Timing on 91 3.9
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Registered User
Joined: Nov 2017
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From: Rogersville, Mo.
Timing on 91 3.9
Can anyone explain the setting on 91 3.9? The manual it only states set on #1 on TDC, rotor pointing to #1. Is that at #1 cyl. or #1 on the cap? I get all the the shaft and slot pointing at the bolt hole of intake. The rotor slot on Dist. pointing 3 -o-clock ( facing engine ) Then we get into the 10 degrees before TDC. Can someone simply this? Appently, you can set alignment dots 180???
Champion
Joined: Jan 2013
Posts: 4,737
Likes: 374
From: Northwest Louisiana
Yes, you can set the crank 180* out on the cam; remember, the cam turns at 1/2 the speed of the crank.
Before dropping the dizzy in, use the thumb-on-spark-plug-hole method to verify it's coming up on the compression stroke, not the exhaust stroke.
Or take the valve cover off, and verify that both valves are relaxed when it's at TDC.
I don't have a 1991 factory service manual, but in my 1988, it clearly states to line the rotor up with the #1 spark plug connector on page 8D-19.
As to the 10* BTDC; that's set with the motor running and the engine coolant temperature sensor disconnected to force no advance.
You set that like any other old dizzy; loosen the clamp, use a timing light on the #1 spark plug, and adjust against the timing marks.
RwP
Before dropping the dizzy in, use the thumb-on-spark-plug-hole method to verify it's coming up on the compression stroke, not the exhaust stroke.
Or take the valve cover off, and verify that both valves are relaxed when it's at TDC.
I don't have a 1991 factory service manual, but in my 1988, it clearly states to line the rotor up with the #1 spark plug connector on page 8D-19.
As to the 10* BTDC; that's set with the motor running and the engine coolant temperature sensor disconnected to force no advance.
You set that like any other old dizzy; loosen the clamp, use a timing light on the #1 spark plug, and adjust against the timing marks.
RwP