Replacing exhaust -- tips before starting?

[RJ80]

I'm going to be replacing my '79's stock 4-1 exhaust this weekend. Sourced a 49-state '79 4-2-1 manifold and downpipe, a test pipe to temporarily replace the leaky cat, and will finally be putting on the Stebro I've had laying around to replace the leaky Ansa unit. I will be reusing the center pipe between the rear exhaust and the three-bolt test pipe. I also have a new exhaust manifold gasket, manifold-to-downpipe gasket, two new rear muffler rubber mounts, and two new three-bolt flange gaskets for the new test pipe. Besides better flow from the manifold and hopefully a more aggressive exhaust note, I'm hoping that the install fixes the exhaust leak that is thought to be the primary cause of my backfire on decel, as well as the rattle my loose exhaust has at various rpms.

My question: I'm trying to avoid breaking any studs, rounding nuts, and shearing bolts. What's the best course of action to remove the old equipment? I was just planning to soak most of the bolts in PB Blaster tonight to make things easier when I start in the morning. Should I expect trouble? I am budgeting a full Saturday and Sunday, but hoping to get the job completed after just a full Saturday.

Thanks!

[mbouse]

IMO - the weakest point in your endeavor are the studs at the bottom of the exhaust manifold. if those studs on the NEW manifold are at all rusty or corroded... clean them before you attempt an install. if you over torque, or torque those studs at an angle in the installation... the chances of cracking that casting and loosing a stud are fairly good.

of course, the outgoing casting we are not concerned about. plenty of PB Blaster on those head studs/nuts and patience. if you accidently remove a stud from the head, don't fret. just be sure to get it back in the correct way (studs have short and long threads on one end or the other).

will you ever be ditching that dual plane intake and the 28/32 carburetor? if so, i'd be looking at ditching that EGR feed tube from your new exhaust manifold before i installed it, plugging the hole left behind, of course.

[RJ80]

Mike,

Thanks for the quick response. Hadn't considered the studs for the downpipe... I'll be sure to clean 'em up before starting! With regards to the EGR system, I'm keeping it for the time being. I do have a 34 ADF and a single-plane intake manifold, but living in CA, I haven't quite decided what I'm doing with all that yet. Might just put the ADF on the dual-plane and keep the emissions junk. Or I might install the 1800 manifold along with an earlier EGR system, if I can source one. Got a little over a year before it needs to pass the sniffer again (Jan. 2011). That's actually why I specifically waited to find a '79 4-2-1 setup, so I could keep the EGR functional if need be.

[azygoustoyou]

When you do your install, If you haven't already, add another bracket to hold the exhaust up by the resonator. It will take the stress off the center. I believe IAP has a tech bulletin on the issue.

[RJ80]

Update:

Got the old exhaust off with minimal effort. Luckily none of the bolts were too difficult to remove. Slipping the 4-1 exhaust manifold around the water pipe was a nightmare, but finally got it off. After grinding down the side of the mounting flange on the new 4-2-1 manifold to make it fit easier around the water pipe, that went on too. Then the downpipe. The terminal problem for the weekend is that the Stebro exhaust I bought has a significantly larger (maybe 2-in.) inlet than the stock center pipe. Is it possible to shim that out? It's pretty thick stainless, so I don't even know if it was designed to use a clamp or not. I then tried to install another Ansa system that I had laying around, but the inlet on that seemed to be the same diameter as the downpipe, making it impossible to slip one in the other. Is this something best left to a muffler shop at this point?

Starting the car up with just a manifold and downpipe to move it in the driveway slightly, I noticed there was also a bit of exhaust leaking from around the downpipe to manifold connection -- guess that needs to get tightened up. I'm done for the weekend, will resume next week. The car's at a friend's house right now so I'd like to get it finished sooner rather than later. Any tips on either making the Ansa or Stebro fit properly?

[azygoustoyou]

I talked to a muffler shop about getting the header and the center section together. They told me they couldn't expand the one end to make it fit because it would probably split. They said to buy and extension that would fit over both and weld or clamp it together. I haven't done it yet since the car is on a rotisserie. I asked them what they would do and they said they would weld it over one end. Good luck and let us know what you come up with.

[RJ80]

I think that's probably what it's going to come down to... getting a short transitional piece and joining the two different diameters together with it. I'm going to the muffler shop tomorrow and will see if they can weld the muffler end of the transition, then I'll clamp the other end to the center pipe after I get it positioned correctly on the car.

I'll update tomorrow, when hopefully my car will be back home safe in its garage, rather than sitting in my buddy's driveway twenty miles away.

[azygoustoyou]

Either way you weld the transition piece. I think the header should go inside the center section for better air flow. Can you show a pic of the fix?

[RJ80]

Well, the header itself isn't going inside. my setup is the 4-2 manifold to the 2-1 downpipe which terminates in a three-bolt flange to a test pipe or cat. on the other side of that is another three bolt flange going to the center pipe, then the rear muffler sits behind that. I just need a slip-on transition between the rear muffler and existing center pipe to accommodate the .25" diameter difference between the two.

Hopefully both ends of the transition won't need to be welded in order to do that... If I have the transition welded to the rear exhaust, I can fit the system, slip the other transition end over the center pipe, and just use some exhaust paste and clamp to secure it.

[mbouse]

ummm... there is no pipe between the cat and the resonator pipe.

if you have a quarter inch gap there, then loosen the rest of your connections and squeeze the two together... then retighten everything once assembled.

[RJ80]

Mike, guess I was unclear on a couple points. First, yes, of course a single center pipe between rear exhaust and cat. Second, the gap is in the diameter of the rear exhaust versus the center pipe, not the distance between the two.

[mbouse]

a-ha !! quite a different colored horse all together. lots of D.I.Y. places sell diameter reducing pipes. that should not be difficult to find.

my stainless steel muffler from Fun/Imported came with a reducing fitting for the stock resonator.

[RJ80]

I just wanted to wrap this little saga up for the time being by thanking everyone for their constructive input and telling you all how things turned out. I took my rear section and center section to a highly-recommended local exhaust shop. Explained the situation, and the man running the shop said he could just expand the center pipe to fit the larger rear section. An hour or so later, I returned to the shop and the deed had been done. He said that the pipe split near the tip as he was expanding it, but he did a nice job welding it all up. He threw in an exhaust clamp to tighten the whole deal up and $10 later I was on my way back to the car to finish the job.

After quite a bit of clamp-tightening, I got the Stebro hooked up to the center pipe, used new rear exhaust hangers from Vicks, and bolted the whole assembly up. The Stebro fit is pretty good, if not perfect. I bolted in a test pipe to temporarily replace my cracked catalytic converter and tightened up all the manifold-to-downpipe connections -- they were a little loose. Dropped it off the stands, fired it up, and the Stebro sounds great -- much deeper and slightly louder than the Ansa. It really growls! The test-pipe appears to be something of a slight resonator too, and there is no resonator currently in my center pipe. The car also appears to rev slightly freer with the new system (including a '79 4-2-1 downpipe and manifold, mind you). I'm very happy with the way things turned out.

Next up -- swapping the anemic 28/32 carb (and possibly the intake manifold) for a 34 ADF. Stay tuned...

[azygoustoyou]

Good job! He did that for you pretty cheap. I had a muffler shop expand a straight pipe with their machine and he charged me $15 bucks.