OK, heres the deal. i went to put the new muffler on the diesel this afternoon, and all the pipes after it are on their last legs. instead of making a new y pipe for the stacks, i was thinking of just making a t pipe, cause it will be about $40 cheaper.
here lies the problem/question. i am not a good thinking fabricator. i can make it if someone shows me how to do it, but can not lay it out.

how can i cut a 3 inch pipe to fit flush with the side of another 3 inch pipe?
i know there is a grinder type tool specially made for this kind of thing, but i only have a set of torches, a plasma cutter and a MIG welder at home.

 

For an exhaust you want a Y otherwise it acts as a restriction and does not flow right.

There is a method to develop patterns for this type of thing using pencil and paper along with dividers or a compass that can be learned in drafting class. You may even be able to find the method described somewhere on the web but most of the references for the method refer to drafting, welding, or sheet metal classes, and books.

Otherwise grab a couple tin cans, cardboard tubes, or paper tubes, and start trimming them to fit and then split them for a pattern. You can also look at the HVAC vent fittings in the local home box store, buy one, and take the fitting apart for a pattern.

 

Do you have good drill? You can get a drum type grinder the size of the pipe.
If the pipe is to be 3", make 4 marks equally around the edge. at opposite marks, measure up the pipe from the end 1 1/2 ". Then make a arc from this mark to the other mark at the edge so you have two opposite half moons. here is your rough guideline. Use the plasma cutter to cut on the marks, then get the drum type grinder to clean up the cut.
what about this kind of split?

 

well eric, there is no real problem with restriction, cause it goes from 3 inch single pipe to twin 3 inch out to the stacks.
this is what i have now, but it is expensive to duplicate.

http://i41.photobucket.com/albums/e261/tjctransport/pipe.jpg

 

Actually that is not hard to duplicate. Get two 3" 90° bends from the parts store or muffler shop. Prop them up at 90° and mark both of them with a marker taped down to a block of wood. Cut them off roughly with a hacksaw or sawzall then hit them with a belt sander or grinder. Put them together around a 3" inside to 3" outside pipe adapter if needed (depending on what type of bends you get) and weld them up! A couple hours work.

 

yea, i know, that is how i made that setup. but the 4 elbows to make that setup are $42.
if i make it a "T" pipe, it will not cost anything, cause i already have 9 ft of thick wall 3 inch inner diameter pipe, and i can use the good parts of the existing setup to finish the exhaust.
the reason there will be no restriction is this is all after the muffler, and it goes into 4 inch within 14 inches of the splitter.

 

Oh, is that all?

 

the interruption to flow is what causes the restriction, the size doesn't help it. Dumping stright into a pipe with no gentle curve causes a lot of turbulence, which will cause backpressure.You would be better sreved cutting the end of the pipe at an angle, say 45, matching and sealing it to the lead pipe, then cut another 45 at the back, roll the pipe over, and reweld back into place, giving it redirection rather than turbulence.

 

if you have 3inch pipe find a 3inch hole saw drill threw about a 1/4inch from the end of the pipe thats goin to be the leg of the T the 1/4 inch will be enuff to hold the bit from walkin. the hole saw will cutt the correct u-shape to weld to the top of the T. the hole saw will also make the hole in the top of the T so when ya weld them together there wont be a big pipe hitin a smaller hole.im ilke you cheap is good if it works it might not be the best for performance but heck its cheap!! or free! thats the best rite there

 

perfect!! that is the kind of thing i would never have thought about.

 

Or to go redneck simple. go to lowes or home depot and get a cast iron "T" pipe fitting that the pipes will fit into, shove the pipes into the three ends, weld. Whalaa!

 

Sounds like the old redneck cutout valve...

Seriously, I only see 2 elbows in your picture. You can do things right or the expensive way. Exhaust restrictions like a T fitting will cost you every time you visit the pump. It is called being penny wise and pound foolish.

 

take 2 90* bent tubes. put them side by side to form a backwards L and an L. together it'll look like an upside down T. Now, cut about an inch off both from the top of the L down... it should taper off about an inch before the bend. then weld together. can prob email a pic of it on my grand prix. its what a custom shop around here does...after all you're not in any races right? and if its dual its really not that restrictive at all - keep in mind the engine needs SOME restriction if you want to keep fuel economy.

 

Not really, the old restriction myth comes from the fact that small tube headers worked better than large tube headers in a daily driver. Restriction didn't enter in, it was all gas velocity and scavenging effects.

 

Tom,

Considering I live 10 minutes away I'm surprised you didn't call me.

Anyway, the way to join pipes in a Y or a T is to fishmouth them. One does this using a pipe notcher in a drill press with some bi-metal hole saws (both I have and happy to loan you), or you can sharpie up some cut lines and use your plasma cutter to make the mating pieces.

Once cut with whatever method, you simply weld them together.

I'm home today (Monday) so if you want a hand during my usual window, call the house and I'd be happy to pop buy and help you with this. I've made a ton of Y-pipes over the years and it's not very difficult at all, especially considering the tools you have available to you.

You really don't want to make a "T" pipe as that will hurt your flow, lower your mileage, and cause you other grief. Especially considering how easy a "Y" pipe is to make.

One can make a true Y or a \| or a |/ as well. Just a matter of cutting the tubing the right way and welding it together.

We can even make a double Y and the spare leg can have a plate bolted to it as an exhaust cutout for days you want to be loud

If you need to make "bends" and don't have access to a tubing bender, you can make bends the same way I made my turbo manifolds - cut the tubing into trapazoidal sections and weld together. Not as smooth as a true bend but generally good enough for most purposes and by far better than a purchased, tight radius 90 degree piece.

The easiest "Y" to make is to slide two sections of pipe at an angle, lengthwise, through a bandsaw and weld the cuts together, giving you a 2 into 1 pipe. Then bandsaw the tail at the right spot, so the ID is the same as the mating tubing, then weld on a short extension piece and you have a "Y" pipe.