Jeff20B

iTrader: (13)

You guys all know how the RB dual pipe "streetport" system has a center section which contains two presilencers. Here's a picture to get the juices flowing.


I'm talking about the rear presilencer. It fits fine in that narrow section in front of the rearend.

The dimensions of the RB center section are 6" wide and 4" tall. The heat shield accommodates it well.

But I'm wondering CAN I GO BIGGER?

Now more juices are flowing.

I wanna build a 3" system for the '81.

I have several options for the cat location so that's taken care of. I also have several options for the main muffler location, so that's been handled nicely too.

But what about the narrow area right in front of the rear end? Can anything aftermarket fit there and flow like I want?

Let's see...

You see this RB "medium" universal presilencer?


It measures out at 6.25" Wide x 4.875" High x 15.75" Long. That's only a quarter inch wider than what we know fits fine. Hmm. It will probably squeak by. How about the height? 4.875" it is. That's a hair under 5", isn't it. I don't know, man. At least the length is fine.

While we're here, this looks like a nice 5" Magnaflow with a 3" core

Length is fine. Width is the same as height at 5". That's pretty tall for that area though, I think.

Has anyone tried to use a 5" tall muffler there before? Any success stories? Any speed bumps missing their tops?

Oh I have NO plans to lower my car but don't want to scratch over speed bumps, if I can help it.

There is one 4" round Magnaflow with a 3" core, here http://www.magnaflow.com/02product/s...e=main&id=8173 but I'm affraid with only 1/2" of muffling material, it may be inadequate on an NA.

Jeff20B

iTrader: (13)

By the way I already have the medium RB. It's a whole 1.75" longer than the above listed Magnaflows. Should I just use it?

j9fd3s

iTrader: (3)

i've been under mine recently.

the reason RB makes their system turn in toward the center is because of the front passenger side floor. to fit a 5" round thing off of their header, you need to turn in, and once you're in the trans tunnel there is suddenly TONS of room

you do have to make a turn at the rear axle to get back to the passenger side for the muffler, although if you're willing to have the rear muffler at an angle, the bend can be really small. oh actually i've gone under the axle, if you go over, the UP part can get you to the side too...

it'll vary with ride height a bit, but most of the muffler will probably be to the side of the driveshaft

Jeff20B

iTrader: (13)

Thanks for the info. Yeah I've got RB's "large" universal presilencer for right off the header.

I test fitted the medium presilencer under the car today and it is just a bit too big for my comfort level. It's too close to the driveshaft and sticks down too low. I'm pretty sure I'll need the 4" round Magnaflow. Looks like the link above is wrong so here it is corrected. http://www.magnaflow.com/02product/s...e=main&id=8188

I could probably make a 5" muffler work there, but I know of another project that needs an RB medium, which I'll post here soon.

84stock

iTrader: (5)

I am thinking of going with the roadrace exhaust with a dual in dual out magnaflow muffler.

trochoid

iTrader: (6)

The 3" round Magnaflow doesn't quiet the exhaust down much. I have one as a presilencer and an oval at the rear. The 14" oval will fit. The road race headers are shorter than the street ones so there will be plenty of room for it. I also have a 19" Borla but it won't fit because the RE headers are about the same length as the RB street headers. A 19" center/offset oval may fit the road race headers.

I have yet to figure out a way to do a dual 3" system. Just doesn't seem to be enough room and it will most likely hang too low.

Jeff20B

iTrader: (13)

Hey 84stock, how will your system compare to an RB primaflow/powerpulse muffler?

trochoid, I fortunately have access to a road race header so my next project is to build a 2 into 1. It will go dual 2" to a single 2.5" like an RB FC collected header, then it will expand along a length of 6" from 2.5" to 3". Then on to the RB "large" 3" universal presilencer, angled slightly toward the center so it fits right. Then angled back where the Magnaflow 4" round in the rear presilencer location before the rearend. Then over the rearend and into a 3" RB universal muffler. Then if it's still too loud I'll do a dual tip (chohakai suggested this).