08-07-2011, 09:24 AM | #1 |
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Erratic timing
Ref: 8BA stock - with Pertonix ignition and coil. NGK B 4L plugs
stock ignition wires. Warmed up to 160 - 170 degrees. Checked the timing at 550 RPM, vacuum line plugged, vacuum gauge connected at base of carb. At idle the timing consistently jumps a few degrees advance beyond the setting of TDC. Watching the vac gauge, it is at 18 in. vac., however the needle moves from 17 to 18 continuously. (plug gaps set tight ?) Compression checked at it is 1 - 140 5 - 145 2 - 140 6 - 135 3 - 140 7- 140 4 - 150 8 - 145 What causes the timing to fluctuate as it does? thanks
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08-07-2011, 09:33 AM | #2 |
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Re: Erratic timing
I never saw a stock engine with this much compression?? A variation in timing could be caused by a bad distributor. But valves come to mind??
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08-07-2011, 09:47 AM | #3 |
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Re: Erratic timing
Ron - the heads were cleaned up about .010" after a bad head gasket.
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08-07-2011, 10:08 AM | #4 |
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Re: Erratic timing
one degree is not much it could be set on 17.5 that means it is varing .1
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08-07-2011, 10:09 AM | #5 |
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Re: Erratic timing
we are talking about a light that is digidal and rounds off at 1. degrees
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08-07-2011, 10:10 AM | #6 |
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Re: Erratic timing
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08-07-2011, 10:36 AM | #7 |
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Re: Erratic timing
I described the timing fluctuation in my book and explained how to measure and to correct it. The basic problem is usually excessive camshaft thrust clearance. The nervous gauge needle is probably showing a slight intake valve leak.
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08-07-2011, 02:10 PM | #8 |
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Re: Erratic timing
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08-07-2011, 05:14 PM | #9 | |
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Re: Erratic timing
Quote:
Plug the vacuum and tighten the spring tension up a bit by turning the eccentric pins and retest.... |
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