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I've got a mildly modified 351C, with a 4160 with the original jets and accelerator pump, and a lighter vaccum secondary spring. How do I figure out which jets are best?

Would more accelerator pump would be worthwhile? From what I've read - it sounds like it would be worthwhile to switch from the as delivered 25cc pump to the 50cc accelerator pump, and switch back if it bogs off idle. Or try different pump cams. (I've only read about this ... otherwise I got NO clue)

Right now the performance is good off idle, but not spectacular, it accelerates solidly through about 3500 rpm, at which point it gets outta control. The plug color is between gray and light brown.

I have followed the basic procedures, and I'm not sure what is next. Thanks for any advice on this!
 

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The only way to get a good read on jets is trial and error..I would try moving the pump to the richest slot and work from there..also check your timing..Cleves like advance..but not too much as they are really high winders..thats why your engine really wakes up after 3,500..it is real happy in the higher ranges

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Thanks! From both yawl's posts, I'd guess it would be worth playing with the initial timing again. I'm already pretty close to 16 degrees BTDC at idle. I know I might be chasing shadows trying to tune in a whole lot more under 3500 rpm, but I figure it'll be worth the effort if for no other reason to learn more about my carb/engine setup.

That reminds me of an article I read ... it was saying to reduce the total amount of centrifugical advance to run more advance at idle and low rpm, without pushing the high rpm advance too far ... I just remembered that. I wonder if that trick is worthwhile for a cleveland?
 
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