Mounting help on presilencer section of RB streetport exhaust on '85
 

I picked up a used RB streetport exhaust a couple of months ago and I'm finally getting around to installing it. I've got the old exhaust off (which gave me surprisingly little trouble), but I'm trying to puzzle out where the dual-presilencer section mounts on my '85.

The instructions on RB's web site say for 84-85, you should use the included 8mm x 35mm bolt supplied by them. There are two a studs on the presilencer towards the front of it close to the where the header bolts to. One of these is where this bolt is supposed to bolt into. But I can't for the life of me figure out what this bolt is supposed to attach to on the car. The rear hangs from the exhaust hanger by the rear wheel. The catback is simple. Just this one thing I'd like to sort out before I mount this thing tomorrow night. Anybody?

Also, it's looking like I'm going to have to remove the all of the heat shields from the car...does that sound fair?

fm

It looks like it's supposed to use the OEM catalyst hanger arrangement. The beefy triangle and pivoting link thing.

That stuff was long gone on my car, so i just used a piece of chain.

Attachment 668402

On my car I had to remove the heat shield, but could have and probably should have just trimmed it. I used some hardware store angle steel, S hooks, and donuts to replicate the big double hangar.
P.S. I had only the single pipe. Peejay's solution looks good to me. It only has to work, not win beauty contests.

Thanks guys...that helps. I'll crawl under again tonight and have a look. I'm not going to get bent out of shape if I have to rig something, as long as it works.

fm

I don't use any hanger there. I kept my heat shield with a little trimming.

I couldnt get my hanger to line up, so I dont use it either.

I like the chain idea, wouldnt have thought of that.

I don't have an aft presilencer hanger, just the over axle and rear hangers, and I am constantly fighting cracks in the pipe just aft of the muffler flange.

Coincidence? Maybe. But all that weight needs to be supported.

So much for these exhaust systems being bombproof :)

The chain is nice because it won't sag or crack but it will still allow for the pipe to grow with heat.

I do have an aft presilencer hanger and all muffler hangers are in good condition. I don't anticipate any cracking over here.

Man peejay, your pipes look pitted. You know the wall thickness aft of the muffler flange is only 14 gauge aluminized mild tubing until the collector which is actually SS. Or mine is anyway. Not much material to start with.

Get yourself an aft presilencer hanger (metal reinforced 84-85 kind).
http://www.mazdatrix.com/pictures/ex...-0300-N305.jpg
According to Mazdatrix these are no longer available. :(

Or make one! Just get something back there. The header up front supports the front half of the presilencers so a chain is not necessary. But the back half is at the mercy of how ever good your rubber hangers are, which tend to be dead most of the time; the upper one. The rears are probably all that's there anymore. That is not enough support for the kind of driving you do.

Well, I put on the exhaust with what I had. It'll do until I can get new hangers...I have determined that I am in need of 3 hangers. The front presilencer hanger has a spot to hang a donut on, but no donut is to be found. The aft presilencer hanger is shot...it is holding on the presilencer, but the rubber is worn completely through and the metal strap that encompasses the donut is the only thing olding the exhaust in place. Finally, the front muffler hanger is missing. It shouldn't be...I had it yesterday but I placed it somewhere in the garage and I can't find it :wallbash:

Anyway, yes, these are no longer available BUT I'm pretty sure you can make them. I got a Honda hanger which is just about the right size, but has no steel reinforcements. Then find the little steel shims in the right size (say, from McMaster-Carr), press them in, and you're good to go.

fm

The metal sags when hot. BTDT. Not supporting the mess is a great way to warp things and get gasket leaks.

My exhaust is (was) the old thickwall material with mild flanges. There's zero thinwall or stainless in the system. It's HEAVY :) As a rough guess, the midpipe and rear muffler each weigh roughly what a transmission does.

When I installed the exhaust, the car actually started to lean right instead of leaning left! :)

(and that's PART of why my car is such an overweight pig...)

the exhaust on peepers doesn't use all the hangers, and it seems to sag about an inch a track day...

I stand corrected about the chain in front. So add a chain in back. :)

As for the weight, I really doubt you've added the weight of two additional trannies to your car. The old systems were heavy, but I could still hold a presilencer center section with one hand. I can't do that with a tranny. The new center sections are LIGHT! Easily carry it with one hand in the middle.

I'm sure the muffler isn't as heavy as a tranny either. That's insane.

I dunno, it felt like it does when I one-hand a tranny.

Wait, that didn't sound right.

I blow so many trannies that I'm used to getting them off without jacking.

Err....