I have collected various parts over the years with a view to getting a bit more out of my 63 wagon (single Zenith carb, single down pipe exhaust). It is a bog standard engine and I aren't planning on going nuts and setting it up for racing or anything. I just want a bit better performance.

Advice I have had to date is that the dual down pipe exhaust will have more impact than just fitting dual carbs. And dual carbs with a dual down-pipe won't achieve full potential without a better cam.

At the moment my collection of parts includes

- a pair of SU's in need of a rebuild and new needles
- an alloy inlet manifold for the SU carbs
- a cast iron twin SU / twin downpipe manifold
- a cast iron separate single outlet exhaust manifold
- a new twin downpipe from a 940 (it will fit if I cut the flange off and weld on 100mm shorter.
- a cam from a 1800 (don't know which type)

I am thinking that the least pain way to get a bit more performance and/or economy is to stay with the single zenith carb and track down a manifold for single carb and twin exhaust outlet (such things do exist - one ended on Ebay today). Next step up is to switch to the SU's with either the cast iron manifold or grind the inlet off and use the alloy inlet with the cast iron exhaust. Is this worthwhile without replacing the cam? Is it worthwhile having twin SU's with a single downpipe?

Any thoughts would be much appreciated.