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Help with inconsistent timing '78 280z


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Hey everyone, newbie here with a question that can hopefully be answered and maybe it's a common problem (I can hope right)

 

Anyway, I am picking up a 78 280 from a friend. All stock, it will be getting a v8 of some sort or a turbo swap in the near future. First I need to smog the stock engine....From what I am told the guy can set the timing and fire it up and it will run flawlessly. After driving for a bit, turn it off, then the timing will be off...

Is this a comon problem that anyone can give me most likely fix for? Or should I wait to see the car in my hands and diagnose it from there? Thanks for the help everyone and I cant wait to get this thing going on here :)

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The problem you describe is not likely, if even possible. The distributor is driven off the crank via a geared spindle. Unless the distributor hold downs are loose I can't see how this would occur. Maybe something broken in the vacuum advance plate or something. It all seems very unlikely to me...

 

One issue I've seen on a 280Z distributor is the pickup gap to the trigger wheel can be off. You need BRASS feeler gauges to set this gap as I recall, and I don't know what the gap is supposed to be, you can download a factory service manual off of http://www.carfiche.com, or maybe someone here will pipe up and tell you what the spec is.

 

Were it my car to buy in CA I'd try to find a 75, unless it's a track only thing.

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There are two slotted adjustments at the base of the distributor. If neither of those are slipping, then the gear on the quill shaft may be slipping (it's only pressed on). The only other item that comes to mind at the moment is the mechanical advance mechanism in the distributor. They can get gummy with age and it may cause inconsistent timing.

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OK, I had this happen after having my L6 rebuilt many years ago. The key that keeps the gear on the crankshaft that drives the distributor and oil pump had been improperly installed and worked its way out, allowing that gear to turn slightly on the crank.

Mike

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