I recently purchased one new coil from Auto Zone to trouble shot a problem with my engine. The coil is manufactured by Wells and before I installed it I checked the resistance between the secondares (the posts on top). It measured 8.74 while the old coils on the engine measured 6.65, 6.62 and 6.7. Does 8.7 seem high, has anyone else checked the resistance of new coils before they installed them? If I choose to replace all the coils should I buy another brand? Will the resistance of the new coil wear down with use? Will it affect my engine running one new coil and two old ones? Do I asked too many questions?

No, it sounds good. Diffrent manufacturers may vary the "turns" and ultimatly the Resistance a bit, but that resistance sounds good. That higher restance is small, but may result in stronger secondary due to a 'higher saturation point". When a resitance drops in a winding it is usaully caused by a breakdown of insulating material and effects resistance values. If that value drops enough, the output will drop porportionatly.

I have checked coils that tested 'good'. - Well in spec, however in operation they would not function properly. Once a load was introduced, the "short", or very low resistance had the effect of dropping secondary voltage beyond useable values. I guess what im trying to say is simply that coil readings can be misleading sometimes, so the ol eye test is a relevent one. If the spark is blue-white and snaps, I got a good coil. If its orange, chuck the coil............. :P