Topic: K0-K6 Exhaust Flanges

[Ellz10]

Attached is a pic of the K0-K6 exhaust flange. I can't find anywhere that will sell me tube pipe with an ID of anything close to 1.57"

Am I just measuring incorrectly or what?

[HondaMan]

Tubing (pipe) is normally notated by the ID size.
The wall thickness varies for every different application for a given pipe (hi PSI, low PSI, sewer or supply lines, etc.), so you'll often find tubing in sizes like 1/2", 1", 3", etc., but the OD designates the 'schedule' of the pipe. When I was in the oilfield, a "2 inch pipe" for 20,000 PSI was 5.8" (minimum) on the OD while a 2" fluid feeder pipe was 2.25" OD.

For the exhaust it will also be in mm sizes.

The header pipes are also split at the ends so they will slip over the exhaust spigot. Most have 2 splits, some have had 4 (early K1), but those tended to crack and break off.

Are you planning on making your own pipes? Many car muffler shops carry the benders and piping, often in 18-8 stainless steel.

[Alan F.]

1.57" is equal to 39.878mm by the way.

https://www.everyexhaustpart.com/cart/tube/40mm-tube

1.5mm wall thickness equals 0.059"

Hope this helps.

[Tracksnblades1]

Look for 20 gauge 1.625 (304) stainless steel tubing. 1.625 - .070 = 1.555 ID.  20 gauge wall thickness is .035 nowdays..
You can adjust your ID by purchasing different gauges for example: 18 gauge 1.750 tubing 1.750 - .098 = 1.652 ID. (18 gauge wall thickness is .049 wall thickness.

Get close to your ID then have your muffler shop expand or reduce the end to fit your desired spigot.
If you’re using 304 or 316 SS tubing for mandrel bends, I’d purchase the most recently annealed tubing they have.
Your muffler guy will tell you why..😜

[Tracksnblades1]

Perhaps like this…

[Don R]

 Remember, the ID must be smaller than the OD. Otherwise, the hole will be on the outside. 

 Sorry, old pipefitter joke.
 

[Tracksnblades1]

Remember, the ID must be smaller than the OD. Otherwise, the hole will be on the outside. 

 Sorry, old pipefitter joke.

😜

👍

[Ellz10]

The header pipes are also split at the ends so they will slip over the exhaust spigot. Most have 2 splits, some have had 4 (early K1), but those tended to crack and break off.

Are you planning on making your own pipes? Many car muffler shops carry the benders and piping, often in 18-8 stainless steel.

So do I just cut one small slit on either side? How wide of a slit is nominal?

yes, seeing as I couldn't find anywhere in Michigan to make one. I hope my local muffler shop will lend their services.

Exhaust tubes are measured by OD, they are not “pipes” literally. Stock exhaust tubes are roughly 1.5” OD with a wall thickness of 0.063. That thickness is more than needed but common for mild steel tubes. Modern sport bike exhausts are typically closer to 0.039, thinner still if made from high grade stainless or Ti.

And for the record, tubing is measured by OD, pipes are measured by ID. The description of pipes/tubes is often interchanged but they are very different things.

And for exhausts, 304 stainless is the common standard, but 327 is a better grade. You won’t have much success fabricating your own stainless exhaust unless you have a high quality bandsaw to make the cuts. Fit-up is critical for proper welds, and to weld stainless you must back purge with argon else you will have oxidation that diminishes the durability of the weld and you WILL shorten the lifespan of the exhaust welds. Guaranteed.

Okay so exhaust "tubes" would be the correct terminology? Thanks! As far as cutting my pie cuts and any other cut, I don't have a proper bandsaw for such so I'm going to try and work with a buddy of mine who works at a weld shop here in town.to help me out, especially since I can't tig for crap.

Look for 20 gauge 1.625 (304) stainless steel tubing. 1.625 - .070 = 1.555 ID.  20 gauge wall thickness is .035 nowdays..
You can adjust your ID by purchasing different gauges for example: 18 gauge 1.750 tubing 1.750 - .098 = 1.652 ID. (18 gauge wall thickness is .049 wall thickness.

Get close to your ID then have your muffler shop expand or reduce the end to fit your desired spigot.
If you’re using 304 or 316 SS tubing for mandrel bends, I’d purchase the most recently annealed tubing they have.
Your muffler guy will tell you why..😜

This helped me understand everything. Thank you!!!

I'm not an idiot, but sometimes I get so flustered with something and I just can't understand what should be so apparent.

[Tracksnblades1]

^^^^

+1

Money or Time

Can be Money + Time…

If you’re doing the work, there’s bragging right on a job well done..
If you’re paying or doing it yourself follow 737 advice on the pie cuts. Pie cuts look way cool on three cylinder two strokes. Not sure about 4 strokes.

Any way look for some header mandrel bends not the kit. You don’t need the v8 flanges. Find your size and gauge and cut what you need out of the bends to keep welding down to the minimum. Follow 737 advice on the inside purge so your inside weld (100% penetration) looks as pretty (food grade) as your outside weld. I like 304 and 316 Stainless and haven’t experienced any cracking but I’m not using it with any epa engines either. Back before grey hair a big block in a short bed S10 required the path you’ve chosen. You’ll have a lot more room though. 😜

If you have a pipe fitter welder buddy they can make this look easy…

[Ellz10]

I hope you’re not planning on making your system from numerous pie cuts??? The amount of welding involved in that is astronomical. It takes about 36” of filler wire to wrap a 2.5” tube certain factors depending… it takes about 5’ to make that single weld plus all the cutting, fitting, tacking, purging, and other prep work.

Multiply that times the number of pies, plus the collector, tails, etc and you will be paying any competent shop well over $1,000 to make this system just in labor. Certainly if a friend does it for you, it will be much less expensive, but once he starts (unless he does Motorsport exhausts regularly) he will be cussing you up and down as soon as he realizes how much work is involved.

You would be far better off buying a quality 4:1 system and then cutting it apart and fabricating from the collector back.This will allow you to rotate the tubes from the exhaust ports in any alignment you desire 4:4, 4:2, 4:1 and save you enormous amounts of time and money.

A stainless pie cut exhaust won’t look like a Ti system either (if that aesthetic is something you are trying to emulate). Best technique is to autogenously weld the pie cuts (requires precise fit-up with zero gaps) while purging. That can be very beautiful but still takes all the time just no filler wire.

Just so you know the length of the tiger’s tail you’re pulling on…

No, I wasn't planning on making it from pie cuts. Even I know how ludicrous that is - so much work too.

I had budgeted $800-$1200 for the exhaust to be built, start to finish, but you're saying around $1k just in labor, yikes!!

I actually think that might be a better option for me - buying an aftermarket and then orienting them to my satisfaction! The only issue I would have with that is finding an aftermarket exhaust made in stainless steel. Any suggestions? 4-1 would be best I think.

Edit***  I looked and the only one I seem to be able to find is the Delkevic 4-1 stainless steel. Not sure how good they are.

I do need to take special care when making this exhaust due to the wet sump conversion extending the engine depth - ergo I can't route the exhaust directly under the engine.

I honestly hadn't even thought of doing it in titanium - I always thought stainless was just so aesthetically pleasing. Also, I'm guessing ss would be cheaper than titanium in every way.