Will the timing events inside the engine noticeably affect the ignition timing events going on as well? My current example is a cam setup as follows:

Intake Exhaust
Duration (.050): 243 243
Lobe Lift: .3883 .3883
Separation: 114*
Timing events (.050): Intake - Open: 13.5 Close: 49.5; Exhaust - Open: 61.5 Close: 1.5
Gross valve lift: .582 .582
Valve lash: .026 .026
Duration (.020): 276 276
Degree Intake lobe to 108

I was told at one time that degreeing the intake lobe to 108 was advancing the cam quite a bit. As I understand it, advancing the cam causes the valve timing events to all (equally) occur sooner than leaving the cam at a standard installed position. If the intake is closing sooner and exhaust is opening sooner, would that possibly explain why (for me) setting the timing conventionally safely (30-36* locked) leads to an exhaust after fire with acceptably lean air/fuel ratio at idle? Would a motor with such a cam profile installed at an advanced setting need more than conventional timing to function properly (38-42* locked before pulling for boost)?

Thanks for any input guys. I did not come across this type of thread searching and thought it might make for better discussion in this forum.

 

The camshaft drives the distributor thru a gear system.

If the camshaft is installed correctly in relation to the crankshaft, even though a intake lobe is advanced or retarded the Ignition only knows when the firing event occurs vs the crankshaft harmonic balancer TDC position and pointer.

So if the mechanical advance weights are kept from moving (by using heavy springs) and the vacuum advance diaphragm is disconnected if you want the ignition event to happen at 6 degrees before TDC then the timing light will show the 6 degree point on the indicator will match the harmonic balancer point once the distributor is turned to that setting. Whether the camshaft has a straight up intake lobe centerline or a 4 degree advanced camshaft lobe means nothing because you are only setting the distributor firing position in relation to the crankshaft not a camshaft event.

Both items, camshaft events and distributor firing events are stated in relation to the crankshaft position but are independent events.

If you had a mustang with variable camshaft timing you could have the ignition timing still be at 20 degrees before TDC and be moving the camshaft all over the place.

I hope this helps. What the engine "Likes" is a whole different discussion.

Tom V.