A local shop recently replaced my stock cap and rotor with the MSD kit. I just noticed that they drilled into my intake elbow and ran a small vacuum hose, like how you would for a vented opti. Only thing is, I've got a 94, so it's a non-vented opti.... Did they screw up or is this normal for the MSD kits? My car recently started having idle surging issues again, so I'm wondering if this might be creating a vacuum leak.

 

there could be a vacuum leak but that is a normal install. the 95 and later cap can be put on 93-94's the difference is on the back end. actually they did the right thing because having that vaccum on the opti is a good idea

 

Okay, after weeks of trying to diagnose the surging problem, I came back to the MSD optional vacuum lines. I clamped the line connected to the intake elbow, and sure enough it cured the surge completely! The next thing I need to do is take off the vacuum lines completely. However, I'm not sure what to do with the open inlets on the distributor afterwards. Are they supposed to be capped, or can I just leave them open?

 

I had mine caped of until I got rid of it all together (LTCC). It seemed to be fine. To me if its sealed it better, unless you have a sealed vacuum like on the stock 95+ LT1. you could just do the vacuum part of the 95 conversion.

 

Thanks for the response. Anyone else have experience with the MSD cap and rotor? Am I supposed to cover the vacuum inlets when not in use?

 

You should not be having any issues if the shop installed the hoses correctly. There is a vacuum reducer and filter on the vacuum source hose to the intake manifold. If you remove and cap off the MSD, you are losing out on one of the benefits of the product.

 

You mention running a vacuum line to the elbow. That isn't a "vacuum" location.... the elbow is close to atmospheric pressure most of the time (tiny vacuum at WOT). Does the cap have a second nipple that is open (allowing dirty air in) or that needs to be connected to a vacuum source on the intake manifold (like its supposed to be)?

Sealed is not better, because the vent was added to remove the ozone that forms when there is a high voltage discharge. Ozone is extremely corrosive, and I suppect the cause of the blue corrosion that many people find at the harness connection.