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)

Frank.  You’re absolutely right in that the mufflers in the various tests using the EMC headers are essentially collector extensions from a design point of view.  I’ll add that on the drag cars I’ll use a 45° cut on the collector outlets which has always proven to be a benefit.  On the EMC engine itself, I was using ~8' of additional 3½" tubing behind each muffler as part of the tuneup on that engine.  Torque curve saw a drastic shift when the extra pipe was added.  When the extensive exhaust test on the +060 312 dyno mule is performed, I’ll include a variety of 3½” diameter extensions on the EMC headers just for the additional information it will generate.  A general statement on exhaust testing performed thus far is that each engine combination requires a different setup on the exhaust to insure optimum engine performance.  The testing on the dyno mule will give some generic guidelines but as is already evident in using the EMC headers on several different engines, the torque bands vary depending upon the total engine combination.

 

Here’s the pic of the EMC headers and mufflers that are being used.

EMC Headers – 1¾ X 1 7/8” stepped tubes with 3” merge collectors installed within the 3½” collector shells.  The Magnaflow mufflers are 3½” I.D. and add 18”  to the current collector length.

Lorena, Texas (South of Waco)

This fellow sells copper yblock exhaust manifold gaskets on ebay. The set I bought are very well made. I got them for to use when the aluminum heads arrive as I feel with the two different types of metals having two different rates of expansion a gasket will be required or the head/manifold area  will show wear/gouging. I have not decided if they should be annealed or not. My experinces working on diesel engines using copper gaskets say to anneal. Opinions?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=270630324210&viewitem=

marv

Copper exhaust gaskets definitely need to be soft to help them seal.  The copper header gaskets I use for the Y’s on the dyno are not annealed and do leak as a result of being essentially too hard.  They are not deforming as needed to match the header flange.  As a general rule, I have problems with copper header gaskets sealing on all engines when being used dry or without additional sealer (hi temp RTV) on them.  On the dyno, I can live with some minor header leaks but on a driver, these would be unacceptable.

Lorena, Texas (South of Waco)

Thanks Ted:



That is what I will do... anneal them before installation.

That way they will be soft and fit any imperfection on the mating surfaces. If I remember correctly it takes 700-900 deg F to get copper cherry red to anneal. Installing then driving would probably get the metals this hot just may take several re-tightenings. Annealing would do the job in one pass.



marv