Exaust tuning seems to be part magic. I recall reading Kaase picked up a bunch of bottom end torque by sleeving down the diameter of the collector on one of his 385 engines. Seems as over scavanging of the exaust at low rpms may be a common problem.

I've been following the header tests and subsequent discussion.  On my blown race car, I'm using Sanderersons like the circle track headers Ted tested.  1 5/8 tubes into 3" collectors.  No mufflers. I know the theory of header operation is scavenging at the exhaust ports.  But I have constant problems blowing the header gaskets.  What am I missing here???  For all intents and purposes, I shouldn't have pressure on the gaskets.

John - "The Hoosier Hurricane"

John: Possibly what you are seeing is the results of a very sharp reversion pulse from your exaust.

Obviously  what you have works well. Do you suffer any performance loss with the blown out gaskets?

I don't notice any difference in performance, it just makes it pop out the collectors when I let off, and it blackens the porcelain on the plugs.

John - "The Hoosier Hurricane"

John I don't have an answer but I remember back to my circle track days we were always having to change header gaskets. sometimes two times a night. We tried everthing we could think of including have the flanges surface ground. Have you tried a set of copper gaskets?

Glen Henderson



Freedom is not Free

Letohatchee, AL

Glen:

No, I haven't tried copper.  Actually it's no big deal, I only replace them when the headers are off for some other reason.  Have had the flanges ground flat, also have put a weld bead around the openings and had them ground flat but not ground to the flange, left themn sticking up a little.  The reversion thought may be what I'm dealing with, never considered it.

John - "The Hoosier Hurricane"

John.  Tubes too small and building up too much pressure at the header gasket?  On Randy’s blown dragster, 2” tubes were used specifically because his engine was supercharged.  My thought process says to use a much larger tube size on a blown application than would be used on a normally aspirated application.

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

Ted,

       I have seen formulae for the primary lengths, but never the "Collecter" lengths. We used hear that you cut the collecters at the "Blue" lines on the pipes, I always used ET's to determine where to stop. In many cases the added low or mid range torque got the car through quicker than just top end HP. I spent about three months getting a 67 Pontiac Sprint (OHC-6) right. Car would go 12's with 230 ci and break store windows two miles off. The big deal then was the square Box collecter, never could make that work.

    John's tubing diameters are too small for the HP he makes, BUT, it's an automatic and fairly heavy. So maybe the mid range torque actually helps out of the hole. He's TWO SECONDS quicker than my car, with a 6-8 mph advantage. Something works!

I don't understand the 45 degree thing unless it spreads the torque curve out.  

 Marv: I'd think the copper would be annealed by one or two passes. Exhaust gas Temps will exceed the melting point of aluminum, or 1100 degrees. More than enough to anneal copper.     

Frank/Rebop

Bristol, In ( by Elkhart)