For what it's worth, my '72 SS454 used 2-1/2" exhaust. Key point is that the big block tailpipe end runs parallel to the ground and terminates under the rear bumper with the expectation of a chrome exhaust tip being attached. The small block exhaust typically does a 45 degree downturn at the rear bumper with no chrome tip. Don't get the angled tailpipe if you plan to use chrome exhaust tips.
I haven't used stainless steel, so I can't comment. Hope this helps. TK
Thanks for the reply, I am going to use the factory SS tips (I have an NOS set), I'm concerned if the stainless steel will be too hard to modify if it should be the wrong size to accomodate the tips-I was thinking 2 1/2" was it I'm still hoping for a little affirmation though from some others!
The 'correct' size (as it pertains to oem) exhaust is 2.5" headpipes and 2.25" tailpipes. It would be helpful to know why you are concerned with the 'correct' size (originality or performance). If you're talking about a concours, why go stainless? There's no downside to stainless - most consider it an upgrade. Are you buying someone's kit, ie. Borla, etc.? It'll probably have 2.5" tailpipes. Or, have you found someone to mandrel bend the stainless pipe? Either way, should be the last system that car ever needs.
I have a set of the NOS tips and the 2.5" pipe of my flowmaster system fits perfectly inside of them. Does anyone know how far the flat area on the top of the exhaust tip is supposed to be below the bottom of the valence panel?? The way mine sits right now, they look a little low, and before I weld them on I was thinking of bending the tailpipes uppward a bit.
Alan, I'm doing this for a frame off restoration-maybe not a 'concourse' restoration, but a resto that I can drive and will look good and last over the years. So the stainless is for longevity and quality, not so much as performance. But I do still want the NOS tips to fit; also another question posted was a good one where and how do you line up the tips? What are the markers to find the correct are?
The correct dimention for the extension is 7/8" down from the bottom of the valance panel, and they extend out 2 7/16" measured at the center of the tip to the bottom edge of the valance panel, measured parallel to the edges of the extension.
Aren't the '70 Chevelle SS's supposed to utilize resonators ahead of the exhaust tips? That is an item usually missed. Since you're looking for the stock appearance you should consider it.
BTW, please comment, anyone who knows for sure on the resonators.
Go to the Gardner web site and you can hear sounds from different exhaust systems they manufactered. I purchased a set of rear tailpipe hangers for my 70 and they looked great. They are good people to deal with and the contact person their is Eric Garner.
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