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Old 10-29-2017, 01:37 PM   #6
Leonard60
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Join Date: Jun 2016
Location: Leslieville alberta
Posts: 374
Re: Exhaust diameter for a 71 stock GMC

Quote:
Originally Posted by 57rookie View Post
So I figured it out. I re measured using piece of tape and it is actually 7.75" in circumference. Then you calculate and it came out to 2.468" diameter so my factory exhaust at the inlet of the single muffler is 2.5". I knew it looked larger than 2". The tail pipe is 2".
Pipe is measured by nominal inside dimension. So 2" pipe would be larger that 2" on the outside. The inside of your pipe is likely what you call 2".
If you don't have a vernier caliper you can use 2 squares to measure the out side of your pipe then use the formula Pi X d and that will give you the out side diameter. This measurement only gives yo outside diameter not the tru pipe size.
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