kalli

for some reason i was convinced heb has a 289 although he never stated it. what engine are we dealing with and how many estimated HP ?

Norm Peterson

2.25" is enough for a moderate 289/302. For 2.5" I'd want it to be behind nothing less than a fairly strong 331.

An X-pipe can actually help maintain smaller pipe sizes a little further up the displacement/power scale through better flow sharing (especially through the mufflers where most of the resistance/backpressure comes from anyway).


Norm

69FB

I have a modified 302 in my mustang and plan to eventually stroke it to at least a 331. Having said that when I had my exhaust re-done I went with 2.5" duals. I also drive a Honda Civic for my DD and I like a V-8 with a deeper throatier sound. I agree with Urban though use the J mandrel bent pipes if you go to a 3" exhaust.

Do not do like what I had on my mustang when I bought it. A "custom" 3" exhaust.







I would not recommend it. It is havoc on the whole exhaust system from the headers back.

urban_cowboy

69fb, that installation is terrible. Don't know that I have every seen pipes run under the axle tube .

It is not easy to fit 3" exhaust tight under a classic mustang, but it can be done and still run traction bars, subrames, and full length headers.

kalli

ahhhhhhhh !!!!! that hurts !!!!!!
what kinda plonker would run them straight under the axle ?

69FB

I really do not know. I guess that's why they called it "custom" b/c I've seen 3" exhaust but never run the way this is. My mechanic made the classic comment, "We cannot even put this on a traditional rack to inspect it further without tearing out the exhaust system."

It's the "quirks" that make these classic unique I guess.

zmetalmilitia

Couldn't you always dump the 3" in front of the rear tires or before the rear axle? May have to do that if one encounters clearance issues.

Oh yeah, I'd go 2.5", if your redoing the exhaust system.

68 Coupe

Urban,
welded J pipe...... is that a piece of exhaust tubing with a 90 deg bend that you weld in for areas like going over the axle, etc?. Where do you get these

jspagna1

Like Kalli said. But if you are running anything smaller than 2.25" I would definitley upgrade. Also 2.5" is pretty much as big as you can go on a 66' unless you dump them before the rearend which personally I don't like.

zmetalmilitia

I don't like that either. I hope I have the room on mine to run out the back.