Timing Question
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From: Bowling Green KY
Car: 87 IROC-Z
Engine: 350ci
Transmission: T-5
Timing Question
I have my timing set at 22 degrees advance at idle and 36 degrees advance at 3000rpm. Does this sound like too much at idle? The car runs very well and idles well and starts easily. I don't hear any dentenation even with 87 octane gas but 22 degrees seems kind of high. What do you guys think?
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From: USA
Are you disconnecting the vacuum advance to check the initial timing?
If you aren't, that sounds about right. If so, something's wrong.
12* initial is very common on a SBC. If you have the stock vacuum canister on there, then 10* is the norm. The mechanical is usually 10-14* Add all those together and you're right on the money.
If you aren't, that sounds about right. If so, something's wrong.
12* initial is very common on a SBC. If you have the stock vacuum canister on there, then 10* is the norm. The mechanical is usually 10-14* Add all those together and you're right on the money.
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Joined: Jun 2002
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From: Bowling Green KY
Car: 87 IROC-Z
Engine: 350ci
Transmission: T-5
Thank you for the reply. I realized I don't even remember if thats with the advance disconnected. If it is I'll post again so maybe someone can help me figure it out.
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From: Loveland, OH, US
Car: 4
Engine: 6
Transmission: 5
36° total timing with no vacuum advance is about right. 22° at idle seems way high. About 10-12° at idle would be more normal, with about 24° of centrifugal advance starting at 1200 RPM and all in by 2500 RPM, plus another 10° or so of vacuum advance, would be a normal performance advance curve.
Vacuum advance should be hooked to ported vacuum, i.e. the vacuum at its connection should only exist when the throttles are opened off idle. Sounds to me like you have it connected to the wrong place.
Vacuum advance should be hooked to ported vacuum, i.e. the vacuum at its connection should only exist when the throttles are opened off idle. Sounds to me like you have it connected to the wrong place.
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From: USA
Originally posted by RB83L69
36° total timing with no vacuum advance is about right. 22° at idle seems way high. About 10-12° at idle would be more normal, with about 24° of centrifugal advance starting at 1200 RPM and all in by 2500 RPM, plus another 10° or so of vacuum advance, would be a normal performance advance curve.
36° total timing with no vacuum advance is about right. 22° at idle seems way high. About 10-12° at idle would be more normal, with about 24° of centrifugal advance starting at 1200 RPM and all in by 2500 RPM, plus another 10° or so of vacuum advance, would be a normal performance advance curve.
Vacuum advance should be hooked to ported vacuum, i.e. the vacuum at its connection should only exist when the throttles are opened off idle. Sounds to me like you have it connected to the wrong place.
The proper port will give you vacuum during idle and a part throttle 'cruising' speeds. The only time you should NOT have any vacuum off that port is during WOT or under acceleration. Is that what you meant by "opened off idle"?
If you're going to check your curve or total timing, you should check it with the vacuum port connected, as well as not connected. Since you can't hold it at WOT, you're going to get some vacuum advance at part throttle.
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