New To This Forum With V8 Spitfire Mk4. Bmw E46 Diff?

[Spitfire8]

Hi, I've had my Spitfire for about 7 months. I didn't build it but bought it from the man who did. It has the Rover SD1 motor with Holley 390 carb and LT77 transmission. The rear axle is a rebuilt 3.27 in an otherwise standard rear end. It drives fine but I don't give it beans in 1st and 2nd and I drive sensibly. I have floored it in 3rd many times but don't corner on opposite lock! I've bought a 2.56 BMW E46 diff (these are available very cheaply) originally fitted to a 320D with 243lb/ft so it should be able to handle the V8, and will give me 70mph @ 2000rpm in 5th.  I've been searching for guidance on the conversion and it seems I need Rotoflex uprights with MGF/Metro hubs and driveshafts. I intend to use BMW inner joints and will probably have the driveshafts made up from 'half' of each. I don't think anyone has used the E46 diff before so I'll have start from scratch there. Let me know if it's been done as I'd love some guidance.

[Nick Jones]

Hi,

 

Welcome.  Sounds like an interesting car.  The diff is definitely the weak point, but clearly you know this!

 

I keep returning to the idea of using a BMW diff due to cost availability and excellent ratio selection.  However, not especially straight forward.  The E46 casing especially is a bit short of useful attachment points.  The versions from the E30, E36 compact and Z3 are more promising in that respect.

 

Using the roto-flex vertical links (or possibly MGF) opens up the options for suspension and driveshafts.  There's a fair amount of info on the forum about this already.

 

We'd to see like pics of the car if you have some 

 

Nick

[Spitfire8]

Thanks, Nick. I thought the E46 diff looked nice and compact but take your point about lack of attachment points. My car has been fitted with MGF rear discs but I think the VLs are original. I am wondering whether I really need the rear discs and whether it would be easier to go back to drums. There is a listing on Ebay http://www.ebay.co.uk/itm/351966039528?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT which has some useful bits if I'm going to do that, but maybe I should keep the discs? I just wonder how they've been fitted and whether the Rotoflex VLs and CVs would have required a different adaptation of the MGF parts. What would be a fair price for this stuff? Does anyone have a supply of Rotoflex VLs ready machined for the new wheel bearings? At this stage I am probably going to wait for the DfT to say how they are going to define Vehicles of Historic Interest as I would not want to lose Historic status by carrying out the conversion in a particular way if I would otherwise keep it. Under the 8 point system it is still OK with 11 points and might be OK with 9 after an axle swap, but I'd want to be sure and the 8 point system might be irrelevant anyway. I have put 1 picture on here if you can find it.

[Urge]

The price of them rotoflex parts is way to much.

 

they could all be scrap!!!

 

most of the rotoflex rears I have taken apart have had at lest one Vlink shot.

 

Unless I could see the parts in bits to examine them, (practically impossible, unless you live near by) I would personally only pay £60 max for that lot.

 

a lot of you may say more, but I am willing to bet, even at £60, you wont be getting much for yr money.

 

its very much like buying a car that needs a full rebuild, what do you actually get for your money!!!!  most of what you bought get scrapped 

[Nick Jones]

Doubt the Spitfire benefits much from rear discs - but if they are there and working well (including front/rear balance!) - why not.  You would need a different caliper brackets as the roto links are different dimensions where the back plates attach.

 

GT6/Vitesse drums are bigger than Spitty drums anyway.  Consider discs from my Vitesse from time to time but the Vitesse is heavier and longer wheelbase.

 

That looks like a pretty complete roto rear set.  I know "Tavistock Steve" - he's ok.  Look like quite strong money, but then they are not very common now - would be ok if they come apart ok and have no damage.  However, you never know how much aggro you are going to have getting rusty looking stuff like that apart.  The long trunnion bolt through the wishbone can be (and and often is) a complete bitch.  I used to do machined links on exchange, but stopped a while back for various reasons.  If you can come up with a bare set then Paul (Mr Speedy on here) can machine them for you.

 

The points system...... yeah.  Who knows.  And how do you define "rear axle"?  I have stock diff and links but CV shafts - how does that measure?  If I add a foreign diff nut keep the outer ends stock - how does that measure?  This on a car that came with roto from the factory.....

 

If they start buggering about with this and want to apply it retrospectively then lots of folks are going to be in bother!

 

Can find the pic?  Did you upload to the gallery?

 

Craig detailed pic tutorial is here

http://sideways-technologies.co.uk/forums/index.php/topic/5917-adding-pictures-to-posts/

 

Nick

[Triumph-V8]

Welcome and an interesting project!

I started similar on the TR6 but discontinued.

Maybe a good idea now to go on!

 

My idea was to use the diff for cv joints what allows to

have the driveshaft a bit longer than used in the coversion

kits because the adaptors from TR flanges to CV joints are

no longer needed.

 

What I have is the rear housing, I employed a 40mm aluminium

plate that i converted to a backplate with a plain rear on the milling machine.

There I fitted the original holder for the rubber joints from the TR4a.

So rear is ready to fit into TR6

 

Front has a 5mm steel plate already fixed at the diff to accept some

custom holders for the original front rubber mounts.

 

As the original front TR6 steel plates get rare I did not want to kill one

to get the required parts and also did not want to spend the time to

produce a similar item by welding and doing parts on the lathe.

[Spitfire8]

Welcome and an interesting project!

I started similar on the TR6 but discontinued.

Maybe a good idea now to go on!

 

My idea was to use the diff for cv joints what allows to

have the driveshaft a bit longer than used in the coversion

kits because the adaptors from TR flanges to CV joints are

no longer needed.

 

What I have is the rear housing, I employed a 40mm aluminium

plate that i converted to a backplate with a plain rear on the milling machine.

There I fitted the original holder for the rubber joints from the TR4a.

So rear is ready to fit into TR6

 

Front has a 5mm steel plate already fixed at the diff to accept some

custom holders for the original front rubber mounts.

 

As the original front TR6 steel plates get rare I did not want to kill one

to get the required parts and also did not want to spend the time to

produce a similar item by welding and doing parts on the lathe.

Did you use an E46 diff? I'm thinking maybe a new backplate may be the way to go but with extra folded over and going forward to take the leaf spring. I'd do it in steel and take it to the front mounts too. There is a square 'knob' of casting on the top of the diff that could be drilled and tapped for one large fixing bolt/stud.If the steel carrier is strong enough for the suspension loads (no sideways loads now) then it only needs to hold the diff as securely as it would be on the BMW. I've found a local engineering firm near Lincoln UK that can sort out laser cutting and folding for me. The build chassis for crop sprayers amongst other things but are also car enthusiasts.

[Spitfire8]

The first picture is as it is and the second is how I want it. I'm likely to do the body mods before I do the final drive. The previous owner, who built the car, did some good work and spent £13000. The reshaping of the bonnet does mean there's plenty of room for a big vertical radiator but I don't like the fussy detailing and hole in the bonnet.

[oldtuckunder]

Ah that Spitfire V8, I think I saw it for sale a while back and thought it interesting. I think I agree with you about the body mods it could do with being a trifle more understated.

 

They do some decent air plenum's for the holley idelbrock carbs that reduce the height significantly and allow you to run air ducts to front mounted filters down in the nose, filters are cheaper and you can save a few inches in height.

 

Good luck with the project.

 

Alan 

[Triumph-V8]

Yes, mine seems to be a E46,

cheap and widely availiable.

 

The rear backplate from steel might be difficult.

The crownwheel looks out of the housing and

the backplate must provide some space to accept it.

 

So 40mm thickness is more or less required

and that might become a bit heavy if made from steel?

 

So maybe a intermediate backplate from aluminium and a steel

plate bolted and folded to it might be a solution.

[motov8id]

e36 diff

[Nick Jones]

Odd bonnet.......  Why was that done?  I know it is possible to get a V8 in a Spitfire without any bonnet mods at all as I've seen one.  I don't think it's very easy though, which is why most have a modest scoop.  Also a few running a GT6 bonnet instead.

 

You might find this thread interesting

 http://sideways-technologies.co.uk/forums/index.php/topic/5192-8pot-spit/page-6

Unfortunately the first three pages date from before the forum move so there are no pics.

 

Nick

[Spitfire8]

Thanks Nick,

I think the builder thought of it as a hotrod, hence the portholes and customisation. The dash is customised too. It just looks wrong as it is but I think it looks quite good with my revisions, dare I say better than original. I've been thinking about the back end and there will, of course, still be side-loadings through the transverse leaf spring as well as the new lower links so the diff carrier plate will need to be really strong.

 

Triumph-V8, I think a lot less than 40mm will do the backplate in steel and I can get a hole lasercut and boxed over for the protruding crownwheel. It'll need a filler plug too.

[Urge]

slightly off topic, But a diff and shaft question from me plz.

 

What is the length of half shaft that are used to marry a Subaru diff to a Roto Vlink. Using the Subaru Lobo/Inner C/V 

 

only roughly plz.

 

Want to check the travel on my milling machine as I might be able to make a few sets of these for my self and any one else that needs them.

[zetecspit]

I don't have the actual measurement, but it is a std rover 100 shaft from the Nicks setup, There should be a measurement for that somewhere.

In reality, 20mm longer would probably be ideal, as used on the KDT setup.That would set the inner joint a but further in. I did have that measurement somewhere, but I think is disappeared when my 'puter died

[Nick Jones]

As I happened to have reason to measure one at the weekend..... I can tell you that the total length of the shaft from the tip of the outer UJ thread to the flat of the UJ/CV adaptor is 513mm compressed and 530mm extended. The actual shaft bar itself without CVs will be maybe 80mm less.

 

Nick

[Urge]

Thanks for the reply, 

 

I had not intended on going to my workshop today, hence my question

 

However, I did have a need to go and so I dug out a GT6 roto shaft with doughnut fitted, just the shaft mind, 

 

I am happy to say, the Milling machine table lengh is quite capable of coping with a shaft of that length, 

 

As I have two sets I will need, one for my spitfire and one for the GT6, I will probably end up making my own.

 

As I dont want to hack this topic, Ill say thanks for your help guys, and leave it at that