Saturday, December 27, 2014

Dual Exhaust System Removal

1967 Ford Mustang Fastback dual exhaust removal If you've been looking at the earlier pictures of the Mustang, you've no doubt noticed that it's generally in good shape, but everything on the bottom of the car is covered in decades of gunk. A lot of that gunk is from the slow leak of transmission fluid that was mixed with dirt and dust from from all those dirt roads in Colorado that the Previous Owner (PO) was driving on. As a result, the bottom of the floorpan and trunk, as well as the rear axle are in serious need of a degreasing and cleaning.

This also resulted in an exhaust system that, short of the exhaust manifolds attached to the engine themselves, is not worth saving. It's rusted through in several places, and the bends are more like kinks instead of mandrel-bent tubing that I want. Mandrel bends preserve the diameter of the tube through the entire bend, unlike a bent pipe which will pinch the pipe and introduce restrictions to the exhaust flow. Remember, an internal combustion engine is essentially a big air pump - unnecessary restrictions on the intake or exhaust side will reduce it's potential. 

The NPD paper parts catalogs have a great section that illustrates all the components of different exhaust systems of various years  The exhaust system appeared to be the correct dual exhaust system for use with a 1967 289 V-8, but the transverse muffler is date-coded from the early 1970's and the exhaust hangers at the back of the floor pan are just big lag screws forced through the floor pan (not the correct hangers I expected to find). These should be attached to a dual-bolt bracket that connects to a reinforcement plate inside the passenger cabin. I think this means that this was not actually a dual exhaust car from the factory - from what I have read, the reinforcement plates were installed at the factory for all dual exhaust cars. I find that confusing since all the other GT options are on the car (fog-lights, front disc brakes, etc.)  I will eventually install the correct reinforcement plates and use the correct hangers for a new dual exhaust system. Good Lady Wife has informed me that the car should have an exhaust note that is so loud and awesome that it'll wake the neighbors anytime it's fired up! As you wish, my love...

So, out comes the exhaust system. I removed the clutch Z-bar assembly in the engine bay to get at the left manifold bolts, but no luck. So I broke out my trusty Sawzall and cut the pipes. Even this is tricky as the saw was very awkward to get into position. And yes, I know it would have been easier to pull the rear axle first. This is, after all, my first rodeo.

Here's a shot of the rear end before the hammer (and Sawzall) came down:


There are hangers at the end of the floor pan that have to come out. I don't have a good shot of the hangers in place - it's a tight area to get into - so I'll just show you what it looked like after it's all out.

Drivers side - the two small holes are where the lag screws were holding the hanger. The big hole is where I removed the rear seat belt and found it was held in place by a few fender washers between the bracket and the floor. Yikes! It's a mess, no doubt, and there is some real metal work to be done here to get it back into shape.



And the passenger side - not a lot better. The holes on the right were where the hanger was connected - the large hole is for one of the seat belt brackets.  Notice the cracks in the floor (called the shock mounting reinforcement panel) and a bunch of screws that should not be there. Greasy, oily, spider-webbed, cracked and generally gross. Just another mess to fix.



There are also hangers at the end of the rear frame rails that come out. I just cut the rubber section on each one so I could control when it dropped out.



And that's about it. The system is really only held in at three locations - the exhaust manifolds, the rear floor pans and the rear frame rails. If the rear axle had been out I could have slide the entire thing out in one piece. Instead, I had to cut each set of pipes at the muffler and weasel each section out in pieces. This is fine is you're not keeping any of the old system.


The mistake I made here was getting in a hurry to recycle all this without cutting the exhaust tips off - they could have been reused, and that's an $80 mistake right there, and why I added the 'keep all old parts' commandment back in my earlier post.




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