[wakesupremo]

Can someone please post pics of underside of a '69 firebird convertible with a 3" exhaust system. I would like to make one so that I don't lose power at the track but don't need to keep removing and refitting for the road.
Its a very limited space under there for 3". I only intend to go to the back axle with a straight / slash cut pipe, not over the axle.

[RocktimusPryme]

I cant help you on the pictures with a convertible, but what I would say is prioritize at least 15-20" as straight as possible out of the headers with no downsize in pipe. I would also say to use cutout at the back of that to really prioritize power, but it sounds like you don't want that.

But most of your huge power losses with exhaust come from things that occur closer to the header itself. If you have to have a design choice that may kill power, it kills less and less the further you get from the headers.

So prioritize that first 20 inches, then if you have to step down in tube size or just make some less than ideal bends it wont hurt as bad on the track times.

[JLMounce]

Suggest you pick up one of these. https://www.bmrsuspension.com/?page=...&productid=227

It's unlikely you'll get 3" pipes through the factory convertible brace. This piece is not only more rigid than the factory piece, but provides room for 3" exhaust systems.

[turbo69bird]

I hd 3 inch on My convertible years ago and I had to put spacers on the. X brace for the convertible to make it happen.
If I was to build one today for a street car I’d use V band clamps so could easily remove sections you’ll have the exhaust for a long time spend the extra money . Amortized over the life of the system it’s Pennie’s