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Old 05-13-2024, 11:56 AM
Popeye Popeye is offline
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Join Date: Nov 2013
Location: Eastern MA
Posts: 32
Hi all,

Just getting back to the engine tune. (I was distracted by noise/vibration from under the car. I think it was the exhaust rattling against the rear motor (transmission) mount cross plate - and hopefully fixed.)

Two questions as I roll up my sleeves on the ignition:

1. My distributor vacuum advance has two ports: I assume one for retard, one for advance. The port furthest from the distributor will not hold a vacuum and does not move the adjustment rod. The port closest to the distributor holds a vacuum, and rotates the internals clockwise (I assume advance).

If I am right - I have advance but not retard - how critical is the retard function? Searching the forum suggests it is only needed for emissions at idle - and not needed for general operation. (If anyone has Bosch 1237122611 to sell, let me know!)

2. The timing guidelines seem to be vastly different between the Haynes manual and my Mercedes Service manual. With no vacuum connected, at (1) idle, (2) 1500 rpm, and (3) 3000 RPM, the Mercedes manual calls out: 1-9, 31-39, and 41-49 degrees. The Haynes manual calls out 0, 19-28, and 29-35 degrees. The diference is stark... what am I overlooking? (I have not yet checked to see where the motor currently is timed; like I said it is fundamentally running well, and I assume I need to "tweak" vs. "adjust" things.)

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