Quote:
Originally Posted by Othen
I found the piece in the Green book about the B21FT model (I just missed it last night, I was both tired and dim), it was on pp 8 amongst the stall speed information:
... so it looks like the AW71 was mated with the B21, but only in turbocharged form as the B21FT. That makes sense as well because a turbo would have been a lot more powerful (162 HP I think) and so could have easily turned the higher gear.
I'm still far from sure about this, but it seems that Volvo didn't fit the AW71 to the B21a motor, and my suspicion is that it didn't produce enough torque - that is only my hypothesis, I hope I'm wrong. That doesn't mean it can't be done of course, just that it needs a bit more planning.
If that hypothesis turns out to be right, and I still want a 4 speeder I have a few options:
a. Get a used AW71 plus a prop shaft from Worcester and just nut and bolt it in with the current drive train. The good news is we know it must fit (somehow) because Volvo did it with the B21FT. I'm thinking I could just use the existing radiator set up and get two flexible hoses made up to go from one end of the AW71's cooling pipes - a short distance (maybe a foot or two) to the existing radiator pipes. The prop shaft and its centre bearing might need a bit of modification. It would make sense to change the engine's rear seal whilst it is apart (it isn't leaking, it just makes sense whilst I have the access). I quite like this idea because it is cheap - a few hundred perhaps. There is some risk in that it might end up as an over-geared 244 that can't pull top gear because the motor doesn't make enough torque.
b. Get a AW71 as above, but change it and the live axle at the same time (once I work out the ratio I have at the moment - then a lower one, probably 3.91:1) - so I'd sort of end up with a 740 drive train. This would probably take quite a bit more engineering mating parts that were not designed for the car or each other. It would be a better solution at the end though in that 1st, 2nd and 3rd gears would be lower than they are now, making for more spritely performance, but top would still be higher making for a better cruising car.
c. Swap the whole engine and drive train for a B23/AW71 from a 740 - much more ambitious, with decisions to make and dangers all over the place.
... lots of thinking for me to do over the winter - your thoughts would be much appreciated (also about the final drive measurement problem I had above).
Alan |
If you also check on the page you've got the screenshot from above Alan, you'll see the AW70 (near identical to the 71) was fitted to the B21F - no turbo!
Do you know the kerb weight of the RB? From memory i think they're about 1250kg fully loaded? The 740 is about 200-250kg heavier so the extra torque (not a lot but maybe enough to make a difference) from the 2.3 won't make much difference. In fact i'd expect the B21A 240 and B23 740 carb to give similar give similar performance with the same gearboxes.
As for more grunt, if you're going to the trouble of changing the engine, ideally you'd be looking for an early 740 2.3 carb and autobox to minimise the other alterations you'd need to do. Failing that it's either a twin-choke Weber (as already discussed) or as Luke suggests, a brace of 40DCOEs and then add a 4 branch manifold and possibly a cam change as well. I'm not sure if the V cam from the later B230/B200 engines would retrofit your B21 head but if not i expect Volvo do a similar profile for the B21 which would give more torque and power as well.
The other alternative would be aftermarket fuel injection, some kits use you existing carb as the throttle butterfly with a discrete Throttle Body Injector (TBI - Throttle Body Injection) and is commonly known as single point ijection, others use multi-point injection but still using either your carb as the throttle butterfly or Weber throttle bodies that mimiic the DCOE carb in appearance.
https://www.classicfuelinjection.co.uk/
Some more info there on aftermarket fuel injection. There is a Jetex exhaust system from the manifold back available but you'd probably still want a 4 branch manifold to make the most of it :
https://www.partsforvolvosonline.com...oducts_id=4753
More food for thought!
Quote:
Originally Posted by 360beast
B230, twin webers and 4 branch manifold  |
Mmmmmmmmm, me like!