Why Not to Put Exhaust Headers on Your Car


rev up your engines, today I’m going to
talk about why not to put exhaust headers on your car’s engine,
now exhaust headers serve one purpose they allow the gas that has burned
inside your engine to come out the exhaust and then flow through the
catalytic converter through the muffler and out the back and on the factory cars
they’re called exhaust manifold, not header, cuz cast-iron can take a lot of
heat it’s strong it’s not gonna break, plus they’re relatively easy and cheap
to manufacture the exhaust manifold is under this heat shield it keeps the heat
from getting in and damaging anything under the hood and the design of the pipes
are for one main thing to get the exhaust gas to leave as fast as possible,
so the engine can have as most power as it possibly can and to run the most
efficiently, now when I was a young mechanic all vehicles were carburetored
practically and if you wanted more power out of a car, you could change the stock
to fancy headers like the ones in the picture behind me and a fancy headers
would flow better they had better heat characteristics,
they could be custom-made for each engine to get more horsepower, and since
they were simple, carburetored engines all you had to do was re-jet the carburetors,
put jets that were the right size so the air fuel mixture would remain perfect
since you changed how the exhaust flows you have to change how the air intake
comes in to put fuel into the engine, now back then if you had a stock Chevy 350
v8 engine and you put racing headers on them that were tuned correctly, you could
get maybe about 16 more horsepower out of that big v8 engine, but you have to
realize that most of that horsepower gain was at the really high rpms their
made more for racing than street driving since the headers aren’t made out of
cast iron, a lot of times they were stainless steel, cast iron is thick
stainless steel is thin, so they can have wider openings for the exhaust gas
the cast iron would be restricted down because it’s thick where the stainless
steel could be wide open and they’d flow better,
so headers in and of themselves don’t give your engine extra horsepower, they
just allow your engine to get the most horsepower out of its design that it
possibly can, while all modern cars are all fuel injected
and if you put headers on them you have to do a lot of reprogramming, you have to
find a mechanic with a five gas analyzer and a dynamometer and is able to
reprogram the computer to make it run correctly for the new flow that it has,
and in the case of many modern cars if you’re driving them on the Street in the United
States the exhaust manifold has the catalytic converter built-in, so if you
remove the stock and put on these racing headers you’re eliminating a catalytic
converter, you’re breaking the law you can’t take a Catalytic converter off a
car, so putting fancy headers on a modern car that you’re driving on the street
it’s just not a very smart idea now I know people are gonna say, Scotty oh the
guys that are modding their cars they put headers on, but yes that’s generally the
last thing they do when they totally modify a car to either race or to get a
ton of horsepower out of it and often in places where they don’t even do state
emissions testing, so they don’t have to worry about having it passed an emission
test every year to be on the road, first they’ll rebuilt the entire engine to
make it stronger, then they’ll put either a turbocharger or supercharger on it,
then on top of that as the finale they’ll stick nice fancy headers on the
engine so it flows as well as it possibly can and it has the most power
that it possibly can, now I still see guys trying to do it on street vehicles
here in Houston and then you see them going down the street and they’re shifting
gears you can hear the engine backfiring and popping through the exhaust, it’s
cause they just bolted headers on they didn’t change anything else and the car
doesn’t run right it can actually cause the Pistons to hole from pre-ignition
because they won’t run right, and sure they look cool when they’re under the
hood, a lot of times they’ll have them all polished and shiny and some of the
guys will wrap the headers with heat tape so they retain the heat better and
then they flow out faster for more power and they’ll remove the catalytic converter
sometimes even the muffler and have a totally free-flowing exhaust, they like
that giant loud sound, which is fine on a racetrack but in most places it’s highly
illegal they put out too much noise the decibel level is too high there’s laws
for that most states, so they won’t pass inspection because they’re too noisy and
since the stock exhaust manifolds have heat shields on them and the fancy ones
don’t, you stick headers on modern engine you can make the engine
compartment get way too hot, it’ll mess with the electronics and all the
wiring of a modern car and since you generally driving on the
street, these modern engine designs their stock are designed for generally
stop-and-go city traffic where they do most of their driving, not going top-end
a 130-140 miles an hour, so putting headers on any modern engine
it’s a dumb thing to do for something you’re driving every day on the street,
so now you know why it’s a dumb idea to put fancy headers on a modern car that
you’re gonna drive every day, sure it’s certainly fine if you’re building a race
car, for driving on the street that’s just stupid these days, because you’re
not gonna gain that much horsepower for the relatively large amount of money
you’re gonna spend putting the headers on and then having the system reprogram
to accept them correctly, so if you never want to miss another one of my new car
repair videos, remember to ring that Bell!