Valve overlap and idle

PostPost by: peg_pilot » Thu Sep 04, 2008 12:55 am

Since I last posted about the poor idle quality in my Elan, I noticed in the Wilkins book following page 160 there is a reprinted report saying that the "Super S/E" engine (which I presume is the sprint ?) using Stromberg carbs has a rough idle due to increased valve overlap.

My (Stromberg) Elan has reground cams with 0.405" lift and 50 degrees of overlap at .020" lift. The Bean catalog seems to indicate the sprint cams have 32 degrees overlap at .020" lift, so I am running quite a bit more overlap than the sprint.

Is the increased overlap on my cams the likely cause of my rough idle ?

I notice also that the lift and duration of my cams is very close to the Bean 114 cam. Can anyone using these cams comment on the idle quality ? Do Webers idle better with large overlap than Strombergs ?

Thanks for any help.
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PostPost by: memini55 » Thu Sep 04, 2008 2:13 am

We have a +2 and an S2 with 114 Bean cams and both with webers, both seem to idle pretty well. A little on the lumpy side but not too rough.

Mark
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