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Non Rotoflex CV conversion?


Roger
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Hi All! 1966 Vitesse 2 Litre Mk I: I’m planning to replace my original Vitesse engine with a 2,5 and I would also like to upgrade the rear axle to cope with the extra torque by converting to CV. There is plenty of information about converting Rotoflex to CV on the forums, but my Mk I Vitesse does not have Rotoflex. Can I still upgrade my non-rotoflex car (?) and if so, what parts do I need? @Nick Jones and others here on the forum seems to have a lot of knowledge about this. Some advice from the experts would be much appreciated. Thanks in advance.
Roger.

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Chick Doig used to sell the Mk2 rear wishbone chassis brackets you would need. Not sure if he still does, but maybe worth a call.

Back in the late 1960's people used to fit the stronger van spring and then a spacer to get negative camber. Bit on the hard side!

The diff can be the weak point, It's not the BHP, it's the torque of the 2.5. I had one recon diff lock-up after 20K and it took out a Rotoflex coupler. The couplers appeared to take the extra torque before the diff locked up. But they were the original type, I am not to sure of the quality of the present ones. Mike Papworth is the person for up-graded diffs.

Dave

 

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I did the very same thing to my MK 1 Vitesse 2.5 after snapping a driveshaft on the 2012 Round Britain Run.

I sourced the parts over time before fitting,i was lucky at the time that Nick was still doing his excellent conversion with MGF bearings,i went for the full setup built up by him as i trust him more than myself.

You need the wishbones,tie bars,uprights,and the wishbone bracket to weld to the chassis,.these are available from Canleys(still available i think).And obviously your choice of CV shafts.

I also went for a new 3.27 diff with a modified carrier.Also a Saloon gearbox with J type overdrive.

It has produced a quick car but also one that will cruise at 80 no problem(on private roads.

Also make sure the brakes are in good order,i found the standard setup with a set of Mintex 1144 pads work great.

I am doing the same thing to my Herald 1500 at the moment.Using the Rimmer/Jigsaw CV shaft.Got a decent price on one of their many sales.

Steve

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30 minutes ago, dave.vitesse said:

Chick Doig used to sell the Mk2 rear wishbone chassis brackets you would need. Not sure if he still does, but maybe worth a call.

Back in the late 1960's people used to fit the stronger van spring and then a spacer to get negative camber. Bit on the hard side!

The diff can be the weak point, It's not the BHP, it's the torque of the 2.5. I had one recon diff lock-up after 20K and it took out a Rotoflex coupler. The couplers appeared to take the extra torque before the diff locked up. But they were the original type, I am not to sure of the quality of the present ones. Mike Papworth is the person for up-graded diffs. 

Dave

 

Thanks for your quick reply Dave! I realize that the original diff will be a weak point, but at least I have eliminated one possible cause for a break down if I can upgrade the shafts. I will definitely search for a better diff also. Unfortunately they are heavy and expensive to ship to my remote location.

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43 minutes ago, Steve P said:

I also went for a new 3.27 diff with a modified carrier.Also a Saloon gearbox with J type overdrive.

Thanks for your advice @Steve P A 3.27 diff would be perfect (no OD) but I thought they are very rare and hard to find? Which type of car donated your 3.27 diff? I’m not planning to do any drag racing or hill climbing so I hope the original gearbox will cope until I find a replacement.

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I had a 2.5 vitesse, but used a saloon gearbox which although massively strong had a low first gear.

I destroyed several 3.27 diffs, but never a diveshaft. 

I fitted a 3.63 diff tat coped very well with the torque, survived many years, then did service in my zetec spit (155BHP, used for grass roots motorsport so not an easy life)

So unless you can get the Rotoflex conversion parts, I think you are stuck with the std driveshafts. But they do cope perfectly well (mostly)

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Roger, my thoughts on this........

The CV joint driveshaft conversions (any of them) don't necessarily increase the torque handling ability of the rear end whether you start with rotoflex or swing axles.

They are intended to do away with the troublesome (mainly the non-Metalastik copies) Rotoflex doughnuts and also the marginally sized UJ.  One version also converts to stronger hubs and modern bearing packs.

Apart from the diff which is the same throughout, the main weaknesses for the swing axles are the universal joints and the occasional (but serious!) fatigue fractures near the hub/bearing, which usually causes the loss of a wheel and brake drum - three wheels on my wagon...... and no brakes 😓

You can of course fit a CV conversion to a swing axle car - but first you have to convert it to rotoflex.  Not a bad thing to do as it is certainly less likely to bite you if you do something daft like lift off mid-corner!  Conversion not entirely straight forward though.  You need:
- Preferably the complete rotoflex set from a Vitesse or Bond 2L donor including chassis brackets for the radius arms.  GT6 has different radius arms and chassis brackets. 
- The handbrake guides from a rotoflex vitesse (or Bond 2L) preferably with the section of floor they attach to.
- Chassis brackets for the main chassis rails (Canley Classics sell these though they can be made) 

Things to watch for
- Brake pipe routing is different.  Is possible to use the swing axle routing though the hoses will rub on the CV gaiters given half a chance.
- Some rear outriggers have the extra holes inboard for the roto radius arm brackets.  If not, making them will be a huge pain as they need crush tubes.
- You can just about use the swing axle handbrake mechanism if CV shafts are fitted but the geometry is wrong and adjustment varies with load/ride height.
- In most cases you can use the original dampers with the original brackets.  Sometimes there is quite a bit of offset forward or back though.

Whatever you do you'll probably break something if you go drag racing......... most likely the diff......

Nick

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Hi @Nick Jones, Thanks for sharing your extensive knowledge about this, much appreciated.

I was mainly concerned about safety and the loss of a wheel at high speed. There are plenty of reports of that happening on the forums, and apparently excessive torque is not needed to make it happen.

If brand new “high quality” drive shafts where available (?) for a Mk I Vitesse, then I would definitely buy a pair. If I lived in the UK then I would probably source the parts needed for a rotoflex/CV conversion, but shipping and custom tariffs etc makes it difficult to achieve here on the island. From your description it also require a lot more parts and modifications than I expected, so I will try to upgrade the Mk I version as much as possible and drive carefully!

The only reason for building a 2,5 liter instead of a 2-litre engine is simply the fact that a 2,5 liter engine was the only engine I could find within reasonable driving distance (I drove 750 miles to collect it). Otherwise I would prefer a 2-litre Mk II engine.

Thanks a lot again for all your input, this forum is great!

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Roger, 

You are quite right on wheel loss due shaft breakage being the biggest risk. This is more a fatigue / wear leading to fatigue issue than torque as you say.

I meant to comment on new replacements. As has been discussed at some length here and on Sideways Technologies, at least some of the new, non OE shafts available are at best “doubtful” and at worst “dangerous”. Issue being that the UJ trunnion forging is not properly attached to the shaft itself.

Best advice seems to be to stick with low mileage OE..... Maybe keep an eye out for a rotoflex set, or consider something based on the MGF vertical links as others have done.

You can enjoy the extra urge of a 2.5 without driving like a hooligan....... probably!

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Yep, Summers Bros in the USA make them. Not cheap........ must be well over a grand landed these days. Mainly bought by the racers.

Were thought unbreakable until Mr Vowel (where has Andy gone?) managed to snap one mid race. Not sure if anyone else has. They are almost certainly the strongest around.

 

 

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