Because the starboard side of the engine
fires #4 and #8 in succession, there is a
cylinder (#6) separating the two. Dividing
this manifold into two different sections by
grouping #2 and #4 in the front half of the
manifold and #6 and #8 into the back half
of the manifold works relatively well in
isolating the #4 and #8 cylinders. On the
ports side of the engine we have a
problem: The #5 and #7 cylinders that fire
in succession are next to each other.
Dividing the port manifold into a front half
and a back half groups cylinders #1 and
#3 together (which is okay), but groups #5
and #7 together
(which is definitely not okay).
This is exactly what we are trying to
prevent! The correct way to build the port
side manifold is to isolate the exhaust
gases from cylinders #5 and #7 all the
wasy to the manifold exit.
Lowering Backpressure
Lowering back pressure in exhaust
manifold is a combination of isolating the
exhaust pulses as discussed in the
previous paragraph, and simply
making the exhaust system larger. Some
techniques for lowering backpressure
include: large passages in the exhaust
manifolds, a large exit hole out of the
manifold, and a large exhaust pipe and
large radius curves in the pipe wherever
the exhaust gases have to change
direction.”
aluminum mercruiser manifold kit
Email us
1-888-426 2841
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A GLM performance aftermarket exhaust manifold will deliver a performance
increase over a stock OEM exhaust manifold. It can do this in two ways: by
separating exhaust pulses and by lowering back pressure.
(see below)
Aluminum small block Mercruiser exhaust kit weighs 50lb total!
Separating Exhaust Pulses
All V8 engines have a firing order that fires
two cylinders within 90 degrees of each other
on the same bank of cylinders.
With a firing order of1-8-4-3-6-5-7-2, we have
#8 and #4 firing on the starboard side of the
engine within 90 degrees of crankshaft
rotation.On the port side, we have #5and #7
firing within 90 degrees of crankshaft rotation
of each other. Of course, this also means that
the exhaust gases for these cylinders
immediately discharge into exhaust manifold
one after the other. At this point, when the
two cylinders fill the manifold in immediate
succession, the exhaust manifold becomes
overwhelmed with exhaust gases, creating
excessive backpressure.
In fact, excessive backpressure, from an
overwhelmed exhaust system will not only
keep spent gases from leaving the cylinder
head exhaust port, but in certain ports,
exhaust gases from adjacent cylinders may
find their way back in.
The solution is to isolate each exhaust gas
pulse for as long as possible in the exhaust
manifold. There are aftermarket manifold
manufacturers that go to great lengths to
isolate each exhaust pulse the full length of
the manifold, and there are some that barely
address the problem at all. Choosing a high
performance manifold that isolates each
runner is the key to building horsepower with
the exhaust system.----->
Because the starboard side of the engine
fires #4 and #8 in succession, there is a
cylinder (#6) separating the two. Dividing
this manifold into two different sections by
grouping #2 and #4 in the front half of the
manifold and #6 and #8 into the back half
of the manifold works relatively well in
isolating the #4 and #8 cylinders. On the
ports side of the engine we have a
problem: The #5 and #7 cylinders that fire
in succession are next to each other.
Dividing the port manifold into a front half
and a back half groups cylinders #1 and
#3 together (which is okay), but groups #5
and #7 together
(which is definitely not okay).
This is exactly what we are trying to
prevent! The correct way to build the port
side manifold is to isolate the exhaust
gases from cylinders #5 and #7 all the
wasy to the manifold exit.
Lowering Backpressure
Lowering back pressure in exhaust
manifold is a combination of isolating the
exhaust pulses as discussed in the
previous paragraph, and simply
making the exhaust system larger. Some
techniques for lowering backpressure
include: large passages in the exhaust
manifolds, a large exit hole out of the
manifold, and a large exhaust pipe and
large radius curves in the pipe wherever
the exhaust gases have to change
direction.”
aluminum mercruiser manifold kit
How they work and why the increase in power!
If you can't find what your looking for please
call.                              1-888-426-2841   
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