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.