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Ignition timing

luhrs_40

Contributing Member
89 crusader 454 port side every 100 hours or so the timing advances it selve
without the distributor bolt been loose
From 10 deg to around 16
i use the boat as a charter and put around 300 hours per season
I checked the weights and springs in the prestolite distributor and seem ok
Can it be the gears on the distributor worn out? timing chain loose ?
engine has over 4000 hours but runs great good compression and dont use any oil
 
Gears wear and chains stretch, especially given high operating hours... but those effects are unilateral....

Are the points still in the distributor?
 
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89 crusader 454 port side every 100 hours or so the timing advances it selve
without the distributor bolt been loose
From 10 deg to around 16
The camshaft is likely chain/sprocket driven. A worn chain will not cause what you describe.
The two gears (the cam's drive gear and the distributor's driven gear) cannot possible wear enough to cause this, and if they were able to, it would retard the ignition, not advance it.



i use the boat as a charter and put around 300 hours per season
I checked the weights and springs in the prestolite distributor and seem ok
If the flyweight system was failing (as in the governing springs became weak from rust/corrosion), you may see an early advance, but you would also notice what's referred to as "bucking" during start up. (bucking, as in an early BASE advance that wants to push the piston back down before it crowns over TDC)

Can it be the gears on the distributor worn out? timing chain loose ?
Highly unlikely!
You would see other issues as well.


Are the points still in the distributor?
no they been replace with electronic module

By chance is this a Pertronix conversion?
If so, the magnet embedded triggering wheel is placed over the points cam, and will generally fit tightly.
The advance is still provided by the flyweight system.

If the flyweights are able to move freely, and if the governing springs are OK and are doing their job, the system should advance as RPM increase, and it should return to BASE advance as RPM decrease, and it should do this consistently time after time.


This leaves a lose distributor housing "clamp bolt" as the most likely suspect!



Summary:

Crankshaft drives camshaft and in sync.
Camshaft drives distributor and in sync.
Distributor drives flyweight system and in sync.
Flyweight system drives triggering unit and in sync with the advancing aspect of it.





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