Did I buy the right headers size?
 

I have a stock Row 84 Carrera with a 3.2 that I'm upgrading the exhaust on. So the general consensus is that I needed 1 5/8 size headers for the 3.2. Recently I purchased a set of headers and Im not 100% sure if I bought the correct size. They do measure 1 5/8in on the outside diameter however inside diamter is 1 1/2in. Did I screw up or are these the correct ones for me? Thanks

Headers are tubing so they are measured by O.D. Yes, 1 5/8ths is a good size for the 3.2L engine.

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So to clarify, whenever a manufacturer states the size its always O.D. and never I.D. correct?

Tubing is normally specified as OD plus wall thickness. Like 1.75 x 0.90 for a common roll cage tubing size.

Yes, correct.

Did you mean to say ID plus wall thickness? because otherwise wouldnt the OD already account for the wall thicknes?

Let me rephrase my original question; Since my ID is 1.5" and OD 1 5/8" would they still be considered as "1 5/8in" headers thereby making it the correct headers for my 3.2?

I apologize if I sound thick headed

To be clear, tubing is specified by O.D. *and* wall thickness.

I have yet to see a header manufacturer specify wall thickness unless asked.

No, you don't. Just remember that headers are measure by the O.D. so your headers are 1 5/8ths.

Thank You @winders

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It is good to note wall thickness as different materials may use significantly different wall thickness. For example, our 321 stainless headers use 0.049" wall thickness due to the strength and heat tolerance of the material. Most 304 headers use 0.065" and some mild steel headers can go up to 0.125". This is a tremendous difference in ID, let alone weight. The exhaust port size on the 3.2L Carrera engine most closely matches the 38mm ID typical of 1-5/8" stainless headers, which is why 1.5" primary SSI and headers are considered too small for that application.