1. twin sidedraughts on a standard A12 is pretty much a waste of money.

2. twin SUs will perform fine on mildly modified engines. Webers on mildly modified engines won't do much if anything more than the SUs did, except use more fuel. The simple fact of having accellerator pumps means they have to use more fuel. it will sound faster but, which fools alot of people - just like loud exhausts often fool their owners into thinking their car is faster.

3. decent sized cams with SUs will give a very poor idle compared to webers. And once you get serious with camshafts, you will have to upgrade to webers - eg my old L20 would not even fire up with a 76 cam fitted with the twin SU's. I was told it wouldn't work, but I'm the kind of person who likes to see it first hand. I had the twin dellortoes ready to go on at the same time as the cam, but figured I'd fit the cam first with the SUs to see what happened.

4. My old old old 1200 coupe with twin SU A14 and lots of mods (ported head, about as big a cam as you can run with SUs, hi-comp mitsubishi pistons, ported oval head) ran 16.1 if memory serves. with reasonably sticky 205/60*13 yokohama A509 and 4.1diff - i think they were the A509. it was a long time ago...

5. so on an engine mild enough to run nicely on twin SUs, twin webers are unlikely to be worth the extra money. you'll get bugger all return for the money spent, except sound and looking tough when you pop the bonnet. but if you continue developing the engine you will get to a point with serious cams where you need the twin webers to support the other mods.

my L series 1200 evolved from
- standard L16 with twin 38mm Hitachis
- 72 cam, twin 38mm hitachis
- std L20 with the same 72cam and 38mm hitachis
- std L20 with 76cam and twin 40mm dellortos (108rwbhp)
- hybrid L16/18 with mildly ported SSS head, 76 cam, twin 40 dellortos (116rwbhp)
- hybrid L16/18 with mildly ported SSS head, 76 cam, twin 45 webbers
- wild SWR 1995cc L18 with everything you could think of (146rwbhp)

@L18_B110
Thanks for the info. I think I must spend the money on something else. Maybe do some work to the cylinder head?