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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