[Guest]

Ok I need some opinions here. I am replacing my exhaust and have noticed that I can make a straight shot under my axle tubes without lowering the rest of the exhaust. I am using 3" exhaust and really would prefer to not have any unecessary bends in it especially the tight radius bends to get over the axle tubes. Is this a stupid thing to do? Is ground clearance the only concern? As always thanks for the feedback.

 

[66coupe289]

I would recommend against it. Remember when you go over dips, the back end of your car can go up in relation to the axle tube, thus your exhaust will hit the tube. Either run it up over the axle or turn it out so it exits in front of the rear wheels, ala 65 Shelbys.

Secondly, note how far up the body of the car goes in relation to the axle when you jack up the car with a floor jack. This is true even when you jack up the front of the car. You would certainly stress the exhaust and likely rip the hangers out unless you jacked the back up under the axle everytime and were very careful how you jacked up the front end.

 

[Billgear]

Jack your car up and take note of how far the rear axle drops down!

 

[camachinist]

Even with the pipes going over the rear, ground clearance is always an issue, especially with todays modern wheels and tires and lowered cars.

On the race car, because of groud clearance issues, I was forced to mount the mufflers standing on their sides, with the offset outlet being the "over-axle bend".....given the limited travel of the rear suspension, the idea worked well...

What kind of engine are you running which requires 3" exhaust? IME, only engines in the high 400 CID range making 1.5-up HP/CI really "require" that kind of exhaust system. A 2.5" system like I run on the race car is a small liability, performance-wise, but really insignificant in the larger picture.

 

[Dinosawnj]

I run mine under the axle (Panard bar and a few other goodies prohibit an over the axle setup). I have not had any issues with axle droop. Additionally, if the lowest point is under the axle, ground clearence is less of an issue as the wheel with lift the car over most bumps. I used an ovalated tube under the axle (it's only 2" wide but flows like a 4" tube. They're available from DrGas and other circle track suppliers).

Bob.

 

[Teebone]

Not a good idea..the exhaust is designed to move with the car..the rear axle moves independently..one of these days the two will meet and at the very least..you will rip out the hangers..and end up driving home dragging your exhaust system..another question I have is..why are you using a 3" pipe..last time I saw pipes that large was on a 350 Ford diesel pick-up

 

[Brightman]

If your car is lowered with stiff springs it might work fine for you. I did it with no problems http://proinspectors.com/mustang/page1/39.html prior to rebulding the car. Jack up your car and simply measure if there is room for the axle to move.
Good luck.

 

[Guest]

Pat,
In response to your question, I am running a 460 that will hopefully someday be in the 500hp range. I am curious about you race car and the side mounted mufflers. Aren't most mufflers wider than they are taller? Thanks again for the advice!
Micah

 

[camachinist]

If you take a look at some of the pictures on my race car page and imagine the mufflers mounted rotated perpendicular on their normal long axis and placed between the floorpan kick-up and the rear end housing, you'll get the picture...the mufflers are offset outlet Dynomax ST's....the pipe enters the muffler at floorpan level and then exits the muffler near the top of the kick-up, right below the shock mount crossmember. Remember, my car is back halved and the floor is a good deal higher inside the car to set the car down over the large tires...

Hope that makes sense!

 

[camachinist]

Forgot to add that a 460, especially a high revving one or one which will be stroked/bored out to over 500 inches, is an application which could use a larger exhaust system (3"). You might investigate a side outlet or undercar system (dumping in front of the rear axle) utilizing SuperTraps...