 3rd gear.

With the same diff on the auto I launch at 2000rpm in stage and then shift at 4500 rpm in 1st and 2nd. Then just let it run to about 5200 rpm across the line for my low 10 second runs with a 2800 rpm stall converter and 28" tall tyres.