My Flowmaster Slimline Pipes Question

[GWL]

I’ve got my car at a welding shop for the adding of my Flowmaster Slimline Muffler to the original FFR stainless pipes.

My welder has not cut the pipes yet, he will today, but it looks like there is a difference in diameter from the FFR side pipes and the Flowmaster Slimline.

We both want him to be able to create a nice weld but what did you do to fill that gap?

Or maybe our rough measurements were off.

Any thoughts appreciated, George

[Florida Dave]

What is the difference? A small difference can be made up using intermediate sized exhaust tubing, a larger difference may need a bushing or spun adapter. Is the weld shop doing the work an exhaust shop or a multi-job weld shop?

[GWL]

Dave,

Multi purpose shop but has the experience and access to material. Was wondering what others have done. We are talking about an 1/8"(+-) all around.

George

[Florida Dave]

I can't speak for a roadster exhaust (yet), hopefully someone will chime in with pics of theirs. I would experiment with standard exhaust adapters to get a smooth flow of exhaust gas and the look I wanted.

Dave

[first time builder]

An exhaust shop would be able to swedge the pipe.

[rich grsc]

http://www.classicchambered.com/classic/products.html#cobra

[steno]

My slimline inside diameter was the right size for the FFR collector and tip to slide into place. Just tacked it, checked the fit and welded it up!

[GWL]

http://www.classicchambered.com/classic/products.html#cobra

Thanks Rich but I've got the Flowmasters already and it's being worked on today. Beside liking the design of this muffler I like the larger diameter which includes insulation, not to quiet the sound but to keep the outside of the muffler cooler. No snakebites with these!

George

[rich grsc]

George, how long have you had these? I just thought you might find a solution to the size difference by reading how these were installed.

[GWL]

George, how long have you had these? I just thought you might find a solution to the size difference by reading how these were installed.

Rich, Thanks, I've had them since they were first available. Remember, it has taken me 11 years to build this car and it goes to Jeff K. in early June for body and painting. I've got about 700 miles on it now. Still haven't got the low rpm in 1st, 2nd & 3rd smoothed out like I want it and it occasionally stalls with quick stopping but I've learned to keep it going with a blip of the side of my right foot on braking. I'm ready to get the Holley Sniper set up to both clean up my idle and stalling and to totally clean up the engine compartment.

George

[Avalanche325]

Mine were no issue. IIRC the sidepipe tubes can slide into the mufflers. I took mine to a place that specializes in fabbing up custom intakes and exhausts for turbos.

I made up a jig that held the parts exactly where I wanted them before I took it to the welding shop. I made my pipes a little longer than stock to put the outlet in line with where the rear fender flare starts. The factory pipes are a little short visually in my opinion. The FFR pipes (at least form a few years back) can be pretty crooked. The tips can also point at different angles. This is your chance to make changes if you want.

Make sure your guy can do finish work, not just make metal stick together.

[GWL]

Mine were no issue. IIRC the sidepipe tubes can slide into the mufflers. I took mine to a place that specializes in fabbing up custom intakes and exhausts for turbos.

I made up a jig that held the parts exactly where I wanted them before I took it to the welding shop. I made my pipes a little longer than stock to put the outlet in line with where the rear fender flare starts. The factory pipes are a little short visually in my opinion. The FFR pipes (at least form a few years back) can be pretty crooked. The tips can also point at different angles. This is your chance to make changes if you want.

Make sure your guy can do finish work, not just make metal stick together.

The measurements we made were rough without the pipes cut and still on the car. I'll be talking to him this evening to see how it went today. This is the first person that has taken a wrench/saw/or weld to this car in the 11 years I've been building it. I built this car entirely myself, including the engine and transmission. I just remembered that I did have a shop cut and bend some mirrored stainless steel.

I've seen his welds and they are 'beautiful'.

George

PS-this build took 11 years with four moves starting at Wareham, MA. I also finished building a house and rehabbed a cottage on Lake Champlain in Vermont. Actually changed it from a camp to a cottage.

[Hoooper]

Use an exhaust expander to take up the difference. I welded the FFR pipe to the muffler body itself after using a pipe expander to get my classic chambered exhaust to just barely slip inside the FFR pipe. Same went for the pipe to the tip.

[GWL]

Spoke with my fabricator this evening.

He's making up four large washer/rings to take up the space. He'll cut them out tomorrow morning with a water jet cutter. Already has the program written into the machine. He is also going to make some extra flanges to space the four pipe side pipe further away from the 'J' pipe and thus the body as the MasterFlow has a larger diameter and needs to sit further out from the body. He'll cut them on the water jet and already has that program written. It is a heavy muffler and we may add an extra support further toward the rear.

He also has the side pipes cut up and has the new muffler mocked into place waiting for the spacers and thicker flanges.

I'll follow up later with some pictures.

George

[Avalanche325]

I'm surprised that there is that much difference in diameter. Mine slipped in, but were certainly not lose enough to need a filler ring. It sounds like your guy has it under control. I hope they turn out great.

[wareaglescott]

Cant help you there as someone else did mine for me.

2 things. They are substantially heavier so have a good plan to support them. I have about 8500 miles on those mufflers. It may just be me but they sure seem substantially louder than when I first installed them. I am curious what others have experienced? (Not trying to hijack the thread but seemed relevant)

[GWL]

Cant help you there as someone else did mine for me.

2 things. They are substantially heavier so have a good plan to support them. I have about 8500 miles on those mufflers. It may just be me but they sure seem substantially louder than when I first installed them. I am curious what others have experienced? (Not trying to hijack the thread but seemed relevant)

Yes, they are very heavy. We are putting on another set of side supports toward the rear of the Slimline muffler. He is welding on two larger tabs to attach to the traditional hanger under the seats. One in the traditional position and another toward the rear of the muffler. There is another frame member similar to the one used for the front hanger, in the rear, which he will hang another support from and attach to the second tab welded on the muffler. I have had him make the tabs on the muffler larger to have more surface area against future cracks or failure of those tabs. I'll post pictures later.

I then will add the forward hanger modification, in front of the footboxes, to carry the end of the 'J' pipe where it goes into the side pipes.

My fabricator has made some real nice stainless steel spacers to get the side pipes further away from the body because of their larger diameter. He made a bunch from a water jet machine he has access to.

Again, I'll post some pictures later but his welds are beautiful.

Some of you have mentioned using an expander to get a better fit. He had considered that but decided not to because of the stress placed on the stainless steel pipe and then welding to it may cause cracks later. Proper support will help against future cracks too.

Increased sound?: These mufflers aren't supposed to be glass packs. There is insulation in the outer shell between the inner and outer muffler shell and I don't think the inner shell is perforated but if it is then yes that insulation can burn out over time. It is too late for me to do some looking inside my pipes anymore.

I'm supposed to pick up the car tomorrow afternoon when he is done polishing them.

George

[Avalanche325]

There are two perforated metal cones inside. I can't see how they could get louder. Unless your ears are healing from the glasspacks.