Cossflow versus BDA

[KayTee]

Okay, I'll stick my neck out.

 

I am, as several people will know, currently restoring what used to be a Lotus heap of rusted frame tubes and tatty alu, including butchered history.

 

A rebuilt chassis later, I am reasonably close tho finally dropping the engine into the car.

It used to sport a rather tired pre-711M x-flow engine.

 

Then I managed to snap-up a professionally built BDD/R, dry-sumped 711M block, steel crank (72mm), 5" steel conrods, 1 size up valves, L1 & BD3 cams, semi-electronic ignition and 45 Webers. (effectively being a short-stroke 1600 engine)

 

That was it ! It *had* to go into the car !!

 

It will be anything but modern and tame, sporting a 3.89 Quaife LSD/ATB life axle, a straight-cut Quaife pro 4-speed box and twin-plate sintered clutch.

 

It will definitely not be as tame and every day useable as std. K of VX cars, and may not last as long as even tuned versions of those engines. On the other hand, it will be *exactly* what I dreamt of smile.gif

 

The engine has allegedly been dynoed in a Ralft F3, on slippery tyres, and delivered 142 bhp @ the wheels. I know, this doesn't mean squat.

Roger and other experts, what do you guesstimate ?

What other items should I look out for, hardware-wise ? (Rev-limiter!!)

 

It will be a 2nd car, obviously, so won't do all that much mileage for the difference in life-expectancy to Ks or VXs to matter all that much, but I still want it to be good for touring.

 

What do you all tink of this, am I on an 'OK' path, or totally down the wrong road ??

 

Thanks for any and all pointers !

 

Regards - Karsten

[Roger King]

If it's as good as it sounds - brilliant.

 

The power at the wheels figures sounds very realistic (possibly a bit pessimistic), but without seeing the engine in bits it's difficult to be sure.

 

If it's properly set up on a rolling road and the operator understood the needs of roadgoing (as opposed to pure race) engines, you may be surprised how driveable it is. You may need to set up again though because the exhaust system in your car will probably be very different to one on the Ralt.

[KayTee]

Thanks for your quick reply, Roger smile.gif

 

The Ralt had a 4-1-open-air 2.5"-final 'exhaust'.

It will definitely need re-jetting of the carbs in my application. I managed to source a 4-1 header kit for a BDR Caterham, and this'll go into a 2" side-exit can.

 

Driveable ? Darn, how about L1&F1 cams then? wink.gif Just kidding ! How about twin L1s, however ? I understand that these will require modification to the head and/or pistons ? But then, it'll be mad enough as it is, while still leaving plenty of room for a "madder than Knievel" future biggrin.gif

 

Thanks & best regards - Karsten

 

Edited by - KayTee on 15 Nov 2001 10:55:45

[oilyhands]

Hi Karsten,

 

Having run a BD with F1s, L1s and L1/BD3 I reckon you have a good combination, two L1s tends to give a bit of a torque hole which is maddening, F1s are just bonkers.

 

There's some bumph below on profiles for the BD (although many are LTC profiles) I recently sent this to Vinnie..

 

L2s are quite warm at 302 degrees, the next steps would be (in ascending level of scaryness) L1s (306/10mm), DA10s(312/10mm), BD4s(316/10mm) , DY1s(317/11mm), DA12s (322/11mm) ,F1/EA1 (324/10/11mm) and DA1s (326,10mm), there are some PH4 and PH5 cams as well at 314 and 324 degreees/11mm. All of these are going to lose you some low down grunt, L2s are a pretty good compromise, and I've seen L1/DA10 inlet/L2 exhaust used in combination too, they work pretty well, the lobe centres are fairly close together at 102 degrees (its worth checking your cam timing since the TC is quite sensitive).

---

 

If it were me I'd stick with the L1/BD3, these make the engine quite tractable and should be good for close to 190-200 but you'll need to turn 8000RPM or so to get it.

 

Oily

 

Edited by - oilyhands on 15 Nov 2001 11:20:53

[Simos]

Hi Elie,

smile.gif in truth I've never weighed it but I seem to recall (going back here) that the original documentation with the '90 car said 620kg..? I think Caterham quote a lot less now with alloy blocks and gearboxes etc. I suspect the generic K is now 550kg-ish

 

I'm pretty sure I have L1 inlet and L2 exhaust cams (going back not quite as far) which gives good traffic driveability but goes completely mental beyond 4,500. As my (serious Scooby) friend said "Holy **** !". I don't have pics myself but you can see the engine on Roger's website here

 

Hope to see your 480kg BD some time, can compare to my 680kg (me in it) beastie, are you planning trackdays next year ? Cadwell ?

 

Cheers, Simon.

 

Edited by - simos on 15 Nov 2001 17:59:38

[Roger King]

Simon,

 

Your memory for camshafts is correct!