I have a 3" muffler that I want to put on the express van which has a 2.75" exhaust system. I was looking for a band clamp that adapts for me, but I'm not finding one. The muffler is also shorter by about 8" so I was going to weld a piece of 3" tube onto the muffler so it's the same length as the stocker I'm cutting out.
It would help if I knew how exhausts were measured and the protocols for which end is which. Is my 2.75" ID or OD? Is the muffler (being 3" nominal) actually 3" ID so it slips over a 3" OD exhaust pipe?
If I just slide the 3" tubing over the 2.75" pipe in the van, will that be close enough that I can use a 2.75" band clamp. Does that make even make sense? I'm thinking that if the muffler is 3" ID, the extension tube I put on it is 3" OD, which means it's probably 2.875" ID or so. Can I just use that as my slip fit over the 2.75" factory stuff and use a 2.75" band clamp? I may have a cheapy tubing expander that you put on an impact. Maybe flare the stock stuff up to what I need to make it a slip fit?
I don't mind welding the extension on the muffler while it's on a bench, but without a lift I don't want to weld it on the van.
Pipe is measured by OD. Exhaust connector parts will usually specify ID or OD so you can do exactly what you're talking about, but assume OD unless told otherwise. Figure a roughly 1/16" wall, so you'll want a 1/8" step between ID and OD.
You can get band clamps with differing diameters, I have one on the Vanagon. Will this do what you need?
https://www.amazon.com/dp/B078TZCMX5?ref=ppx_yo2ov_dt_b_product_details&th=1
Thanks for the clarification. I wondered if it was like plumbing pipe where the nominal diameter describes neither the ID or the OD.
I'm not sure if that clamp will work. I assume that is for a slip-fit of a 3" ID to 3" OD pipe. If my factory stuff is 2.75" OD, and the smal end of that is designed to clamp on 3" OD, I doubt the clamp will compress enough to seal it. I need a clamp that will do 3" OD to 2.75" OD
It is OD until you get into much larger industrial sizes. IIRC the change is at 8" or so.
I found a bunch of those, and they might work as the extensions if they're long enough. That one is 3" ID to 2.75" ID, so it wouldn't fit the 3" ID muffler, but if I can get two of those long enough to weld on the muffler, I can just use that as my extension and two 2.75" clamps.
I think I need 3" OD to fit in the muffler, then some way to get to 2.75". I can weld to the muffler on the bench, but prefer clamps on the van.
I suppose I could 3" pipe out of the muffler, then two of those to make 2.75" slip fits, but that seems like an unnecessary number of weld joints.
L5wolvesf said:
https://www.autozone.com/loan-a-tools/loaner-tail-pipe-expander
I actually have a set of those.... somewhere... but it's been three interstate moves since I've seen them. I think that might be the cleanest way. Weld some 3" OD in the muffler, then expand my 2.75" stock stuff to 3" OD and then get some 3" band clamps.
edit: Or get some 2.75" extensions and expand them to 3" to fit in the muffler and get 2.75" clamps.
Curtis73 (Forum Supporter) said:
I found a bunch of those, and they might work as the extensions if they're long enough. That one is 3" ID to 2.75" ID, so it wouldn't fit the 3" ID muffler, but if I can get two of those long enough to weld on the muffler, I can just use that as my extension and two 2.75" clamps.
I think I need 3" OD to fit in the muffler, then some way to get to 2.75". I can weld to the muffler on the bench, but prefer clamps on the van.
I suppose I could 3" pipe out of the muffler, then two of those to make 2.75" slip fits, but that seems like an unnecessary number of weld joints.
I'd confirm the muffler is actually 3" ID, I'll bet it's 3" OD.
Curtis73 (Forum Supporter) said:
L5wolvesf said:
https://www.autozone.com/loan-a-tools/loaner-tail-pipe-expander
I actually have a set of those.... somewhere... but it's been three interstate moves since I've seen them. I think that might be the cleanest way.
once you buy a new one the old one will magically appear
kb58
SuperDork
6/17/22 6:48 p.m.
My impression is that Tubing is measured by OD, while Pipe is measured by ID. Everything I've seen seems to support that.
kb58
SuperDork
6/17/22 6:49 p.m.
L5wolvesf said:
Curtis73 (Forum Supporter) said:
L5wolvesf said:
https://www.autozone.com/loan-a-tools/loaner-tail-pipe-expander
I actually have a set of those.... somewhere... but it's been three interstate moves since I've seen them. I think that might be the cleanest way.
once you buy a new one the old one will magically appear
That's why, if it's inexpensive enough, I always buy more than one. That way, when I lose something on one side of the garage, I don't waste time looking for it and just grab the other.
There's also some variation between (cheap, Chinese) manufacturers.
I needed to make a tool to remove a jammed torque converter fitting from a Subaru transmission ( don't ask...please), and was advised to use a piece of 2 1/2" exhaust tubing. The piece from Advance Auto wouldn't fit, but the "same size" from Auto Zone fit perfectly.
In reply to Woody (Forum Supportum) :
I wouldn't trust the precise size of any exhaust mufflers or tubing without measuring it myself.
I just confirmed that the muffler is 3" ID, so it's evidently designed to be a slip fit over 3" OD tube, which makes sense.
Also confirmed that the tailpipe appears to be 3" OD, or at least close enough that a 3" nominal clamp should work. My vernier calipers are at work so I can't easily confirm what the diameter is at the muffler.
Assuming the tailpipe is one piece (which it appears to be, although it does disappear behind a shield) I should be good with a 3" slip fit band clamp (to go from the muffler's 3" ID to the tailpipe's 3" OD. Now I just need to measure the mid pipe to be sure.
Now that you have your IDs and ODs sorted, the monkey wrench is that it is USUALLY 16 gauge. Which makes some things convenient, the difference between ID and OD is 1/8", so you can do things like slip a 2" ID pipe into a 2 1/4 OD pipe.
I say usually, because I always made exhaust out of 14 gauge, which is slightly more expensive but bends nicer, lasts longer, and is quieter...
So I got impatient and went to work to grab my calipers.
Here's what I got.
I have no idea what GM was thinking with whatever that 2.923" midpipe. I measured it near the flange and further upstream and always got a similar number. That is closest to 2-15/16" which is close enough to 3" to make me think a 3" clamp would work. I could also stretch it out a hair if it doesn't want to clamp.
So does this below look like a plan to you? I gotta think that slip -over ends would be stronger than a butt connection.
