3" exhaust systems

[william1]

 i need to update the exhaust on my 69z, i have been looking at the magnaflow 3" SS  systems with the X pipe, but the more i look around the more confused i get, 2".5 or 3", stock look or not, etc, originality is not the main thing for this one, just a nice solid performance good sounding system, any help on this would be appreciated..

[JohnZ]

A 3" exhaust system (with all its fit and clearance issues) may be great for "bling" on cruise night, but it's a waste of money; exhaust gases cool VERY rapidly before they ever get to the mufflers, and their density and velocity go WAY down in a hurry. A street engine doesn't need a 3" exhaust system.

[hydromo]

I have a ZZ427 crate engine headers built by Dan Lemons and a torque tech exhaust system 3 inch works great

[77thor]

3 inch pipes are only recommended for over 500 HP engines....

[hotrod68]

I know if you uncork a 302 with headers you'll pick up 3-4 tenths at the drag strip, and that's significant. It's a balance of cam, compression, and exhaust gas velocity v/s backpressure. I have a 3" system on my car with a 406 and wouldn't dream of choking that engine with 2-1/2" pipes. But with either size pipes, the most important thing is the pipes being mandrel-bent. A 3" system with conventional bends is no better than a mandrel-bent 2-1/2" system from my experience. My 2 cents and good luck!

[LB68SS350]

William -     I think a 2 1/2"  mandrel bent system on your Z would be the way to go. That's what I have on my '68 SS with a 355 (.030" over 350). It sounds great and makes really good power. I concur with JohnZ about losing exhaust velocity with a 3" system. That would KILL your torque, not to mention fitment problems. With the system I bought from Torque Tech, mandrel bent, 2 chamber Flowmasters, all 2 1/2", the car made 385 rear wheel horsepower and 448 rear wheel torque on the chassis dyno.     Larry

[william1]

went with the magnaflow 2 1/2" dual,,,  sounds great, the fit was no problem, and is solid,, will change a few things next time i have it off the floor, but over all, i'm happy with it, thanks for the info.......