Jim Hand of Boyles works has done extentsive testing on what mufflers actually work as far as performance goes, since many argue that flowmaster and similar mufflers flow rates are low but they work becuase they pulsate, he used actual track testing, and always had an open headered comparison as a constant.
He was looking for the best flowing quiet muffler, and found Dynomax (Walker) #17288 21" lenght mufflers to be very close to the best flowing mufflers he tried but very close to the quietest also.
He tried 2 types of flowmasters, supertrapp 18, Borla, cylone turbo, thrush, xlerator, and supertrapp 12.
Check it out: http://www.boyleworks.com/ta400/psp/exhaust.html
If best streetable ET is your concern then mufflers are not the only important thing in your exhaust, your header, collector, and piping are also very important.
Ed Bigley has uses Dynomax 1-3/4" headers on his 468" BBC chevelle, and with Header pipe your main concern should be practicality, large headers mean for the most part are harder time getting to the spark plugs! 1-5/8" tube would probably be best for your application.
As far as collectors go the best i've seen in action are Flowmaster 4-2-1 scavenger collectors, they improve torque throughout the band, and HP.
A crossover pipe is also important, Jim Hand has tried H and X both were an improvement over none, but the x-pipe was better for his application, When building exhuast do not forget that a crossover is important.
Tube size is also important, the larger the tube the more "potential" flow, this means the bigger the pipe the more exhaust you can put through it at the same rate. A smaller tube will improve midrange and low end torque over a bigger pipe, and in some cases (if chosen correctly) it wont effect top end.
If ET's and street/strip performance is not your main concern and what the car sounds like is, the just buy what you like as far as sound goes, and ignore the flow numbers.
Ed Bigley is using dynomax 1-3/4" headers, flowmaster scavenger collectors, a 3-1/2" X-pipe, 3" pipe, and Dynomax oval race magnum mufflers. I know 1st hand that this system works, sounds awsome (not excessivly loud, but has a nice sound) and flows plenty, enough for ED to move his 4000lb car 10.48 in the 1/4 with a 1.37 60ft off a foot brake.
Jim Hand uses Hooker 1.75" primaries, 3" collector; Dr. Gas 3" X Crossover into 3" Torque Technologies pipes followed by 3" x 2.5" Flowmaster reducers that enter 2.5" Walker # 17288 21" length Ultra Flow mufflers that are located behind the rear axle; exhaust exits Walker madrel 2.5" tailpipes. Headers modified to fit ports, cleaned up pipes into collectors, and 2" added to all left side primary pipes to more equally match right side length
His best ET that i know of (he might be doing better now, but hasnt updated his site) is [email protected]
115.2mph, with a 1.59 60' time. The car is a 4075lb (with driver) wagon, and he's using ET street tires and only a 3.55 gear! The engine is a 473ci pontiac.
I am not trying to use this as a controversy, this is for you guys to benifit from if you choose to, if not then i wasted my time. Benifit from it my friends
I copied this from one of my posts a few days ago, and no one responded after that.
My suggestion is Black dynomax 1-5/8" headers, remove collector install Flowmaster 4-2-1 scavenger collector, 2-1/2" X-pipe crossover, 2-1/2" pipe, Straightline performance "street" mufflers ($120 pair, less the flowmaster i think). Or dynomax oval race magnum.
Stock locations for mufflers are typically the best spot becuase the exhaust gasses cool off the farther away from the engine they get (downstreem) so a muffler is less of a restriction in the back of the car, then it would be if the exhaust was routed infront of the rear tire.