tr7 or sprint gearbox and back axle into 1850?

[Oli_88]

Sprint axle and box will survive that quite happily.
1850 stuff. No chance, 110 and it all goes bang quite often.
Tr7, I don't know. Jonners probably will... I'm not entirely sure they're the same as the 1850 stuff, but I don't know.

[scotchydoodle]

cheers oli, as you may have guessed by aberdeensprinters posts I've now got his rotten sprint minus engine & box. I was going to find a sprint o/d box and hopefully cable tie it to an old alfa twincam engine. Stock engines are around 130-150hp and can be tuned for road use easily up to 200hp but I was going to keep thing sensible for everyday use. I won't be doing any trackdays or racing but just wanted a good fast road motor for the annual high speed pilgrimage to Le Mans. The best times in the past were in my old TR6 and alfa 75 twinspark, and I want the best of both worlds now. I know the sprint motor is a good un but you just can't beat old alfa engines for noise and power.

[Jon Tilson]

Yes its been said several times that the "small" triumph stuff is only up for about 110 bhp. A stock GT6 or TR7 is about its limit.
The single rail box has supposedly uprated bearings for the TR7 application....yeah right. Most small boxes should have been rebuilt with the stronger bearings by now as thats all the usual suspects have been selling for a while. Its just an extra roller in the bearing. The needle rollers and the diff still wont cope with much more. I don't drive that hard...no fast starts etc and am generally sympathetic mechanically but ERO has eaten 3 old diffs and its current one, which had about 50k miles behind a 1500 in its early life, has just begun to sing a bit too much for my likeing after another 25k or so...It was also too much for a second hand o.d of dubious provenance, spinning the cone clutch. Current 3 rail box and od is okay but it ate the first one even though I had rebuilt it...lunching 3rd gear! So I know what I'm talking about...

Next time its getting a Sprint diff. Your Alfa idea is interesting but how does the twin spark go from transverse to north south? And its quite tall.
Given the faff sticking in XE's and red tops, only one of which I know runs half well...why not just stick with the known good Sprint engine? A reliable 150 bhp is not a problem...

Jonners

[scotchydoodle]

The alfa engine is essentially the same as a regular unit with onventional flywheel/clutch etc except that where the heavy flywheel normally is, there's a lightweight plate with ring gear bolted to the back of the crank a bit like the front of the 1300fwd engine. Some engines have the hole in the end of the crank for the spigot bearing, some don't so crank may req drilling on end. other than that it's a case of just fitting a flywheel from an older conventional twincam alfa gtv/spider etc, then all the malarky associated with mating odd engines & boxes.
I have aberdeensprinter's old sprint now and plan on using it as a mule to get it all together over the coming year or 2 (decade). This won't be a megabucks project so if it all looks a bit impossible, it could be changed along the way.
I know sprint engines are good for the power but I just love the way those old twinsparks are bulletproof even when tuned to 180hp+ (alfaholics do engines up to 220hp in road spec) and they sound magnificent. My last alfa 75 cost me £800, I took it to Le Mans a couple of times and it would spend the weekend doing donuts, drifts etc an would still give 35mpg at 100mph on the way home. I defy anyone to give one a good spanking and not fall in love with it.
They don't look like a modern engine and nobody seems to have done one yet, which is a bit of a tease if you ask me.
any ideas are always welcome.
sometimes the obvious way to do things is just too easy.

[scotchydoodle]

Just re-read your post jon, "Your Alfa idea is interesting but how does the twin spark go from transverse to north south?"
The engine I'm planing to use is the 8 valve twinspark from the rwd alfa 75. It's the last evolution of the classic alfa twincam from the fifties and not the iron block 16valve fiat derived engine from the nineties (the bent valve special). These cars had a rear mounted transaxle with flywheel and clutch mounted under the back seat!
Let the fun begin.

[Jon Tilson]

Should be fun....I'll look forward to hearing about progress...

Jonners

[cliftyhanger]

Keep the 1850 subframe. Only real difference is the engine mounts. (I think. but I used the old toledo subframe with the TR7engine/sprint box, but fabricated engine mounts, jag type, oe £14 each)
Clutch, only difference is the plate. You want sprint/gt6/vitesse/2000 etc plate. Spline count is the difference.