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Old 02-27-2006, 11:41 AM
KNanthrup KNanthrup is offline
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ignition timing (in relation to rpms)

Ok so long story short, im a little skeptical about how accurate my timing marks are on my SBC 350. I was almost sure that everything was set right when I built the engine but it has some strange attributes (by the way it has a comp XE274 cam). When setting initial timing, it will not run very good under about 20* initial. It will run if I set it back from there, but not great, the idle rpms drop down a lot and it has a bad studder and very laggy/sudden throttle response... definitely does not feel right. So I can set it to around 20 or 22* initial and it runs great, the idle speed picks up a lot, good throttle response, etc. That brings the total timing to about 35* which is good also.

BUT if timing mark is not accurate and say what I think is 22* is really 16* then my total timing is really 29* not 35* which means I have a lot left in it. I have tried playing with the timing back and forth and I have not noticed any pinging when setting it up with more initial so I'm starting to get skeptical.

SO, my main unofficial half-whitted question is, how does the best initial timing typically affect idle speed? For example, is it usually at the point where the idle speed is at it's highest when playing with the timing only, or is it back a little bit from the highest idle speed, or is it a little farther back the fastest idle speed? I don't know if I'm making my question clear? Maybe it would even help to go on a scale of say 1 to 10 with 1 being barely running retarded a lot, 5 being the highest idle and 10 being tons of initial after the peak in idle speed.

p.s. I know I will need to use a more scientific and accurate method to check this but for now I'm pondering it as food for thought. Any insight is appreciated.
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