It has been my experience that the shaft of the stock distributor is made
of rubber and gives the symptoms you are all describing. It is nothing at
all to find as much as 2 degrees difference between the neighboring lobes
of the cam due to the bent or rubber shaft as I call it.
----- Original Message -----
From: "Larry Young" <cartravel@pobox.com>
To: "Randall Young" <Ryoung@navcomtech.com>
Cc: <fot@autox.team.net>
Sent: Wednesday, September 08, 2004 11:46 AM
Subject: Spark Scatter
>I guess I'm confused (not unusual) about the definition of spark
> scatter. Is it defined as errors in ignition timing
> 1. causing random fluctuations in the timing at a given cylinder, or
> 2. such that the cylinders are not firing at equal intervals (when
> fluctuations are averaged out)?
> Maybe it is a generic term which encompases both of the above. I first
> heard this term when talking to a tech person at Pertronix, and I
> understood it to mean definition 2. However, I think you guys are
> talking about definition 1. I'm not sure what problems could cause
> random fluctuations, but couldn't it be more than just wobble in the
> distributor shaft, e.g. timing chain issues, etc.?
>
> A while back I spent some time looking at the second problem. I believe
> that distributor machines can check this. It can be caused by an
> inaccurate cam lobe in the distributor or possibly inaccurate contacts
> in the cap. You can get some idea of the problem by checking the timing
> at both cylinders which fire at the same crankshaft position, e.g. 1 and
> 4 on the four cylinder. I've seen cases where the timing at these two
> cylinders were 2 or 3 degrees different.
> Larry
>
>
> Randall Young wrote:
>
>>>Do you use an old time distributor machine to test for spark scatter?
>>>
>>>
>>
>>No, I just watch the mark on the pulley dance under the timing light.
>>
>>
>>
>>>It is getting tough to find a shop that has one.
>>>
>>>
>>
>>I keep meaning to start watching eBay for one. I've heard they go
fairly
>>cheap and I'd like to have one.
>>
>>Randall
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