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Timing Light Question

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sultanoswing

sultanoswing

Jedi Hopeful
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At 600 rpm, my engine is a little rough, making the dynamic timing a little hard to judge as it's moving about by a few degrees.

Are there any values available for, say, 900 or more rpm's?

ps... this could be related to worn timing gear, I know.
 
HI Sultanoswing, I believe what you are seeing is a worn distributor if the timing is unsteady at idle. Raising the speed may stabilize it but you must know what the advance should be at that speed to check on the timing .However, it is not the most accurate method to use.---Fwiw---Keoke
 
Hi SOS,

I would agree with Brad on the timing. 30 degrees at 3000 rpm should be close to optimum.

The fact that the engine is "a little rough at 600 rpm" I take to mean that the rpm is varying slightly, as is the advance. This doesn't necessarily mean that something is worn. IF the rpm is rock steady, & the timing is varying, something IS worn. Especially if the timing is varying at 3000 rpm. If it isn't varying more than a degree or two at 3000, no problem.

The centrifugal advance is two stage. It advances a rather large amount for a given rpm change until the engine reaches somewhere around 2500 rpm, & then advances less for a given rpm above this point.

600 rpm is on the steep part of the advance curve (the advance changes quite a bit for small engine speed variations) & this is normal. Timing at a higher rpm puts it at a point on the advance curve where the amount of timing change vs rpm change is much less. Do make sure that any vacuum advance is disconnected when doing this timing check.
D
 
Thanks for your suggestions, guys...yes, it is the rpm which is a bit rough at 600 - and it is indeed this which is causing the variability in the advance.

The vacuum and centrifugal advances both check out as normal (without going into full and exact testing), so I'm happy the the dizzy itself is in pretty good nick.

I'm running on unleaded 98 RON, BTW, using 14 degrees advance @ 600rpm (or as near as I could average it without a special tach-sensing timing light). I'll compare her at 30 degrees @ 3000 to confirm - but she's already running better after today's adjustments.

SoS
 
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