What happens if you install a new cap/rotor/distributor assembly w/out the metal heat-shield that goes inside? Talking about the one that looks like a stove under-burner insert and matches closely one of the plastic Opti covers. Does it serve an important function (as it's name hints) - enough to affect performance when car is fully warm?

 

its funny that you ask becasue I almost forgot to re-install mine last night when I was putting it together.. Did you do the same?

 

I don't think it has anything to do with heat. It's like a moisture deal or something.

 

It might have been an attempt to isolate the optical sensor from the ozone generated by the spark at the rotor/cap interface. Or to keep any dust generated in the cap away from the optical sensor. I'd keep it. On a vented unit it would keep the air supply on one side (optical sensor), and the vacuum on the other side (cap), making the air flow out of the optical section, into the cap. That would support the idea that it minimizes dust and ozone contamination of the optical sensor.