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As you know I have been experimenting with my Holley's automatic choke since spring. To give it more air during 50 degree summer mornings I removed a good portion of its butterfly (some call it a flap) and that did the trick as it would instantly start then fast idle. But as the morning temperatures are now in the low 30's I found my choke was way too lean.

So I decided to put an unaltered butterfly in it then experiment with its adjustment. At the "zero" setting it chugged out black smoke like a coal fired steam engine. Way too rich. I adjusted it 3 marks lean and it was still way too rich. I adjusted it 3 more marks leaner and it was still too rich. I now have it adjusted about 1-1/4" from its "zero" mark and it seems to be about right as it no longer chugs.

Engines with long duration camshafts are very temperamental to start when using an automatic choke on cold mornings because they don't pull in as much air as stock engines. What works well at 30 degrees may not work as well at 40 degrees and may not work at all at 50 degree. So their correct choke settings can vary a lot depending on how cold it is.

Just one of the many prices to pay when we alter our engines.
 
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