In Search of 501 Mid-range carburation perfection!

Maestro, SEI-V
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simonnorthroad
Posts: 388
Joined: 16 May 2017 10:57
Location: Bath, UK

In Search of 501 Mid-range carburation perfection!

Post by simonnorthroad »

Was tinkering ONCE AGAIN with my 501 engined, L5-cammed 350 last night in search of mid-range perfection. Very puzzling really and just goes to show what a dark art carburation is

On the dyno last year, it was shown to be spot on at full throttle (Id done plug chops) but at midrange to be "off the scale rich" to quote Mr Dyno man and the graph - Id thought it weak as on a slightly closing (and only ever rolling-off, never accelerating) throttle at 4000rpm, it spits back thru the carbs - a usual sign of weakness! but when I dropped the X18 needles even one notch to lean it off, it made it much much worse. So now the needles are lowest notch/as high as they'll go.

Last night I tried X6 needles nearly identical but with a slightly longer taper (so ever-so-slightly weaker), and as before it made it run worse, like dropping the X18 needles - hesitant and stuttery at 1/4-1/2 throttle.

After blasting up the road at near constant mid-throttle, the plugs were 'pale-biscuit' so not evidently rich.

In short dyno suggests it's rich, practical experiment suggests its lean. Very strange.

Still its taken me to the S of France then through the Pyrenees to Andorra and home via Santander so I cant really complain, and there's not much of a flat-spot, it's just not as seamless as my std 500!
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