I fabbed up dual pipes off my hooker longtubes (2210s) along the
T56 using the SPD trans crossmember. (Longtube T56 Swap CrossmemberSkulte Performance Designs)

The duals had cutouts on them and then Y'd back to a 3" single over
the axle and out thru a dynomax.

Exhaust is really quiet on the street, opens up nicely when pressed.

I took the car to they dyno yesterday, only picked up 5% through
the open dual dumps, versus the single 3" full exh thru the muffler.. A
dual exhaust with longer pipes won't even do this well.. This is with a
427 smallblock pushing 420 rwhp thru the muffler.

Everyone working so hard to put duels on 12+sec cars, might want to
rethink.. Just throw the LongTube xmem on and a Ypipe with a 3"
"standard" exh back, and don't lose any ground clearance..

YMMV

mike

 

An ideal exhaust will make nearly the same power corked as uncorked, one of the magazines did a dual setup a while back that had 1% loss over open headers and still made 93 db.

5% on 525 BHP is almost 30 horsepower. How can you say that is insignificant? I would say 1-2% corked would be a good number, if you can pull your exhaust off and pick up 3 tenths you aren't impressing anyone.

 

This is why he installed electric cut outs. Just a flip of a switch= open headers....Plus its gotta be quieter than duals that are dummped before the axle....

 

If you run at a track that has a db limit or you streetrace, open headers aren't going to be the ideal setup.

 

I agree....We have no db limit around here....I dont think 5% in street race is that big of a deal. Condition for traction are not ideal, so It might actually help...i think Mikes point is that alot of guys think they need duals when a good 3" exhaust will work for most application. It will be quiet and not draw unwanted attention. Plus the "seat of the pants dyno" will not be able to tell 5%

 

Exactly... And considering this is a big-inch small block pushing alot of air, I doubt
most street motors will even approach the 5%.. The 3" exh and dynomax have a
very nice street rumble, while giving up little performance.. The crossmember allows
the long tubes to flow straight back and not lose ground clearance, then tie into a
Y-pipe to complete the exhaust in 3".

 

Single 3" in/out muffler?

Do you have a Dynomax part#?

 

I used the Walker/Dynomax 3" over-axle pipe (43248) and
the single 3" in/out Ultraweld muffler (17220). Others have
used the stock sized 17233 and longer 17235 single in/out
versions also..

The ypipe is a flowmaster Y300400, and a hooker reducer
(11138HKR) and bits/pieces of 3" pipes/bends from the local
autoparts store..

and of course the SPD crossmember.

HTH
mike