Here are dyno results showing what happens to the power output when a particular set of headers are used with and without mufflers on the 322” dyno mule.  The headers in this test are the EMC headers with 1.75”/1.875” stepped tubes going into a 3½”/2½” combination collector.  These are essentially the same headers used on the 2010 Engine Masters Challenge entry with the exception of 3” merge collectors being inserted within each  collector since this particular test took place.  On the EMC headers, the mufflers are an integral part of the exhaust tuning and scoring ends up being significantly lower without the mufflers in place.

 

The engine used in this test is a +060 over 312 with the cast pistons 0.025” in the hole and the heads are unported G’s with a light mill.  The compression ratio is 9.2:1.  Camshaft is a Crower Monarch with 238° @ 0.050” duration, 0.420" lift before valve lash, and using 1.4:1 no name rockers.  The intake is the Edelbrock ‘573’ 3X2 using Stromberg 97’s.

 

 

Scoring is as follows:

With mufflers -      1667pts.

Without mufflers - 1650pts.

Lorena, Texas (South of Waco)

Here are some additional dyno results showing the differences again with and without the mufflers as well as another set of headers throwed into the fray.  The engine in this case is a 375” Y with nicely ported iron ‘113’ heads and 10.2:1cr.  Camshaft is 254°/258° @ 0.050” and 0.595”/0.602” intake & exhaust lifts respectively with 1.6:1 roller rockers.  Intake manifold is the Mummert dual plane with a 824cfm Holley carb.  The EMC headers are the same ones described in the above post.  The racing headers are 1.75” diameter ~31" long tube headers with 18” long 3” diameter collectors and are the ones used on my Y powered altered roadster with a 337” Y.

 

 

Scoring in this instance is as follows:

EMC headers with mufflers –  2129pts

EMC headers w/o mufflers –   2096pts

Racing headers w/o mufflers – 2114pts

Lorena, Texas (South of Waco)

Ted,as I would expect the mufflers really helped with the torque. Just wondering what type of muffler you used? Mike

1956 Fairlane Victoria (ORREO)

 

Overlooking Beautiful Rimrock AZ

So unless I am missreading the charts, you are getting more torque and horsepower with mufflers? So why, back in my street and strip racing days, did I do better with open exhaust than running through the mufflers?

It’s all in the combination but if the muffler itself is too restrictive, then topend performance is going to suffer regardless.  Magnaflow mufflers with 3½” inlets and outlets are being used and the mufflers essentially becomes an extension of the collectors without much in the way of a flow restriction while also exhibiting some good sound deadening qualities.  The EMC headers have header tubes that are larger than normal for a Y and collector tuning in this instance makes a lot of difference.  The larger tubes are needed for the topend horsepower numbers while the mufflers helps to restore some of the lowend by being a part of the collector tuning.  A longer collector can be made to do essentially the same thing as adding the mufflers so look at mufflers in this instance as being a part of the header and not necessarily just a sound deadening device.  Controlling the exhaust pressure waves in the collector area is key here and the mufflers become a part of that equation. 

 

Without the dyno, it would be difficult at best to quantify what works and doesn’t work in regards to some of the subtle changes being made on the exhaust system.  The general rule I adhere to is always err to the large side when dealing with exhaust systems and especially where wide open throttle performance is being optimized.  If an engine is running at a steady state 2200-2500 rpms day in and day out, then small tubes will be more efficient than large tubes.  The volume of air that must pass through the tubes at a light throttle opening is obviously much less that the volume that must pass under wide open throttle conditions.

 

Here’s an interesting tidbit regarding some past experiences with headers on my drag car.  The 427 HiRiser in my ’64 Fairlane doesn’t like mufflers at all.  Adding 4” inlet and outlet mufflers to the ends of the existing collectors kills performance on this car to the tune of  two tenths in the eighth mile.  That’s a bunch and especially considering that the mufflers are only 12” long and appear to be a wide open hole all the way through them.  But a little history on this particular exhaust system.  The headers started life out as 2.125” tubes going into 3½” diameter 6” long collectors.  I changed the collectors out to a 4” diameter collector the same length and the car still ran the same et’s but sixty foot times slowed while the mph picked up.  I then added 4” diameter 18” longer collectors to the existing collectors and picked up the missing 60’ times while not losing any of the gained mph.  Exhaust tuning is greatly improved at this point.  Adding mufflers to that conglomeration then kills what was gained on both ends of the track.  What hasn’t been tested on that combination is simply removing 12” of collector length and replacing it with the 12” long mufflers and seeing what the performance differences are.

Lorena, Texas (South of Waco)

I was, and still am, running stock Ford mufflers on my '57 Bird, without the resonators. Better mufflers and larger pipes are probably the answer. Recall reading about some realy fast cars running with mufflers. Better technology.

Slumlord:

When I was drag racing my F engined '57 Bird a couple years ago, I changed from the stock mufflers and 1 3/4" unresonated tail pipes to 2" in and out mufflers and 2 1/4 tail pipes and picked up a good 1/2 second in the 1/4 mile.  I didn't re-tune the carb or timing after the change, I probably could have helped it even more.

John - "The Hoosier Hurricane"

I've never tested really good headers on my F code, although a set of Jerry's small pipe "street rod" headers picked up 50 Ft lbs of torque on the Dyno at 3200!

   I run a 2 1/2" system with an "X" pipe and Flowmasters on the factory manifolds. The car runs the same ET's and speeds with this as it did with open pipes, or A set of Hedmanns and 2 1/2 collecters. I removed about 75 lbs with the Hedmanns by removing the manifolds and the entire exhaust system, yet the car gained nothing in et or mph.

Frank/Rebop

Bristol, In ( by Elkhart) 

Here’s another muffler versus no muffler dyno test using the EMC stepped tube headers.  Completely different engine combination this time as it’s a 314 incher.  Engine particulars include a 3.810” bore (+060 over 292 block), 312 crank with turned down mains, C2AE truck rods, ported ‘G’ heads, 12½:1 compression ratio with Dykes rings in the top lands, extrude honed Blue Thunder aluminum 4V intake, Isky 505-T cam with 254° @ 0.050” duration ground on 108° lobe centers and installed at 106° intake lobe centerline (2° advance), 1.6:1 Dove rockers, and a 830cfm Holley vacuum secondary carburetor sitting atop a 2” HiFlo spacer.

 

  

Scoring:

With mufflers – 1713.0 pts.

W/O mufflers – 1714.8 pts.

Lorena, Texas (South of Waco)

Would be interesting to see what happens by varying the collecter length with the mufflers installed. The torque curve looks like what happens with a longer collecter length (when you installed the muffler).

Frank/Rebop

Bristol, In ( by Elkhart)