denicholls2 wrote:Where I disagree is about the "not straightforward" part of exchanging Strombergs and SUs. There may be minor linkage differences, but numerous cars of the era bolted on one or the other over time. I think you'll find the same to be true if you investigate the two designs.
I've not done the conversion myself, so if you have I'll defer to your better knowledge, but when I researched it as an alternative to rebuilding the Strombergs on my car, three potential issues were identified:
1) Clearance; the dashpots on SU's are taller than those on the Strombergs and can apparently foul the bonnet bulge on Elans.
2) Needle profiles; if you read the chapter on the Stromberg engine in Miles Wilkins, you'll see that the mixture took a bit of getting right, even for Lotus, and the SU conversion is no different. Even with the work that Lotus did, the Stromberg engines have a reputation for a slightly uneven 'hunting' idle, and it takes a bit of experimentation to get to a needle profile that works equally well on the SUs.
3) Ignition profile; again, if you read Miles Wilkins, you'll see that the ignition advance on the Stromberg engine is a bit of a compromise, and the SU responds differently and has different needs again. Unless you get mappable ignition, chances are your ignition advance profile will end up a bit of a compromise based on a bit of a compromise!
Nothing that can't be sorted, but I don't think it's as simple as bolting a pair of SU's on, fitting XYZ needle profile, and off you go...
Having said all which, I'd echo Mark's comments: my Stromberg S4 was perfectly tractable, torquey and quick, and I certainly wouldn't rule out a car simply because it was on Strombergs.
In particular, the 'not as free revving as Weber' comment you frequently see is a red herring; because the Stromberg is a variable choke design with a damped piston, the throttle response certainly isn't as crisp as Webers/Dellortos if you are simply sitting on your driveway blipping the throttle (being damped, the choke lags slightly behind the throttle opening), but in actual driving it doesn't make any difference, basically because the car can't out-accelerate the carburettor response.
But given two equally good cars, for equal price, most people would take the Weber/Dellorto option over the Strombergs.