Cobra 427 Build

[KugaWestie]

6 hours ago, Chris King - Webmaster and Joint North East AO said:

@Gary (KugaWestie) - North Oxfordshire AO There’s a Cobra leather interior for sale on locost site.

Can’t view it can you screen dump for me please?

[Kingster]

Quote:

FS, GD Cobra interior...
I’ve been re trimming my brothers Gardner Douglas Cobra and have the full leather pack thats been carefully removed. This might not be the right site to list it on but is anyone on the Cobra owners club/GD owners club or know anyone that needs an Interior.  

It’s a GD ex demo, Biege leather with maroon trim Heated seats with a new loom. Carpets been binned as it isn’t the nicest (maroon with beige trim).
 

Let me know if you need to make contact

[KugaWestie]

Price?

[Kingster]

That’s all there was on the post mate. 

I’ll send him a pm with your contact details if you want?

[KugaWestie]

11 hours ago, Chris King - Webmaster and Joint North East AO said:

That’s all there was on the post mate. 

I’ll send him a pm with your contact details if you want?

Yes please, give him my email address, I may be interested if I get some more info

[Kingster]

Done that mate 

[KugaWestie]

45 minutes ago, Chris King - Webmaster and Joint North East AO said:

Done that mate 

Cheers, we are in email contact 

[KugaWestie]

I have been thinking about gearing of the car.

At present I have a 3.5 Rover V8 from an SD1, and a manual gearbox which I think is an LT77.

Assuming thats the case, the gearbox ratios are:-
1st - 3.321
2nd - 2.087
3rd - 1.396
4th - 1
5th - 0.833

Included in my XJS donor parts when I collected the project was the Diff from the XJS. This is a 2.88 Powerlock from a 5.3 V12 HE.

I think this may be a bit long, great for cruising but not for acceleration.

I have been offered either a 3.07 Powerlock or a 3.54 Powerlock diff as a straight swap for my 2.88.

But I am struggling to decide which diff will be the best option. Obviously the 3.54 would be better for acceleration, but will it rev too high at say 75mph on a long journey?

What is the rover engine happy to cruise at RPM wise? According to Haynes Manual, the Original SD1 Diff would have been 3.08. This gave the SD1 a 0-60 time of around 8.5 seconds I think. That was on a twin SU Carb engine

I plan to fuel inject the engine and the exhaust will be more free flowing than a stock SD1 system. The combination of these will no doubt release some more ponies from the engine as well. Stock the SD1 was 155bhp. The engine has been rebored, but I dont know what to. Power output of maybe 180bhp with my spec?

I am guessing the Cobra will be a fair bit lighter then the SD1, which weighed in at 1367kg, but how much lighter I dont know, my guess would be around 1100kg when built? Say 250kg lighter?

Anyone able to give me any assistance here?

Discuss.........

 

[corsechris]

Wheel and tyre size will play into this as well of course, so factor that in as well. 

I didn’t keep records, but 3.07 rings a bell. I had a 4.2 with SD1 gearbox along with the Jaguar IRS in the Marcos, with, IIRC, 235/50/16 tyres and that seemed to work OK. It was a long time ago though, so I could easily be talking rubbish. 

Power wise, my own limited experiences, the first one in the cobra was a 3.5 on a Holley, stump puller cam, Vitesse pistons and that made about 200bhp ish. The 4.2 with a cam made 250/250 at Dave Walkers so I reckon that was pretty accurate. Think I still have the power plot for that somewhere.  They never seem to make all that much. Many are somewhat over hyped I suspect. They do sound nice though, and usually make good torque low down so tend to feel pretty good.

 

ETA, the Marcos started out with a 3.5 on carbs with a 3l Capri back axle so that was 3.09. Seems likely I went for the 3.07 jag to keep it close. I would have kept wheel sizes very similar too. 

[KugaWestie]

2 hours ago, corsechris said:

Wheel and tyre size will play into this as well of course, so factor that in as well. 

I didn’t keep records, but 3.07 rings a bell. I had a 4.2 with SD1 gearbox along with the Jaguar IRS in the Marcos, with, IIRC, 235/50/16 tyres and that seemed to work OK. It was a long time ago though, so I could easily be talking rubbish. 

Power wise, my own limited experiences, the first one in the cobra was a 3.5 on a Holley, stump puller cam, Vitesse pistons and that made about 200bhp ish. The 4.2 with a cam made 250/250 at Dave Walkers so I reckon that was pretty accurate. Think I still have the power plot for that somewhere.  They never seem to make all that much. Many are somewhat over hyped I suspect. They do sound nice though, and usually make good torque low down so tend to feel pretty good.

 

ETA, the Marcos started out with a 3.5 on carbs with a 3l Capri back axle so that was 3.09. Seems likely I went for the 3.07 jag to keep it close. I would have kept wheel sizes very similar too. 

Thanks.

I am aware that wheel/tyre size needs to be factored in.

At present I am leaning towards the 3.54 diff as that should give nice brisk acceleration

[corsechris]

What does the mph/1k revs in 5th come out at with that diff?  I get the desire for a nippy setup, but you do want a relaxed cruise too if you can. You don't want that V8 churning at 3k just to do 70. 

It's always a compromise isn't it. Still, not the end of the world to swap if it turns out not to your liking.

 

[KugaWestie]

I need to have a work out including an assumed tyre size

I want to get this right now as once that body goes on it would be an awful job to try and change it

[6carjon]

Hi Gary

When I first had my Seight with a factory 3.9, it was on a R380 box with a 3.36 diff.

It was fine for cruising around and plenty fast to begin with.....

As you know , unless you plan tuning your 3.5 its not a revving engine and happiest at 3-4K with a max of 5K unless you plan some modifications.

It majors on grunt not revs as you know so keep it in the sweet spot.

I would go for a 3.07 and keep it cruising and sounding wonderful.

Cheers Jon

[corsechris]

3 hours ago, 6carjon said:

Hi Gary

When I first had my Seight with a factory 3.9, it was on a R380 box with a 3.36 diff.

It was fine for cruising around and plenty fast to begin with.....

As you know , unless you plan tuning your 3.5 its not a revving engine and happiest at 3-4K with a max of 5K unless you plan some modifications.

It majors on grunt not revs as you know so keep it in the sweet spot.

I would go for a 3.07 and keep it cruising and sounding wonderful.

Cheers Jon

3.07 was what I was kind of hinting at too  

[H.7]

I have a Rover 4.3 V8 mated to an SD1 LT77 box with a Ford Sierra XR4x4 diff with a 3.62:1 ratio. 70mph = 3000rpm. Running 205/50 tyres on 15" rims. Huge torque so generally only using 4th and 5th gear on open roads.