Hmmm, here are some questions about general exhaust installation with some photos to illustrate.

I have laid out the whole system roughly how it all fits together (I think!). Here is the front half:



Here is the catback:



Okay, here's the questions I have for the front part:

It comes with the exhaust manifold gaskets and the manifold -> y-pipe gaskets. However, it didn't include the bolts for the y-pipe flanges (on the MSA product image it has the bolts). Are there any special kinds of bolts and nuts I should be using or will anything work?



Next, one of the pipes on the Y-pipe is a slip on joint. How am I supposed to make this connection? Do I have to get it welded? Is there a proper rotational orientation to get this welded at or do I have to put it on first and fit it then get it welded? The latter would be problematic because this Z is the only car here. If i can get it welded before I take things apart that would be the best.



Okay, now onto the catback questions:

The center pipe to tail pipe connection doesn't fit. The tailpipe part is supposed to fit over the center pipe but it's a tiny bit off. I think the tailpipe might be a bit oval at the tip (maybe it got tossed around during shipping). Is there a good method to fixing this? It doesn't need much (just barely off).





Lastly, the system comes with 3 clamps. I assume that you want 1 clamp at the muffler to tailpipe connection, one clamp at the tailpipe to centerpipe connection, and the last clamp on the centerpipe to flange connection (the flange goes to the catalytic converter).

Here's an example of the clamp thing:



So how do I get the exhaust tip on? It slips on over the muffler. Do I have to get it welded or can I drill a hole to put a screw+nut to hold it?

Finally, are there any bolts/nuts that I need to get to replace the exhaust system? I know that some people replace the manifold studs, but I don't think you really have to unless you break a stud (correct me if I'm wrong!). Can I re-use the nuts/bolts for connecting the flanges at the catalytic converter?

Also, the factory service manual says to use an exhaust sealant at the connection between the centerpipe and the tailpipe. Any suggestions what to use?

Thanks!! Sorry for all the questions!!

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Justin
1986 Z31 NA 2+0

OK, lets' start with fitment:

1) I would use SS bolts of the proper size with lock washers, will be money well spent.

2) That y-pipe slip on joint won't be able to be welded until it is fitted up and on the car. It can be clamped, not necessary to weld and would facilitate an easy removal down the road (how's that clutch feelin? )

3) there is an expansion tool to open up the rearmost slip on. It costs less than $8 at Harbor Freight. Your other option is to take it to a local exhaust shop and have them "spread" it a bit for you. Costs could vary from nothing to $1,000,000 for that, best if you knew somebody.

4) a set screw or clamp on the tailpipe will work fine. Rotate the clamp so that the nuts are on the top, for aesthetic reasons.

5) I like to a use a very small amount of hi-temp red silicone on all the flanges w/ gaskets. Slip on areas are fine as-is, but a little smear might help it fit together a bit easier. NOTE* No sealant at all on the exhaust mani to head gaskets. If you need some of these gaskets PM me, I've got lots.

Time for the bad news: I really really really really am praying to the Z31 gods for you they have mercy on your wretched life and allow the exhaust studs to remain intact while removing the stock manifolds. Heat them all up with a propane/MAPP/acetylene torch, douche with PbBlaster or your favorite smelling penetrant. Repeat about 678 times and cross your fingers. I have only had one Z in over 20 that didn't break any studs.

Good luck to you sir

Totally agree on the manifold studs. Would change them every week if possible, to prevent them from rusting into place. I think you should EXPECT some (most) of them to break off in your hand. Buy an EaZy Out or a HeliCoil ahead of time ~ you're almost guaranteed to need to remove broken studs.

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1970 240Z

Thanks for the info Greg & Frank! Thanks a ton for clearing up the fitment questions. I found that I can rent an expander tool from my local autozone.... saves me a few bucks!

Is a U-bolt clamp appropriate for the Y-pipe slip on joint or is there a different type that I should buy?

Ouch on the manifold studs part! If you break a stud, how hard is it to remove? Aren't the clearances pretty tight in that area?

So with or without broken studs, I should replace them once the manifold is off, right? What would you recommend for replacements?

Luckily I am holding off for a bit on the manifold install. Catback and suspension are higher up on my priority list...

@Greg, the headers came with the manifold gaskets so I am set unless I break it or something crazy happens. I'll let you know if something comes up!

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Justin
1986 Z31 NA 2+0

u-bolt clamp is fine

How hard is it to remove a stud? Let's put it this way: I won't waste time trying to drill them out anymore, I literally just pull the heads off and bring them to a machine shop. This method may sound drastic but:

1) it is faster. Try drilling a stud out perfectly on center w/ a right angle drill w/ zero clearance. Lots of fun....fun like cancer of the eyeball.

2) easier. This ain't no L-series with everything right up fronty there for easy livin. I have had some success cleaning the area good and welding on a nut, but the odds of success that way aren't the best.

Skeered yet?

Having tapped & drilled about half a doZen manifold studs on EASY cars (Chevys, Healeys, motorcycles) and never got any of them perfectly "right", I fully agree with Greg. Take the heads to a machine shop to replace broken studs. They'll also clean out the holes (and lube them) and insert new studs.

That doesn't prevent you from taking the manifolds off yourself. If you snap one, hopefully it leaves you enough lateral room btwn the head and the fender to pull the old manifold off. If not, you'll have to pull the manifold as far as possible away from the head and get a SawZall in there to shorten the stud.

But be sure to soak all the studs thoroughly a day (or even two) before, with Break Free or similar deRuster before trying to turn them off. When you get the socket or wrench on them, tap the tool with a light hammer to break it free before torquing it off.

Hey ~ you might get lucky and not break any!

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1970 240Z

Quite skeered!

Why do these suckers break so often?? Does it happen when you are loosening them or when you are physically pulling the manifolds off?

If I don't break the studs are they easy to remove/replace? I have read that stainless steel LS6 studs are the way to go. Agree?

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Justin
1986 Z31 NA 2+0

The reason they are so hard to remove (and break so easily) is the thousands of times they get expanded/shrunk by heat & cold. That's the hottest part of your engine, and there are at least three different metals all bolted together there.

When a cold engine gets hot, all the metal expands. The manifold then swells and places more pull against the manifold bolts, stretching them slightly. The nuts are sometimes of different metal and don't expand at the same rate. They also fuse themselves onto the bolts, then rust on top of that!

When you successfully remove an old manifold bolt, you'll notice it appears slightly 'wasp waisted', or skinnier in the middle than on either end, and the threads in the skinny part will be visibly different than those at the ends. They appear "stretched" in the middle. It all started out identical, but years of swelling and stretching and cooling and shrinking have distorted the whole thing.

Now, you consider this 'wasp waisted' bolt, which has 'welded' itself into the threaded hole for 10(?) years, and welded itself into the retaining nut at your end, and you can see it doesn't want to move. Cover the whole mess with 10 years of rust, and it becomes pretty clear that nothing wants to come off. You come along and put 30-40-50 lbs of torque on your end, and what moves is not the nut, nor the seat of the bolt, but the skinny 'waist' of the bolt. It simply snaps in two.

(And if you haven't anticipated this sudden free-motion, your knuckles get skinned off. Then you get to try it 11 more times with bandages all over your hands).

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1970 240Z

Welllllll, I tried to take off the center pipe today.

All was well until I tried to take off the two 17mm bolts connecting the flange between the center pipe and the cat. The one on the driver's side wouldn't budge at all and the one of the passenger side broke.

Anyone have tips on what to do next?

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Justin
1986 Z31 NA 2+0

Yup. Try TIGHTENING the one which didn't move. We assume you have sprayed it with some kind of evil-smelling rust dissolver for the past 2 days or so, before trying to turn it off.

TAP the wrench with a lightweight hammer in both directions for a minute. The vibrations actually help break the rust free and give you a better shot at turning it off. Air impact wrenches work on that same principle.

If you have enough room, you can try squeeZing the flange tighter together. I have used a C-Clamp and/or a pair of Lockjaw pliers for this. That takes pressure off the bolt and *MAYBE* lets the nut turn.

You can also completely remove the broken bolt, replace it with a good one, then torque the daylights out of it. That will pull the clamp together, relieving pressure against the froZen bolt and *MAYBE* let you turn it off.

Turn the froZen bolt minutely both ways until you get a slight movement. Once you do, keep expanding it slightly in BOTH directions ~ tight/loose/tight/loose until it eventually turns off. Give it a chance to cool down occasionally ~ heat from friction softens & weakens metal and helps it to snap.

BUT ~ in every muffler shop I've ever visited, the pros simply cut the old bolts off with a SawZall or a torch. They never waste time trying to take them off by hand. You're gonna replace them with nice stainless boltz, anyway.

Frank

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1970 240Z

Yup I used good ole PBlaster... still no dice. The bolts looked pretty dang rusty on the outside.

I sort of gave up after I broke the bolt so I didn't really check... but is it easy to remove the broken part from the cat? I was thinking I could just punch it out with a hammer or something. If that's the case, is it worth it to, as you said, just cut or break the other bolt too?

Stainless steel replacement is definitely going to happen.

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Justin
1986 Z31 NA 2+0

Well, without seeing the cat I can't determine if it's held on with bolts or studs. If it's bolts, I'd personally probably just snap both of them off and be done with it ~ it would be a lot easier removing the broken parts when you have the cat on a bench.

If they're studs (like, sunk into the cat somehow) I might make more of an effort to save them. But even if you snap them off, you can often unscrew them by filing a cross-cut into the end of the stud, then using a fat screwdriver to simply turn it out. If that doesn't work, there are always EZOuts and Helicoils.

But don't be ashamed to take it to a shop and pay them $20 to remove & replace them. Every mechanic in every shop spends many hours each pay period drilling out rusted, broken bolts and studs. It's simply a part of the industry. They do it so many times a week it becomes easy for them. Don't let your fun project become a drag by wasting 10hrs on one or two obstinate bolts. This is supposed to be fun, remember?

I have to admit, and I've met a lot of good Z mechanics who feel the same, that putting new stuff on is far more fun than taking old stuff off. The new stuff is all clean and all the hardware turns on easily, and it looks all spiffy when you're done. Taking the old stuff off is a disgusting mess. Everything is rusted and flaky and you get rust flakes in your hair and eyes and nothing wants to turn off for you. A lot of guys just take a SawZall under the car and cut the old pipes ahead of and behind the cat, the muffler, etc and remove the whole system that way. Then if they want to save something to re-install it, they can put it in a vice and remove the rusty bolts with a saw or a torch or a chisel if necessary.

It's supposed to be fun. Let it be fun.

F

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1970 240Z

Youch, checked underneath today.... looks like they are threaded into the cat.

I heed your advice... will definitely take this to a shop!

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Justin
1986 Z31 NA 2+0

Wow, shops are quoting me at $90 - $100......

I could buy a magnaflow cat for that cost.... anyone have suggestions and/or a torch and a lift??

EDIT: Actually, I might just buy a small torch and try it myself.... I saw some videos of people using oxy-acetylene. Luckily on the broken bolt there is enough room on the back of the cat for a pair of lock pliers... Harbor freight has a small butane torch for $7. Think it'll be enough?
http://www.harborfreight.com/micro-torch-42099.html

There's also a propane one: http://www.harborfreight.com/electric-s ... 91061.html

EDIT #2: Borrowing a propane torch from work!

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Justin
1986 Z31 NA 2+0

Bammmm got it!

Tried the torch thing, but honestly the propane torch just didn't get hot enough. I think a MAPP or oxy-acetylene would have worked though.

I was able to actually get the front two bolts of the catalytic converter off without breaking them! I soaked with PBlaster and heated and cooled it with the propane torch with the hopes of sucking some of the penetrating oil in and breaking some of the rust up. In general though the front bolts weren't nearly as rusty as the rear ones. They came out alright. So then I just got a hacksaw and went crazy. I made one cut up near the cat to free it. I also made a cut near the part that goes over the suspension arm so I can get the muffler out.

Got the cat back to my lab where we have a sturdy bench vice. Put it in the vice and soaked the remaining bolt at the rear (the one I didn't break) in PBlaster and did the heating cooling thing again. Put the wrench on it... turned and the head snaps right off. Didn't even use a breaker bar!

Played with the torch and locking pliers or vicegrips for a little bit. Decided to just drill them out. I used a hacksaw + dremel to cut the studs flush. Centerpunch to mark the middle of the bolt. Then used a variety of drill bits with a two-hand high speed drill to get through. We have a drill press but the cat was too long for our mount. Right now I've got both holes free! Took a while but it was an experience! And saved some bucks.

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Justin
1986 Z31 NA 2+0