Hey y'all,
I'm looking to get a new header made. I'm going to run it in the same location as stock. The main reason for going at this is I want to open up the ID for better exhaust flow. The stock inner pipe is 1.5 inch if I'm not mistaken? I know that really the max ID anyone wants to go on these savages is 1 5/8 inch or 1.625 inches. The main question is if I get a 2 inch OD tube with a 1.625 ID that will put the tubing wall thickness at about 4.75mm or .188 inch. When is wall thickness too thick for an exhaust? For one, I can guess that that dimension of steel tube will probably be heavier than the stock header and harder to bend. I want to go this route because I had just purchased a straight thru muffler that is 2 inch ID. I cut off the old mounting point for a muffler and ran it on the outer tube of the stock exhaust. It looks great and sounds great but now I want my whole exhaust system to perform great.
Does anybody have info to share? Has anybody gotten a new pipe made and what dimensions did you go with? What was the outcome?
I do plan on doing hi-comp piston, cam from lancer, and carb upgrades as well. I'm just trying to gather as much info as possible so I can knock it all out at once. The exhaust is the last piece to the puzzle... for the engine anyway.

What exactly does a thicker wall affect? I've read a few articles on the inter web that most exhaust tubing is between .030 and .060, but what if you went thicker? I haven't found any info that explains an answer. The only thing I can think of is that the exhaust won't be able to dissipate heat as quickly or effectively. But then again, most people wrap their headers with heat wrap so does it really matter that much about heat dissipation? I'll keep looking around. I think if I went with the dimensions I mentioned above the header will be way to heavy without additional support and I aint really about heavier. After all, bobbing means shedding weight, not adding it back on!

I just got done reading DragBikeMike's 97mm build and he used a Mac header which is 1.73" ID and OD is 2" I believe. That would put the Mac header wall thickness at around .140. No exhaust wrap though.

Thanks Fast650. I was trying to go 2" OD just for the fact of keeping my reverse cone muffler I just bought a few months ago, but to get an appropriate ID with 2" tubing will put the header at way more weight than I want. I wish I would have done more research before buying muffler. Knowing what I know now, I would have just bought the 1.75" version. Oh well, I'll just have to bite the bullet and buy the 1.75 version. Anyone want to buy a slightly used 2" reverse cone muffler? I'm going to go with 1.75" OD with the ID of 1.625. From what I'm reading, and from what you said, that seems appropriate for our bikes with a stage 3 cam and vm38 carb.

All you need are 2 strips of material .060"  thick rolled to fit.
And slip them in between the header and muff.