Alldodge what is the reason for shunting the engine? I can't seem to fully grasp the concept.
From research when using the shunt tool this takes the timing to 0' however on removing the tool this puts it back to what it was? So what happens here plug the tool in then advance the timing to 8' on TDC then remove the shunt tool, it goes back to it's preset or the new settings?
Finally is the shunt tool necessary? Unless rebuilding the engine can the timing not be read and adjusted with a timing light without?
Thanks
the actual running timing is 100% controlled by the electronic module in the distributor. What you are setting (and needs to be set) is the "base (sometimes called static) timing" which gives the distributor module a known point to advance and retard the timing from. It runs on electronic tables in its silicon memory, and needs that known place to be correct. If for instance the distributor is set at say 6* before as a static, and the computer adds another 6* to that at idle, it may well be out of time, and a good bit advanced. With base (static) timing set to 0*, you would still get that same 6* advance from the module, setting you at 6* total timing advance, which is closer to correct (these are my OMC numbers of the top of my head for example only....) putting in the shunt tells the module that you are setting base (static) timing, and it disables any advance that it would normally add to the system. the shunt is for setting the base (static) timing only, and needs to be removed after that procedure.
IIRC, the module only has two failure modes... No spark, and NO ADVANCE.... so that may need to be checked as well, usually by disconnecting the shunt with your timing light still attached, and revving the engine slightly, and ensuring that the timing mark "moves" relative to the timing pointer with the light (do not adjust based on this, just making sure the module is doing its part....)
