DIY tutorial : making a merge pipe

[TomServo]

Okay, so I put together a little tutorial on how to make a simple merge pipe with basic tools.  All the tools I used in this are:
Bucket of water that your length of pipe can fit in long ways
Food coloring
Sharpie
Hand File(half round)
4.5" Milwaulkee angle grinder with a cutoff disc and a 60 grit flap disc
Paper towels
Millermatic 185 MIG welder
Posterboard/cardboard and scissors


For materials, I bought some flowmaster header reducer cones, part # R3530.  Heres a link to summit:
http://store.summitracing.com/partdetail.asp?autofilter=1&part=FLO%2DR3530&N=4294923429+4294838977+4294865471+4294791234+4294895342+115&autoview=sku
The goal here is to make a single 3.5" downpipe split into two 3" exhaust pipes.  This method will work for any pipe sizes/transitions, even just using two pieces of straight pipe to make a merge, such as single 2.5" into dual 2.5" for a header crossover.  As long as what you're merging is symmetrical, this will work.

One note before we get started, I don't know how well this will work on different materials.  It seems like it doesn't work so well on rough surfaces, the food coloring seems to seep in and not wash off nicely.  I used aluminized exhaust tubing, which is very smooth and clean, and it worked extremely well.  If it isn't working on the piece of metal you're using, perhaps try waxing the piece to get a smooth finish.

Lets get started!
Start by marking the centerline of one of the pipes on the end which is going to be the single part of the merge - the 3.5" side in my case.  Mark on the inside and the outside!  Makes it much easier to see.


Now, put a drop of food coloring on the pipe near one of your c/l marks.  I used the darkest color in my food coloring set, which is blue.  It still didn't come out very dark, so I somewhat doubt yellow or red would work very well.  Just pick the darkest that you have.


Now, use a folded up paper towel to smear the food coloring around on the pipe.  Keep working it until any bubbles of liquid are gone, just colored pipe left.  The paper towel will soak up a lot of the first drop or two, consecutive drops will go a lot further.  You can also use the towel like a felt marker after a few.  It only took me 3 drops to color nearly half of the pipe, which is more than enough.


Make a 'U' shape going from one centerline to the other, and touching the opposite edge at the bottom of the U.  Here you can see half of the U.  It doesn't seem very dark, but it still shows up well.


Now the tricky part.  Hold your pipe sideways by the edges, so your centerline marks are parallel to the ground.  If your finger holding the pipe is 12 o'clock, your centerline marks should be 3 and 9 o'clock.  Very carefully lower your pipe into your bucket of water to the centerline marks of your pipe, and approximately 3/4's of the way down the pipe.  You have to be very steady and pay attention to all sides of your pipe at once.  I find its easiest to first lower your centerline marked side into the water at a steep angle(like a 60* angle, so very little of the pipe is submerged), then hold that side steady and slowly lower the angle of the pipe with your other hand until you get 3/4s of the length of the pipe submerged.  Hard to explain, but you should understand with some pictures...

Fresh out of the water.. this one I messed up as you can tell...


Once you get it out of the water, carefully blot the drips off, do not wipe!  Keep the pipe in the same position it was in the water otherwise the drops will run across the pipe and ruin the line.  Once it is dry, it should look like this:



Although it isn't the easiest thing in the world to get the perfect line, it is extremely easy to re-do it!  If you mess up, just wipe the water off, add a drop of food coloring and recolor it.  It takes 30 seconds to color it.  I did it 3 times before I got a line I was happy with.  Still only took me 3 minutes to do.

Now, our line is there and fairly visible, but it isn't near dark enough for me to see while grinding on it.  So I took a sharpie and traced the line very carefully.  Sorry, don't have a picture of that...

I then took my grinder with a cutoff wheel and started cutting.  I cut each side down from my centerline marks to about 1" from the bottom of the U, where it gets real tight.  Too tight to make the curve with the cutoff wheel straight up.  For the bottom of the U, I lay the grinder down almost parallel with the pipe and make the cut.  When making a cut like this your cut line gets VERY wide, so don't just leave room for a kerf that is the thickness of the blade!  I cut so the tip of my wheel was about 1/4" in from the line(that I could see) and when I was done, the cut was just about right on the line.
Here is how pipe #1 looked after being cut, laid on the ground to check for flatness:

Not bad, I messed up the top a little bit.  I think what I did is when I rocked the piece in the water to get the line for the bottom of the U, I accidentally lifted the top about 1/8", giving a slightly curved line.  Nothing a little grinding can't fix.

The other side is a bit better.  Just a little work to do here.

Use your file to fine tune and deburr the edges.  Over the past few months I've grown to love my hand files, they're now an everyday tool for me.

Unfortunately, I got lazy with taking pictures so there aren't any for this section.  Its pretty simple, though.  I'll get some pics of my templates in a few.
Now that side #1 is completed, we can move on to the other side.  In order to get a perfect mirror image, use a piece of cardboard to get the imprint of the cut line.  I used posterboard, which is somewhat flimsy.  I'd use corrugated cardboard in the future.  Put the cut pipe in a clamp with the cut side up.  Place your posterboard/cardboard on top of it, and press down with your fingers to trace the cut edge.  Remove the cardboard, and mark with a sharpie the top two corners.  Use your scissors to cut along the imprinted line, flaring outwards once you get to your edge marks.

Now, lay this template over your second, uncut piece.  Line up the edge sharpie marks you made with the top of the pipe.  Position it so it has no gaps anywhere around the cardboard.  Try to keep it perfectly flat.  If you cut well it should lay on there perfectly.  Hold it in place and trace around it with your sharpie(a fine point sharpie works best for this).  Cut it to the outside of the sharpie line using the same method as #1.  Fine tune with a flap disk and files.  In the end they should look like this:



Now all you have left to do is weld!  I prefer stitch welding.  You are going to have to increase your heat and wirespeed to get in that steep corner at the bottom of the U.  Remember, as gun distance increases, heat/penetration decreases.  I think i used about 65 wire speed 6.5 heat for the flat parts, going up to 75/7.5 for the inside corner.


And there ya go, one perfect merge for $25 and about an hour of work!

If you guys want any more tutorials like this, I'd be happy to do some.  I've built my whole car with not much beyond my milwaulkee grinder(well two milwaulkees, burnt up one halfway though ) and some thought.  Let me know what you want to see.  I'm thinking of doing a non-symmetrical merge next.

[ddv005]

You da man 

[Maliboost]

the food coloring trick is a great idea.

Bob

[Keith306]

wow great idea, i love cool little tricks like this

[mystang]

humm now if we could put our heads together to figure out how to get a pipe to merge into the bottom/side of a u bend

[TomServo]

Once I finish my exhaust in a couple weeks, if I have an extra bend I'd be happy to do another tutorial.  If you can find a pic on someone's setup of exactly what you mean that'd help.

[TrendSetter]

isntead of food coloring i always use a sharpie.  i keep black and silver on hand depending on the material i need to mark. it comes off clean with brake cleaner once youre done.

[chainfeed]

humm now if we could put our heads together to figure out how to get a pipe to merge into the bottom/side of a u bend

Yah this took awhile to do, be nice to have some kinda trick to make it go easier.

[Got N2O]

nice merges, and nice writeup!  Thanks!

[heytonyman]

Great little how-to! Very informative. We'd love to see some more tech tips!

Tony

[slowfox]

Good Idea man.               

[02Z28M6]

That's so Martha Stewart with the food coloring and all.
Awesome idea!

[Eliot]

Neat idea with the food colouring. What about doing it the other way round.. cover the pipe in either masking tape or perhaps just paper and put the food colouring in the water?

[TomServo]

Neat idea with the food colouring. What about doing it the other way round.. cover the pipe in either masking tape or perhaps just paper and put the food colouring in the water?

That should work as well.. the only thing is it wouldn't be as easy to re-do it if you mess up, since you won't be able to effectively 'wash off' the food coloring.  But if you're dealing with a surface that doesn't take well to this method, it might be an option.

[Kechup]

Good info!

[Jake]

 Neat idea! Its the simple things in life that make it worth living! Thanks

[65ShelbyClone]

Man, you need some Dykem machinist's blue, but then again that might count as "special" tools.

[turbostang]

Man, you need some Dykem machinist's blue, but then again that might count as "special" tools.

 That would defeat the purpouse of the food coloring. The food coloring rinses off with water and leaves the perfect line - the Dykem won't do that.

[65ShelbyClone]

Yeah, but Dykem comes off with acetone/brake cleaner which will degrease the part too. Just IMO. You abviously got the job done better than I would have. 

[TomServo]

I did have several options, paint/paint thinner, ink/thinner, etc.  But since you need a relatively large ammount of liquid(a few quarts), I didn't think it was logical to use up $3 or $4 worth of thinner to make one merge.  Food coloring is really cheap and so is water, so I'm only paying a few cents in materials.  And I don't have to worry about disposing of the stuff, just dump it on the ground.

[Jarhead]

thats awesome info to have, if you post up more tutorials, i will definately read them

[amish_terrorist]

awesome post    i am going to have to make something similiar for my 3800 build.  any tips for making the "merged" end fit a  rectangular t4 flange?

[TomServo]

Not really, all you need is a hammer and something flat, I usually use a piece of plate steel(~1/4") lyin on the concrete floor.  Ball peens work well for hammerforming merges like that, you can get into the corners with the ball part of the hammer to get a nice tight radius.

[BigNate]

Great info Tom!  Thanks!

[BlownShovel]

awesome post    i am going to have to make something similiar for my 3800 build.  any tips for making the "merged" end fit a  rectangular t4 flange?

The ball peen trick works...and if you can fit things I often sq pipes by using a bench vice and hammer..sometimes using misc pieces of stock to get the right shape...

Walt