I'm installing my MSD cap/rotor kit but the two o-rings are different... which goes where?

Does the rounded one go on the opti base and the "square" o-ring go b/w the cap and isolator?

 

You only use one of them. The round one is the old style and the square one is the new kind because people were having problems with the round staying in place. This would cause the rotor to rub on the cap. That being said, use the square one.

 

So it looks like they give you 3... 2 rounded ones, and 1 square one.

Based on the instructions, and what you and MSD told me ( I called)..

You place one of the rounded ones on the aluminum opti housing, then put the isolator on. You put the square ring on the isolator, then put the cap on that.

Don't use one of the round ones.

 

Scratch that... looks like you place the square one on the aluminum opti base as that's where the round one seems to want to split off. The square one seems loose on the base but once you put the isolator on it tightens up. The round one seems to work well under the cap, don't see where it will roll off.

 

You would be much better off with a stock one. I had the MSD cap and rotor and the rotor chewed it way into the cap and left me stranded.

I will never buy another one, ac delco all the way.

 

I heard most of those problems were due to installation issues with the o-ring. I can't see a properly installed cap/rotor having the same issues.

Mine seems fine, running great, except the high RPM miss I'm chasing isn't gone.

 

I've been running mine for over 20k miles. I am going to agree with Javier and say yours sounds like an installation error.

 

Let me know what you end up finding Javier, I installed an MSD Cap/Rotor
last week and it ran fine for a few starts. Then it started running ultra-rich
and breaking up around 3000rpm. I later found threads describing issues with
the rotor rubbing the deck due to the Oring. I'll be pulling it off this week
once it stops raining outside.

Very frustrating, since the new motor is running perfectly otherwise.

 

I know it was installed right, the only thing I did different was that I used the round o-ring instead of the square one.