this is an exhausting topic
just covering some of the basics of exhaust sytems
To start we all know that incresing pipe size increases power ... to a point , if your car
has single exhaust it is well worth investing in Dual exhuast , even a poor system can
increase milage by 20% or more
On a 273/ 318 a 2" dual exhaust is ideal for most street applications ,
340/360 use 2 1/4 "
Big blocks generally like 2.5 " what is overlooked is how much 1/4" increases the area
of the pipe 2" is 3.14 square inches
2 1/4 is 3.98 " "
2 1/2 is 4.91 " "
3" is is 7.07 " "
as you can see going from 2.5" to 3" increases the pipe size by over 40% this is very
important as will be discuss later
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Most are familiar with the H pipe this ties a dual exhaust together & was used from the
factory on most High Perf Big Block applications what this does is at higher rpm you will
make excessive pressure in the exhaust in pulses as the firing cylinders push the burnt
gases out & this allows the pressure to cross over to the other pipe instead of creating
a blockage that can be felt at the cylinder head & allowing the exhaust to be more efficient
these will increase power & milage even on the small 273 /318 engines
The newest idea is the X pipe , this crosses the left exhaust into the right tailpipe &
right into left thes have been proven to be more effecient than the H pipe & still allow
the blancing effect of the H pipe , they also make the exhaust quieter but remove the
disticntive right & left sound , the 2 tailpipes sound the same with a drone instead of
firing left right. I have made my own X pipes & find they fit far better then off the shelf
X pipes
When installing an X or H pipe be careful with the placement , it is better to have it
behind the tranny to allow removal when nessisary
There are 2 ways of bending pipe , most places have a bender but it crushes the pipe as
it is bent & forms ribs into the pipe as it is bent , all factory systems were bent this
way but both crushing & having ribs in the pipe restricts flow. The other way to bend pipe
is mandrel bending where a plug is used inside the pipe as it is bent to keep the pipe the
exact size & perfectly round , these will make more power .TTI has an awesome product
they are mandrel bent & fit perfectly
Stock manifolds are basically restrictive & are designed for production ease over power ,
except in some cases of the early max wedge cars where elaborate manifolds were cast, some
other manifold are far better than others & most can be ported to help power & still retain
the stock looks
For more power , you need headers . These are difficult to install can make spark plug
changes tough & often leak if they are poorly made , the advantage though is first smooth
mandrel bent tubing & Scavenging. Scavenging is the effect of the hot exhaust exiting in a
hurry & by using along primary tube the pulse of hot gas will leave a vacuum behind it
which will pull the next pulse of exhaust into the header , this effect is not a minor one,
this will also pull intake air into the cylinder & can increase cylinder filling to above
110% at higher RPM , most manifolds & shorty headers cannot do this as the individual runners
inside the manifolds are too short to be effective . Again TTI has an awesome product for
quality , fit & plug changes
Backpressure, this term is misunderstood , back pressure is real & affects the exhuast, a
poor flowing muffler will create a plug in the exhaust & that is backpressure as the engine
has to work to push exhaust through the muffler , most mufflers do not work the way you
would think looking at them , often the mufflers you can see right through are extremely
restrictive , while other with odd deflector plates inside kill off the pulses in the system
& increase flow it is worth buying Good mufflers, some will actually help scavenging even
with manifolds as the whole exhaust system will help pull exhaust away from the heads.
The other use for backpressure is "you need backpressure to make power " this is Not true
what is needed is Velocity this is where we get back to pipe size , Ofetn a smaller system
will make moire power than a larger system as the exhaust leaving is kept at very high
speed in a smaller pipe this is what creates the very important scavenging , if the pipe
size is increased the flow slows down & power is lost wether in the primary tube of a header
or the exhaust system behind the header or manifold & as seen above increasing a pipe by
40% will make a Huge difference in velocity & scavenging & with most cars being operated
90% of the time in the lower under 4000 rpm range it is better to err on the side of smaller
instead of bigger
