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Story by Tim Suddard and Carl Heideman • Photo courtesy Savannah Race Engineering
Does running the correct distributor matter? For decades we have seen the ads and heard…
Accuracy is one important component. A hot reliable spark is the other, especially considering the higher combustion pressures in a modified race engine. Hard to make power at 6,000+ rpm if one cylinder misses three of the 50 sparks per cylinder generated in a four-cycle engine running at 6,000 rpm. It gets worse as the rpm climbs.
I know it's a little late, but it would have been nice to see how the 123 Ignition distributor stacked up against the other ones. I'd be anxious to know if that hefty investment is worth it.
Your engine is running 45 side drafts with 10.5:1 compression ratio. The stock home market European Lotus twin cams were 10.25:1 and ran 40 DCOE or Del Ortos. Are you choking the 45s down? Is this because of the different cams?
4 cyls with 90* between each cap terminal and a grand total of 20* of ignition swing (did it have vacuum advance too?) are good candidates for making a (tight) distributor work even at high rpm. Less than 1* accuracy has to be considered pretty damn good! I think actually just being aware of the spark timing variation that's possible at high rpm is the first step to not getting bit by it. A lot of ohc engines running timing belts have the harmonics of the belt and then one or two more gear interfaces adding up slack to the distributor's drive system. If you get into 8+ cylinders engines and boosted engines running high rpm, the reasons for getting away from a distributor grow substantially. Even though the dyno test itself didn't exactly illustrate the pros/cons of accurate ignition timing, just bringing up the issue and talking about it is something worthwhile. 
Jeff at Advanced Distributor built me a period correct Lucas race distributor over 10 years ago that has never let me down and looks great.
In reply to dougie :
No engine bay has a right to be that clean and pretty. Ok. Maybe I’m a little jealous. :)
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