Your post made me go check mine (still in a box waiting to get the AIR tubes cut off)...

I purchased mine from "KOSpeed" which is DNA Motoring. The box and all paperwork (including invoice) say DNA Motoring. The reason I went with the KOSpeed listing is because it was $182 vs. $199 from DNA Motoring's eBay account. With that said, DNA Motoring is an actual parts company out of California: http://dnamotoring.com/store/

Anyway, I measured the inlet and it is indeed 1-3/4"; however, upon closer inspection, I noticed the primary tubes were flared out a bit before they were welded to the flanges. I then measured the primary diameters at various spots and found the primaries are 1-5/8".

I have reached out to the seller in hopes they'll take them back. While a great price, I'll spend just a bit more for those Speed Engineering ones that are truly a 1-3/4" primary rather than just inlet.

 

I was under the impression that header primary measurements were of the outside diameter, not the inside diameter. If this is the case then a 1 3/4 OD primary would naturally be smaller on the ID. I think that is the standard. Here is an excerpt from a Car Craft article, link below it if anyone is interested....

--------Here's an example of how this approach can work. Suppose you have a 350ci small-block (43.75 cubic inches per cylinder). A primary-pipe torque boost around 4,000 rpm is your target engine speed. The choices for pipe size are 15⁄8 inches, 13⁄4 inches, and 17⁄8 inches. If we assume a tubing wall thickness of 0.040 inch, each of these od dimensions requires subtracting 0.080 inch when computing cross-section areas.---------

http://www.carcraft.com/techarticles...s/viewall.html

The math is simple, using that 0.040 tube size a 1 3/4 header will have an ID of 1 5/8

 

^you're correct... but the O.D. of these primaries is 1-5/8". I will take pictures of the specs before I pack them back up to return them.

I also received a response from DNA/KOSpeed... very awesome customer service. They sent me a RMA and will be crediting me when they receive the headers.

 

I purchased mine from Speed Daddy on ebay a little over a year ago. Bolted right in with no problem and are still running great on the car! I would definitely go with them again if I had to.

http://www.ebay.com/itm/RACING-MANIFOLD-HEADER-EXHAUST-98-02-CHEVY-CAMARO-FIREBIRD-TRANS-AM-LS1-5-7L-V8-/190851351316?pt=Motors_Car_Truck_Parts_Accessories&fits=Model%3AFirebird&hash=item2c6fa08314&vxp=mtr

 

Got it, thanks for clearing that up. And yeah, would love to see some pics.

 

I feel bad that I indirectly made you return your headers but glad you'll be happier in the end. How much are the Speed Engineering ones?

 

Had great luck with OBX But hate Chinese copycats which is what they are

 

Don't feel bad! I'm glad it came up. I will actually start a new thread about the issue once I get the pictures with a set of calipers. I think everyone needs to know about this before buying their eBay headers. I'd really like to see everyone else who has installed them measure their primaries to see...

As for Speed Engineering, they're like $350 with a y-pipe.

 

Yes, or $229 for just the headers, so not much more than Ebays. liking this option more and more....

Hey Speed, out of curiosity, what do the inside of the collectors look like?

 

Here's the answer to all peoples' questions...

https://ls1tech.com/forums/generatio...l#post17455942

 

You know what I like to hear? The type of stuff I'm getting over here.

https://ls1tech.com/forums/generatio...primaries.html

People with relevant info. There are also several links to other threads that help out a lot too, PROVIDING RELEVANT info. Lots of posts by Speed Engineering mixed in helping out with even more RELEVANT INFO. I guess my typical downstate personality/attitude makes me want to know more about things before I spend money on them. You stay red up there man, derpa derpa, derpa. At least the water is clean upstate. Cant beat the camping either. Makes it a nice place to visit.

 

I use 6 or 7 different automotive forums regularly. The LS1tech crowd is a tough bunch. I have some Jeeps and you wouldn't believe the difference between the jeepforum and cherokeeforum guys compared to people on here. If I didn't love my Camaro to death and need to use the search function that hardly works I would never come here. I'm half afraid to make a post asking any questions on here because you get flamed and made fun of. I don't know if it's the type of personalities that own these cars or if it's due to a lack of moderation.

You can ask a simple question on here and get put down because you didn't do things they way that is the acceptable way, or didn't buy the acceptable brand. Everything here has to be uniform. You can only do the acceptable mods, you have to have 1,000 posts or you get put down for being new to the site. REALLY, NEW TO THE SITE? You end up with a 3 page thread and no answers. On the Jeep forums you can ask a question and have guys reply telling you they are "only" 4 hours away and can come right over and lend you a hand or bring you a tool.

I love my car but I hate using this forum unless I absolutely have to. It's almost a last resort for me at this point. Just wish guys would quit being such buttheads.

 

It only takes one bad apple to ruin the bunch right? Unfortunately there seems to be a decent number of them on here. That's a shame because most people are cool and want to be helpful. But yeah, one guy throws a comment in and then the thread goes of in some random direction, is pages long, is half hate and insults and ends up being useless. I agree with your comment on moderating as well. I think it should be stepped up a bit. My opinion.