[DeTomaso] 180 degree headers

[MikeLDrew at aol.com]

In a message dated 5/13/06 20:46:33, comeau2 at comcast.net writes:

<< What are some of the pluses and minuses of these headers?  Car is street 
use only.  351-C  steel heads.  purchase of header, mufflers, jet coat is going 
to cost me how much?  won't hold anyone to the exact amount just somewhat in 
a range am i looking at.  And what else am i over looking?   >>

>>>Here are the pluses:

1)  Bling.

2)  Some people like the exhaust sound, which is TOTALLY different from a 
normal V-8 sound.  Due to the matched exhaust pulses, the engine sounds much 
smaller, and rather European, like a Ferrari.  It literally screams at high rpm.

3)  Highly theoretical exhaust scavenging increases; this requires the 
exhaust system be perfectly designed, which most probably aren't.  If it is perfect, 
there are theoretical horsepower/torque advantages to be had.

Disadvantages:

1)  Cost.  These things cost a fortune, as they are very labor-intensive to 
build

2)  Complexity.  Installing them in the car is no picnic; some people have 
found it easier to partially remove the motor in order to install the exhaust.  
They also rarely fit properly when bought, and require a fair bit of 
heating/bending/percussion/profanity to get them to line up correctly.

3)  Servicing access:  Hope you put good spark plugs in, because that's the 
last time you'll ever be able to get to them easily!

4)  Exhaust leaks:  180 systems typically leak like crazy.  Because they are 
heavy and all the weight is above the header flange surface, they frequently 
break the header bolts/studs which then causes the flange-to-cylinder-head 
gaskets to blow out.  180 systems also frequently use a slip-together design for 
the various components which is notoriously difficult to seal, so it's common 
to find exhaust leaks all over the place between the flange and the tip of the 
mufflers, unless (like the factory system) the components are all solidly 
welded together.

5)  Don't ever plan on using your car as a CAR again--your trunk is now 
history.

6)  Remember that nice paint job you used to have on your decklid?  You can 
kiss that goodbye too unless you take serious precautions to insulate the 
underside of the decklid (kits are available to do this--more money, more weight)

7)  A/C?  What's that?  Most 180 systems are designed to exit out the center 
of the car, where the A/C used to live.  So you either get to be very, very 
hot, or spend big bucks (MORE money) relocating your A/C to the front (oh, and 
your radiator better be top-notch or your new A/C will cause your motor to 
overheat--MORE money)  FWIW the factory Gr4 race cars initially used 180 systems 
that exited through holes cut into the wheelwheels, and out the stock muffler 
locations; later versions went through the A/C grille.

8)  Power/torque benefits present in engineer-dork SAE papers, but not so 
much on engine/chassis dynos.  Last year Kirk Evans tested a single 351C with a 
half-dozen or more Pantera exhaust systems on a dyno, including a 180 system.  
The horsepower spread between the best-performing (which happened to be the 
180s) and the worst-performing system was only NINE horsepower!!!!  180 systems 
were in vogue for a brief period during the early and mid '60s, but by the 
late '60s, Can-Am and Trans-Am engineers had figured out that the advantages 
weren't worthwhile.  How many Can Am or Trans Am cars can you think of that used 
180 systems?  Zero.

9)  Sound.  Gone is the bad-ass rumpity-rump of a healthy V-8.  While the 180 
system sound will make your hair stand on end at 7000 rpm, at idle and down 
low (below, say, 3500-4000 or so), your typical 180-degree equipped Pantera 
sounds like an old VW Beetle with a shop rag stuck in the intake of one of its 
carburetors.  

Now, as to the cost:

Figure $2000-2500 for a 180 system; that includes the coating.  The smart bet 
is to buy the system uncoated, then bend/heat/malletize it as required to 
make it fit your car, THEN coat it.

Budget another couple of hundred bucks for heat shielding (don't forget to 
build a heat shield box for the carburetors if the exhaust pipes get anywhere 
near them, otherwise you'll boil the gas in the rear bowl)

If you plan to have A/C, plan on a couple of thousand bucks to move it to the 
front of the car, as most kits come complete with a new 
radiator/condensor/fan setup.

As you can probably tell, I'm no fan of 180 systems for street-driven 
Panteras.  I will admit that the sound can be intoxicating; I drove a Pantera 
equipped with Webers and 180s from Los Angeles to San Francisco, and on those rare 
occasions where I wound it out, it sounded great.  Most of the time it just 
sounded like a VW getting 7 miles per gallon. :<(

If I were building a race car, I would consider a 180 setup just because it's 
'right' for the car--and I would be revving the piss out of the thing all the 
time.  But for a street car?  No way....

Mike