Rear axle Strengths

[ian.stewart]

Just a bit curious about Sprint axle strength, Im guessing the half shafts are vulnerable, as I have seen some shafts that may be GrpA and they are on a different level, Obviously a LSD would go a long way to making the shafts survive, other options?

[Carledo]

Just a bit curious about Sprint axle strength, Im guessing the half shafts are vulnerable, as I have seen some shafts that may be GrpA and they are on a different level, Obviously a LSD would go a long way to making the shafts survive, other options?

The generally accepted number for a Sprint axle is 250bhp a bit more with an LSD fitted. Oddly the diff case/pinion bearings seem to be the first point of failure rather than the half shafts Though the shafts do have a bit of whip in them that is hard on oil seals in higher powered cars. I gather there's a mod to put an intermediate bearing in the shafts, but I know no more than that it exists, i've not needed to know more as i'm still working under 200bhp currently.

I reckon that's enough for a Toledo/Dolomite since you can't put much more than that on the road in a satisfactory manner. The Carledo, with only around 140BHP on tap was a hoot to drive, thanks in part to considerable weight reduction (to go faster add lightness, I had the kerb weight down to 760kg) but would still light up all the way through 1st and halfway through 2nd gear. My PB on the 1/4 mile in that car was 16.014 @91.03mph. I'm expecting an ET in the 13s for the turbo'd mkII model with 200-220 available.

IMO that makes it good enough, unless you are trying to build a sub 10 second car.

Steve

[ian.stewart]

I dont want a silly quick car any more, 11s was fast enough, But looking back at my exploits, I used Toyota celica axle from a series 2 celica, the baby mustang one the half shafts are bigger dia than a ford 9", and a good plated LSD,
looking as sprint shafts, its quite feasible for me to machine some shafts, not that I want to, Med tensile steel is a nice material to use tho, It might be easier to ship a shaft to Moser and get a pair made,
In a good lightweight car, example a stripped out all steel anglia, running 4.1:1 open diff and a 158hp pre crossflow, was running a 13.2s

[Carledo]

The Carledo has a completely stripped interior, no bumpers or spare wheel etc and GRP front end and wings. I think the 3.45 axle didn't help my 1/4 mile time, I was only just hitting 4th as I crossed the line. But on the other hand it was also my daily driver and that highway diff ratio gave me an average 36mpg, thrashed everywhere! Which was very useful!

Be interested to know how you got 158bhp from a PCF (presumably 1500) I thought i'd done well to get 120 from a 1650 overbore of a 1500 PCF with all the usual add ons! Mind you, that WAS in the mid 70s and in a MKI 'Tina estate. So it was still on points etc. Even that made it a quick car in it's day, but I never put it on a strip to find out HOW quick.

Steve

[ian.stewart]

158hp from a pre x flow, surprised many people, on round mains too, it was a 1600 block, think 1760, it was detuned from over 165hp to give much more torque and drivability,
A fella I know had a green Mk1 cortina with what was basically a scratch built pre x flow, the last incarnation I remember was 2 litre plus, and about 200 hp, I saw one of his old blocks, it barely resembled a ford block inside, I think the cam bearings had been offset so he could get crank throw, what was left of the cam journals had been ground away, I seem to remember the bores being moved too and a one piece wet liner made ( looked like 2 figure 8s end to end) and furnace brazed into the block.

[SprintV8]

Ken Clarke mentioned that he was having some Competition Spec half shafts made.
Tempted myself,.

When I visited his workshop a short while ago.