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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Mike1973 on March 08, 2014, 07:49:27 am

Title: Facatory exhaust size
Post by: Mike1973 on March 08, 2014, 07:49:27 am: 1984 GMC 3/4 ton 2 WD 454 c.i.

What is the factory exhaust size, 2 1/4 or 2 1/2?
Title: Re: Facatory exhaust size
Post by: zieg85 on March 08, 2014, 09:57:43 am: Pretty sure it is 2.5 to the muffler and 2.25 tailpipe, at least that what mine appears on my 85 C20 with factory dual exhaust (original)
Title: Re: Facatory exhaust size
Post by: Mike1973 on March 08, 2014, 11:26:53 am: Think there would be any reason why I couldn't do 2.5 all the way back? I mean it's a stock 454, it's not like it requires some kind of precision or anything.
Title: Re: Facatory exhaust size
Post by: zieg85 on March 08, 2014, 12:50:41 pm: Quote from: Mike1973 on March 08, 2014, 11:26:53 am
Think there would be any reason why I couldn't do 2.5 all the way back? I mean it's a stock 454, it's not like it requires some kind of precision or anything.

I am going to do it when I get my 85 back on the road
Title: Re: Facatory exhaust size
Post by: Captkaos on March 08, 2014, 01:37:06 pm: No reason not to at all.
Title: Re: Facatory exhaust size
Post by: bake74 on March 09, 2014, 12:27:13 pm: You will not have any back pressure running 2.5" all the way back, it might help your truck run a little better, not much but some.