Volvo RWD 120-130 Forum

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Idle surge while setting timing. 120-130 1969

posted by  pearl on  Tue Mar 28 14:02 CST 2006
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last visit: Sun Jun 7 09:41 CST 2009
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Can ANYONE tell me why the idle on a newly rebuilt B20 would KEEP SURGING as I’m trying to set the timing? It's got one of those SP cams in it and rebuilt SUs on it. I’ve been attempting to set it anywhere between 10 and 16 BTDC (heard different things from different folks). I’ll get it in the neighborhood, and then it takes off, again.
Tuned carbs and checked for vacuum leaks, many, many, times.
Jeeze, I know the B20 is a good engine, but I’ve been wishing for the ol’ B18, or maybe a Ford Escort. Oops!







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Idle surge while setting timing. 120-130 1969

uid 4846's pic
posted by  JohnMc on  Wed Mar 29 01:36 CST 2006
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last visit: Thu Oct 23 07:42 CST 2014
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Do youhave the vacuum retard hooked up? If so, disconnect it, and (IMO) leave it disconnected. At idle the vacuum in the manifold sucks the timing down into a retarded state, which drops the idle speed. Using this method to slow the motor down (instead of manifold vacuum) results in a less stable idle.

If that doesn't work, check for leaks downstream of the throttle. I'd say 'vacuum leaks' but I'd get nit-picked! :D
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I'm JohnMc, and I approved this message.







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