So I’ve got a 91 LS with a B18B1 swap. I got my cat replaced last year and since then I would always hear/feel metal rattling right under my seat most of the time when I’m driviving or just idling. This is either cause the cat was slightly bigger than my old one so it rubs against the car (I also told the mechanic it was a 91, maybe I should’ve mentioned it had a 95 engine so the cat would’ve fit better? I don’t know.) , or it’s the exhaust pipe (near the cat) that rubs on the car after they welded it. So my question is… since its not the stock engine, is having a B18B1 resulting in the headers/cat/exhaust pipe to be off by a little that it rubs against the car? It’s really annoying having to hear that rattle every time I drive. Also, it’s not the rubber hangers, the cat or exhasut pipe literally rubs against my car. And thanks for reading all this! Haha
Even if you were to prove that fitment “should” be perfect, sounds like you need to have someone at an exhaust shop fix the problem either way.
B18a and b18b are physically identical, they will sit the exact same in our engine bay, as the mounts used will be the same.
Seems like they didn’t weld it correctly in the right spot. The only way to find out is to jack up the car and get under it and check it out.
Yeah, your engine has zero to do with your exhaust fitment issue. Could be something as simple as a loose heat shield…
Hmm I figured they’re identical, just thought maybe the headers placement could’ve been off a little compared to stock and since they connect to the cat and exhaust. I’ll get it looked at then. Thanks for all the input!
Well, yes… If the header/cat/midpipe are aftermarket, then indeed one or more of those pieces can throw off fitment…
But the MOTOR itself will sit the exact same, regardless.
Expecting aftermarket items to fit as good as OEM is a high expectation.
If you’re shoving bigger piping in the spot that smaller piping was meant to go, then naturally you will have fitment and clearance problems. As Colin said, it’s typically a vibration due to the heatshield.
Right. And yeah I’ll check into that, thanks.