I've been pursuing this (just got back from Sydney with a ca20 spec 71b) -= but not quickly enugh as the layshaft in the coupe is cactus, getting noisier as the days go by (hence intermediate step of a 60 series dogleg which was for sale here a little while back).

Here's my take on things. THe ca20 bluebird 71b is the last of that style (iirc) the rest are 71c. Certainly the C is a better one, but I think that the 71b will tolerate practically anything an a15 could put it through. I'll throw on top of that, that being from a ca20 bluebird, they are (relatively) a little newer than L series bluebird 71b boxes.

I'd also add that they (teh ca boxes) are a slightly wider ratio set (if the info I've found on them is accurate the L series wide ratio 71b ratios VS CA20 ones)

s1/;2 s3/ca20
1st..3.321 3.592
2nd..2.077 2.057
3rd..1.308 1.361
4th..1.000 1.000
5th..0.833 0.813

So they'd be less suitable for a highly modded smaller NA a-series, where closer ratios would pay off, but for an a-15, esp a streeter, or alternatively one that is turbo or supercharged, then the wider ratios would probably make it a better all round car.

http://www.locost7.info/gearcalc.php

is a very nice program that lets you compare different gear and diff ratios (and tyre sizes) and engine redline/upshift rpms, and in graph and table form show how much rpm drop you'll get with each upshift, and the (theoretical) speed the car will be at if it hits X rpm in gear Y etc.

Better still, you can run the program a few times, so in one window is one gearbox, in another separate window is another one, and you can compare really quickly.

As much as there _is_ a lot of work to convert a 71 box (of whichever type), I think it is the one with the most merit at the present time. The toyota gearboxes are getting harder to find, and more expensive. The 71b boxes are still around, just have to find em (I missed one at pick a part - found it, and couldn't get back there before the darn thing had been crushed) And they are strong.

Certainly trans tunnel mods are no trivial matter, but if that's what it takes, that's what it takes I guess. For the record I haven't done it (yet) but have done that sort of stuff on other non datto cars. With a bit of work and an oxy torch, you could (if you are careful) cut the existing trans tunnel, not all the way out, but along the top and a few other places, then heat and 'massage' into a new wider arch, and that could then have the 'gap' filled with a new piece of sheet metal. That would then 'hide' the new sheet metal up and over the trans, rather than visible cuts all the way around the whole tunnel, and a whole new tunnel section welded in. Done that way it might not even be noticed by anyone looking at it and not knowing it was there in the first place.

There's (realistically) no getting around the need to remove the input shaft and machine down the spigot 'finger' on the input shaft to suit a series spigot bush sizes.

I suppose, a _small_ amount of dough could be saved if a few people got together and got them all done at once. because the process is the same on each one. Won't save millions, but might offer a small price break.

Thanks Jmac hence the persistence with the 71 series.
In the long run its the most available and cheapest.
Input shaft machining is trivial like you said just need
someone that can be bothered doing it and sure will if
there is more than one to make it worthwhile to operator.

The tunnel massaging and adding sheetmetal undernearth &
then sealing it up or tar coating it will hide it well.
Its like body work and how nice you want the finish.

I found the ca20 is 3.321 in some manuals could be wrong.

What do you think Jmac of using the cut, shut, fit inside
the other bell, tapped, thread and adhesive it all round?

Any adhesive that can be recommended for alloy? has to be
permanent bonding and better than liquid nails :)

Just saves alot of welding, heat and can be repositioned
spun around to tilt engine a tad and allow better manifolding
space much like Simon has done to his 71/56 setup.

The smaller bell suits smaller race clutches and clears the
tunner entrance better than the larger L or CA front bell.

D, what about using the CA16 5-speed? They have a smaller bolt pattern than the CA20.

Jmac, why do you not like the 71C, they are pretty much the same as 71B on the outide, aren't they?

DD, Though clutches vary, BellHs size all same ca16/18/20 :(
I think Jmacs saying B series is enough but C is better.

I should probably clarify - I don't have anything against the 71c as far as its merit goes. By all accounts they are stronger/more reliable yet again over and above the 71b.

Where I'm coming from is (at least as far as my luck has gone) is that the 71b boxes seem a little easier to source, or at least are more affordably priced. That being the case (and even with a price break, it's still an expensive conversion in all seriousness) I basically come at it from the point of view that it'd be hard to destroy a 71b behind an a15 in a 1200 - basically a motor with less torque than a ca20 (or similar torque, I suppose, depending on state of modification) in a considerably lighter car. So in effect the 71b will 'do the job' so I guess I don't need to look further.

In Aus, at any rate, the series 3 bluebird with the ca20 motors seem to have been thrashed a bit less on average (I suspect it's purely because more people had second hand s1 and s2 bluey's as their first car, and thrashed them relentlessly. I would imagine that in a couple more years, the ca20 71b boxes will end up the same way, so we are probably toward the end of the 'window' to find cheap ca 71b boxes in good enough condition to either use as is, or to be in good enough condition that new bearings/synchros etc will make them effectively as good as new.

It would seem (and i know I'm being _very_ vague on a lot of this, and it's a reflection of the quantity of info out there and the fact it isn't always in agreeance) that the 71b (and for that matter c) boxes were subject to various small tweaks and re-visions over their lifespan, so relatively the 'last' of each model is likely the one to have. Based on that, a ca sourced 71b would likely be one of the better of the 71b boxes (specific ratios and their suitability notwithstanding).

I've made a quick mention (on the phone) to a couple of people about an idea I have that will involve _some_ tig welding of the bellhousing, to make them fit an a series, but instead of a whole new bell, or one adapted from an a series box of some type, this one simply uses 'sleeves' or something that looks like 'crush tubes' - but made of alloy - and aligning the box to an a-series, then drilling/grinding and welding in these tubes, one for each bolt hole, and of course the locating/alignment dowels. It should drastically cut down on the amount of machining and welding, An additional piece could be made from a small block of alloy, to relocate the starter motor to the a-series position, then some rough (but functional) pieces of alloy to cover/blend it into the bellhousing.

Good idea but won't the ends sitting against the block just be floating in mI'd air? Unless tiged against something solid this would create a weak spot in the design. Unless you need the clamping force of the bolt to the block to stab slide it, placing extra pressure on the welds holding to tubes.

Probably the most cost effective method

I actually think cut & shutting a smooth 56a/60 series
A series bell w/ 71 series bell, then drilling, tapping and gluing is easiest/cheapest as there is no welding or heat.

Also another bonus is that it saves space as the big bell of
the 71 creates tunnel entrance issues that for example Simon
has avoided somewhat with his cut and shut 56/71 hybrid.

Either Devon
http://www.devcon.com/products/produc ... um%20Liquid%20%28F%2D2%29

or will resort to heat using durafix

The larger bells fit the 1200 tunnel automatic version. Easier to cut the spot welds and fit the auto version tunnel compared to cut & shut the bellhousing -- isn't it?

Sorry if I wasnt clear, I meant fitting smaller front section of the bellH from 56/60a into a midcut section of the 71 series box, tap/threading then adhesive. eg.

Attach file:

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  boxes ca a and auto.jpg (49.06 KB)

Got it. Just need an alignment jig to hold the faces of both part parallel to each other. Well, that and center the two parts, which might be trickier.

Still, wouldn't fitting the auto tunnel be easier? It's all stock that way. Additionally if the transmission needs replacment later, you won't have to mod the replacement to fit the tunnell.