I have a set of measuring calipers, sort of a micrometer in millimeters roughly. I had always been told the 3.0 had 1 7/8" exhaust stock exhaust size, so I went and checked my old stock exhaust sitting in the shed. The straight pipes are roughly 2 1/8" and in the bends it's roughly 1 7/8" (do to the pressure bends on the stock system). My borla system, which is all mandrel bent, is exactly 2", in the bends and straight sections obviously.

Now I've been told the stock 3.4 system is 2 1/4" all the way through, but pressure bent, so the bends are probably about 2" or so give or take.

But then I've heard the aftermarket exhaust systems for 3.4's are 2 1/2" mandrel bent.


Any input? The reason I ask is I'm looking at the idea of doing a swap but I want to see if my 2" borla mandrel bent exhaust will still be feasible to use with a 3.4, or if I'll need to bump up the size. I did notice a performance improvement in the 3.0 when I switched to the aftermarket system. This improvement would have come from the mandrel bends being less restrictive than the stock pressure bends, and the free-er flowing Borla muffler.

 

I had the Borla system on my truck for years, but I decided it was in my best interest to fab up a 2 1/2" system when I did my conversion. The Borla just didn't look like it was going to be a good idea, since it was smaller diameter than the stock 3.4 exhaust.

I used a pair of Magnaflow cats, and an 18" Magnaflow muffler on my system (all stainless), and I have been very satisfied with it for the 7,500 miles that I've driven it.

My exhaust cost me about $200, plus my fab time.