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ASAP emergency: 107 exhaust

2K views 25 replies 5 participants last post by  unavita 
#1 ·
I found a '74 entire exhaust. It is without Cats. Will it work on my '80 from the manifold flange back or does it need the manifolds?
 
#5 ·
My exhaust is in great shape but the o2 sensor and the cats. I am wanting to get rid of the cats. I'm told I may want to keep the 02 sensor. The system I'm looking at has cherry bombs. I will probably replace them with another muffler.
 
#8 ·
the difference will be the end that connects to the manifold. the 74 should have a ball type exhaust pipe end that fits into a cup style manifold, and the 79 should be the opposite, cup style on the exhaust and ball style on the manifold if I recall correctly, but not 100 percent sure........
 
#16 ·
Believe it or not my manifold bolts came out without any issues. The problem I had was access. Raising the engine a bit helped. The small engine dampers make it hard to get the manifold off the studs on the right side. I haven't touched the left side. I have only loosened, but not removed the bolts attaching the downpipe to the manifold. I think if I try to remove mine I will be in trouble.
 
#22 ·
I don't know what increase of HP you might achieve, I know the engine will breath better, and with that will come a change in back pressure and may require an adjustment to the fuel/air mixture. You may experience a loss of low end performance from the loss of back pressure, but may pick up some fuel economy at cruise (this is all based on my experience with my Harley back in the day).

The main reason I dropped the cats was to gain clearance under the car. When it was federalized it seems they welded the cats to the exhaust, and really screwed it up. They hung down way tooooooo far. See the pics of before and after.
 

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#23 ·
Wow. Nice job. And yeah I see why you did that! What was labor on that?

On the back pressure I'm thinking if I leave everything 2 inches that will create enough back pressure! The 3 cats system is so restrictive. The 80 has lower compression to accomodate but I am still thinking that the change will be good for 20hp.
 
#24 · (Edited)
Did all the work myself, so it was FREE ............. LOL yea....took a week or so to complete..

I originally planned to swap the SLC system to the SL, but there were too many pieces cobbled together, and I couldn't get them to align properly. So I decided to just eliminate the cats............

I did modify the down tubes though.................. I cut mine off at the cats, took the ends off the SLC and had them welded to the end of the down tube.

Had the muffler shop make splice pipes to go from there to the center muffler....That way if I want to drop the exhaust, I don't have to fiddle with the O2 sensor...They flared the one end to couple to the ball end off the SLC style connection. Hope that makes sense.

I fixed the heat shields and re-secured them, blasted and painted the old exhaust pipes.

And no-one can see any of it.............. :(

p.s rowdie wasn't sure if the angle was the same, it appears it is close but not completely sure though.............last pic.............but the style of connector is different ..............
 

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#25 ·
Yeah those are great pics! Originally I was thinking of just using the driver side and H-pipe. The H-pipe could be modded to fit where the current Driver side goes into the passenger side. then I'd just ad a second mufller where the third cat is. I'd leave the o2 sensor intack.
 
#26 ·
Well a lot was learned today. First, my o2 sensor is fried so I've been driving the car without that working properly for a while.

Also, the exhaust system I am using to replace my '80 with will bolt right up.It's an SLC to SLC swap so that's good. The bolt's are spinning so I'll be cutting them out Monday.

So I will put a new O2 sensor with fouler plug in the new system after install.

There are 4 differences between the Euro version my mechanic, Dietmar, explained to me today: Cams, throttle body/ throttle positioning sensor, exhaust, compression ratio. That explains the 215 hp to 160 hp drop in my year from Euro to US.
 
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