[DeTomaso] Collector, Pipe, and Muffler Choices

[Daniel C Jones]

> Based on this, are we better off with a 2 1/2 collector and pipe
> into a 3 inch muffer, than three inches all the way?

For your application, probably the former.  The smaller diameter
collector is sufficient for your primary diameter and HP and allows
for larger radius bends.  The muffler is potentially the the big
restriction.  The style of muffler and well as the flow rate are
important.  A (properly sized) straight through muffler appears as
a collector extension while a chambered muffler like a Flowmaster
appears as a wave termination.  The OEM ANSA mufflers appear as
potato stuffed in the tailpipe.

> Didn't someone do a dyno tests on different headers years back?
> (probable Dan?) With about only 7hp difference?

You may be thinking of testing Kirk Evans conducted.  I've not seen
the results of that testing but Larry mentioned his Hall 180's did
best in that comparison.  I'd have to see all the particulars from that
test before drawing any conclusions.   Muffler type and sizing can
have a significant impact on the results of header testing, for
instance.  Also, a small difference in peak HP can still have a very
large difference in area under the curve.  In my own testing of large
tube (2 1/8" primary diameter), large collector (4" diameter), Econo
Altered headers versus Hooker street headers (1 3/4" primary, 3" collector
diameter), the peak difference was 1 HP but from 3500 to 4500 RPM,
the big tubes were down 20 ft-lbs.

> D. Vizard seems to think that shorty-headers (like our GTS's) and
long-tube
> headers (with collectors) tend to produce within about 5% of the same
> power, so maybe its not gonna make much real-world difference except
visually.

Vizard's testing on a street 350 SBC, showed small HP differences in primary
lengths of between 24 and 38 inches.  However, at 18 inches there was a
significant loss across the RPM range.  Note these headers had real
collectors,
not the shorty style of most Pantera headers.  In Vizard's testing,
collector
length was much more critical.  Also, collectors with too large a diameter
lost much more than collectors with too small a diameter.  In testing for
the
Engine Masters, both Kaase and McLain found a 3" diameter collector to be
optimal for their engines which produced peak power in the 650 to 700 HP
range.

I see overly large collectors on many Pantera 180 degree headers.  Unlike
4-into-1 headers, 180 degree headers space the primary pulses evenly in the
collectors so work better with smaller diameter collectors than the 4-into-1

headers.

> I received what I believe to be a Hall System with a car I'm presently
> putting back together.

My white Pantera came with the Hall "big bore" system.  If I were keeping 4V

heads, I'd cut the 1 3/4" diameter primaries half way down the length and
graft
on 1 7/8" tubes to get a stepped primary and then add a merge collector.
Also, in our dyno testing, the 4V heads responded to the Stinger exhaust
port
stuffers.

> I have Magnaflows on mine.

What part number mufflers do you have?  The online Magnaflow muffler catalog

lists the mufflers core size.  Looking at the single inlet, dual outlet,
5" x 8" oval case universal mufflers that have a 14" long body, there are
a couple options in both 2 1/2" and 3" inlet diameters:

 P/N 12158 (satin stainless steel) or P/N 14218 (polished stainless steel)
 Inlet/Outlet Size: 2.5in./2.5in.
 Core Size: 2.5in.
 Body Length: 14in.
 Body Shape: 5in.x8in. Oval

 P/N 12198 (satin stainless steel) or P/N 14221 (polished stainless steel)
 Inlet/Outlet Size: 3in./2.5in.
 Core Size: 3in.
 Body Length: 14in.
 Body Shape: 5in.x8in. Oval

Various style tips can be added.  Interestingly, some of the dual outlet
mufflers are listed as having dual cores but those are longer mufflers
which wouldn't be a good fit in the Pantera.

> here's a muffler that is similar...Magnaflow 13288. Pretty similar to
> the muffler you have noted but this one has 3" inlet with dual 2.5"
> outlet.  It's a little wider at 9" and only 4" thick...same length

Be aware those are the baffled (not a straight through design) XL series
mufflers:

 P/N 13148
 Inlet/Outlet Size: 2.25in./2in.
 Body Shape: 4in.x9in. Oval
 Core Size: Single 2.5in./Dual 2.5in.
 Body Length: 14in.

 P/N 13278
 Inlet/Outlet Size: 3in./2.25in.
 Body Shape: 4in.x9in. Oval
 Core Size: Single 3in./Dual 2.5in.
 Body Length: 14in.

 P/N 13288
 Inlet/Outlet Size: 3in./2.5in.
 Body Shape: 4in.x9in. Oval
 Core Size: Single 3in./Dual 2.5in.
 Body Length: 14in.

They should be quieter than the standard Magnaflows but may not behave the
same
way (i.e. won't appear as a collector extension to the header).

On the muffler construction, cheap mufflers like the OBX have only
fiberglass
packing.  While they may be acceptably quiet at first, over time, the
fiberglass
will burn away and they will get much louder.  Better mufflers like the
Magnaflows will have stainless steel wool as the sound deadening material
and, in some applications, there will be an added outer layer of fiberglass
for additional sound deadening.

Dan Jones