Hello guys... thought i'd add my two-penny-worth (sorry, two-cents-worth!)...
Which carb is best for power? The one that has more than enough airflow for the job in hand and is clibrated to give the absolute best fuel mixture under all conditions.
The myth that Weber/Dellortos give more power than SUs is generall y caused by the ability (or lack, there of) to tune the Su properly. Not that many folk know how because they do not understand the instrument. Plus, the plethora of needles available makes it a somewhat expensive instrument to cater for, unlike Webers that every Tom Dick and Cobber can cope with because so many otehr vehicles use them and have done for eons. Dellortos fall somewhere in between. BUT fot the individual it is WAY cheaper to sort an Su than a Weber/Dellorto because all you have to pay for is one needle, maybe a piston spring. ?20 tops. One of the others... check out the cost of chokes, vents, emulsion tubes, jets etc. Multiply by two and sit down and take a good long swig of Wild Turkey.
My little sojourn with Graham Russell last year proved that SUs propeerly applied will out BHP, and over a wider rpm range than a Weber.
And that leads me to the next point - Attempting to fairly assess a singel SU against a single side-draught Weber/Dellorto (henceforth W/D coz I'm tired of doing teh full name check each time) is fundametally flawed. To make a more comparable comparison you should be talking twin SUs against a W/D. Noe we're getting close. Check out who has the best 'straight shot' at the port now.
Back to the single for the moment. You really have to get with how to make an SU work properly to make a serious comparison between a single SU and a W/D. Something that Graham and I have had plenty to discuss about following my visit last year. The dyno testing illustrated a number of issues not peviously understood by either of us. As his LS now confirms, you need a bigger SU than most think of using to make the performance these 1360/1380 engines are capable of.
Which moves me on to... Kevin - your recent rolling road test was hardly fair/comparable. Graham's engine is very old indeed and subject to mega-miles of trashing. Your motor is fresh and has one of Graham's newly developed camshfats and cylinder head on. I'd be a little un-happy if such a motor was mine with the benefit of several years R&D and got beaten by a well worn out and thrashed 8-year-old engine. It has damn near nothing to do with the carburation.
Oh - 'ram-air effect' - go see Calver's Corner on this subject on my website
www.calverst.com
Where were we - oh, right. W/D on swan neck manifolds taht need no bulk head mods. These will only work well when ceratin explicit criteria are met. Almost all on the market don't. Graham and I have discussed making one that would work OK. But we get back to teh same question... Why? When a big single SU on one of his manifolds or twins on one of mine work so damned well...
And for the record - go for an HS6 rather than an HIF. The later may be a more finely tunable instrament as far as fuelling for economy and performance goes, the former is so much easier to deal with and will give better all over power. The HIF has a temp-sensing bimetallic strip controlling jet height. It leans the mixture out when under bonnet temps get up a bit... Just what you don't need on a performace engine. And teh HS fuel bowl carries more gas in it...
The downdraught carb, by the way, generally gives more torque/performance because of teh manifold design. It has inherantly more plenum volume than a typical W?D sidedraught.
And SUs most certainly do have an accelerator pump jet... piston depression on initial throttle opening causes an enrichment of the fuel.
Anbody still awake?
KC
if it isn't a stromberg or holley or fits on a holdford they don't even want to know, statement like you made are put forward by our american friends and have been continued here because we follow them instead of the europeans who by the way have lead the world in inivation for car design since cars began.glad to see you have crossed to the dark side and run a sidedraught 
