Originally Posted by sam-missle
Valve timing is valve timing, ignition timing is ignition. the dist. is driven off the cam gear only. you rotate the dist. around the driven shaft to set the ign. timing relative to TDC. Has nothing to do with valve timing. if that were the case millions of vehicles would have messed up ignitions, as most engines have timing chain or belt tensioners on them.
millions of cars (old ones) do have misadjusted ignition timing.
When you phase the cam in and out with relation to TDC of the crank the ignition timing changes along with it as it is driven off of the back of the cam. If your cam timing changes under acceleration then if the distributor is driven off the back of the cam, it will change too.
This is also a reason for a lot of spark scatter on older worn SBC engines.