The Pantera Place
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ANSA Muffler Modification

By Mike Dailey 

 

When I found my Pantera in 1998 it was equipped with Hall headers and a stock ANSA exhaust system.  The mufflers had gutted themselves from years of corrosion working away on the internal baffles and the internal perforated pipes. Some of the corrosion had worked its way through the outer shell and had been patched with some type of filler.  The mufflers looked ratty but had a pretty nice sound.  

As part of my early repair and replacement project I decided to buy a brand new ANSA system from Pantera Performance for $775 in late 1998.  The new system looked great, but after I installed it I immediately noticed that it was very quiet compared to the old system.  I missed the original sound, but I thought over time they would eventually get louder, but that never happened.

Being a typical Pantera owner that can’t leave well enough alone, I recently started thinking about how I could help nature along a little bit and make the mufflers more free flowing and louder.  Dave Bell has a web page that shows how he cut his GTS ANSA mufflers open and gutted them. I thought Dave’s idea was good but I didn’t want to cut open my mufflers.  The standard ANSA mufflers have a smaller inlet pipe than the GTS mufflers and adding to their flow restriction are discs that are spot welded into the front of the exit pipes. These discs close off the front end of the exit pipes and force the exhaust through small holes drilled in the pipes. 

 

View of Dave Bell’s GTS ANSA muffler cut open showing the internal perforated pipes, baffles and location of the discs on the standard mufflers.  The discs can be seen buy looking down the fluted exit pipes with a small flash light. The standard ANSA mufflers have the area between the two baffles packed with a sound deading material that looks like fiberglass. 

 

View of the exhaust flow route through the stock ANSA muffler.  The flow is in through the inlet pipe to the back of the muffler case, then through the holes in the exit pipes and out the fluted tail pipes.  Not a very free flowing system!  

I wanted to find a way to increase the flow without cutting open the mufflers so decided to focus on how I could increase the flow to the exit pipes.  Some people have knocked out the exit pipe discs by ramming a pipe down the tail pipe or sometimes the spot welds rust apart and they fall inside the muffler.  But that solution causes the loose disc to rattle around inside the muffler or you must cut open the muffler to remove the disc. 

My solution was to buy a 3/8” drill bit that is 12” long to drill holes in the disc from the back of the fluted pipes.   The drill bit was purchased from Lowe's. 

I was a little concerned that the 3/8” holes could cause a whistling or chirping sound but that was not the case.  I started by drilling one hole in each disc to find out how it sounded.  As I drilled more holes I could tell that the sound level was louder.  I ended up drilling five holes in each disc being careful not to drill through the side of the exit pipe or the spot welds holding the discs.  That's ten holes per muffler.  Unfortunately it is too dark inside the muffler to take a picture of the holes I drilled.   

The idea is to drill holes in a pattern like this but it is hard to control the hole positions with the long drill bit.  

From my calculations the ten 3/8” holes in each muffler increases the open area by 1.044 or about 46% of the inlet pipe area .  That area along with the existing perforations in the exit pipes opens it up quite a bit.  The exhaust tone is louder, but not too much and I expect the holes help reduce some exhaust back pressure.   

March 18, 2007 - Update

Being a typical Pantera owner I can never stop tinkering.  After I drilled the holes in the disc, I could see that the muffler had a couple of small vent holes in the back baffle and I could see the deading material behind the baffle.  I got a longer 3/8 drill and drilled five holes in the back baffle.  The deading material turned out to be steel wool and I was able to remove it by drilling holes in it and pulling it out with piece of coat hanger with a hook on it.  

    

After removing the deading material I was then able to drill a few holes in the front baffle so that the exhaust flow now works like this:

When drilling the holes in the front baffle, make sure that the angle of the drill will place the hole in the baffle and not in the bottom of the muffler.  It worked fine for me but I can see that depending how the holes are drilled it would be possible to miss the baffle.  The inside of my muffler now looks like Swiss cheese and is a lot louder. 

Removing the steel wool and adding the extra holes in the baffles made the exhaust a lot louder outside the car and also inside.  The famous Pantera 1900 to 2300 RPM harmonic resonance is way louder so do not make this mod if you do not like the sound.  I've always thought that the harmonic resonance could only be heard inside the car but after extensive testing in our local underground Wal-Mart parking area I discovered that it is loud outside the car too.  My car has always be good at setting off car alarms but now it does an excellent job!