Stillen Throttle Body O-Rings
 

Hi all
I pulled my throttle bodies this morning to clean them and the O-rings look like they are falling apart (see attached photo). The entire Stillen system has only been in for about 15000 miles. Has anybody else noticed there O-rings looking like this? Side facing up in the pic, where the rubber is coming apart is on the throttle body side. Is Stillen using the wrong O-ring material for fuel?

I had the same thing, they're just cheap o-rings. You can order a box of 25 for like 9 dollars. I'm sure they seal fine when installed, just plan on replacing them every time you take the throttle bodies off.

https://www.mcmaster.com/4061T254/

DrBacon, you saved me some time. I was planning to measure up the O-rings and go right to McMaster-Carr as well. Thanks for providing that part number.

Some information for anyone who is interested:

So I did poking around McMaster's site and looked up the chemical compatibility for gasoline for the O-Rings they carry. So Buna-N has a rating of "good" when it comes to compatibility with gas however Viton has an "Excellent" rating for gasoline. I ordered a set of these Viton O-Rings, they are like $6.00 each O-ring versus $8.00 for a bag of 25 however the cost is worth it if they don't break apart like the Buna O-Rings. My concern with the Buna O-Rings is getting something that broke off sucked down into the engine. The Viton have a slightly stiffer durometer rating and I feel that will also help seal to the throttle body better as well. I currently have them on the car, no vacuum leaks around the O-ring; I guess we will see how they look after 20k miles but I know the Buna's looked like crap after less miles than that.

The throttle body and plastic intake manifold are dry.

There is no gasoline in these areas.

The injectors are located way down by the intake ports on the heads.

Unless you are spraying nitrous and fuel in the intake tract like me!

I understand that the O-rings do not come in direct contact with gasoline however I also know that O-rings don't come apart like this for no reason. Something is attacking them. I would picture fuel vapors from some of the recirculated gases or even just when the car is turned off....or maybe it is just the heat killing them but something is.

Just to reiterate, these O-rings we are talking are for the Stillen supercharger intake; the stock Nissan O-rings, for the plastic intake, are completely different.