14 January 1999
The Restoring and Fixing Up For Performance of a 1973 Chevrolet Chevelle
Fixing up a 1973 Chevelle for performance and restoring it to original condition. When
building a car there are several different ways to setup a performance car and everyone has their
opinion. This 1973 Chevelle was setup for midrange performance. Every little thing makes a
difference. Someone should want something that is not too powerful and that can be driven
everyday that also looks good inside and out. The major mechanical parts that affect the
performance of the car are the engine, transmission and rear end. These parts should really be
rebuilt when restoring the car and sometimes bodywork maybe needed. Rebuilding a car is a
good idea for several reasons such as learning about the car, less maintenance, made for what is
wanted out of it, better performance, and a lot more reasons.
The Chevelle was introduced in 1964. The Chevelle is a mid-sized passenger car.
There were 3.7 million Chevelles manufactured from 1964 to 1972 (The Chevelle List 15). The
last so-called classic design of the Chevelle was in 1973. The length of production on Chevelle
tells that there were a lot of sales. The major changes over the years are the body styles and
trims like rear side window, bumper, headlights, tail lights and grill. The main mechanical
design has stayed similar over the years and is very similar to the Monte Carlo and El Camino.
Since the mechanical design has stayed the same over the years helps cheapen the maintenance
and parts access (Chevrolet Chevelle Automotive Repair Manual 2).
The engine is the part that generates the power to move the car. Torque is a measure of
power or tightness. Camshaft is a part inside the engine that opens and closes the valves at a
certain time. Cylinder heads hold the valves and cover the top of the pistons. Headers are a
tuned exhaust that connects to the cylinder heads. Intake manifold is the part on top of the
engine that distributes the fuel and air to the cylinders. Carburetor is the part that mixes fuel and
air and controls the speed of the engine. Piston is a part that moves up and down in the cylinders
and is located under the cylinder heads. The crankshaft is the part inside the engine that takes
the power of the pistons and moves 360 degrees transferring the power to the flywheel. The
flywheel is a part on the back of the motor that helps for balancing, starting the motor and
connecting the motor to transmission. The connecting rods are connected to the piston and
transfer the power from the piston to the crankshaft. Roller rockers transfer the power from the
camshaft to the valves thus opening the valves. Nitrous oxide system (NOS) is a part that adds
one more molecule of oxygen to the carburetor which helps for better combustion in the
cylinders. The transmission is the part between the engine and rear end that takes the power
generated by the engine and shifts at a certain time. The torque converter is a part of automatic
transmissions and lets the engine turns a lot and the transmission receives less tell a certain RPM
(Revolutions per minute) and the locks up. The rear end is behind the transmission transfers the
power ninety degrees to the wheels. Rear end gears is the part that transfers the power ninety
degrees. Differential is the part that connects to the gears in the rear end and transfers the power
to the wheels. Wheel hop means when the wheels bounce or hop.
Sand the outside of the engine. Make it smooth and contour the edges. This will make
the engine look a lot better. Porting the engine matches the intake manifold to cylinder heads,
which makes it nice and even without any overlap allowing unrestricted flow. Balancing the
engine makes everything on the engine nice and even weight wise causing a smooth even
rotation. Polishing the engine makes sure everything is nice and smooth so there is no resistance
for the flow of fuel, air and oil. Relieving (like contouring) the engine takes all the sharp edges
out and helps reduce wear. Putting 4 bolt mains on will allow the engine to take more
horsepower and RPM. Line boring the engine will make the new 4 bolt-main bearing caps nice
and straight on the engine. Taping the bolt holes will help clean them out and taking all the
defects out, thus giving the right torque when tightening the bolt. Deck and milling the head(s)
or engine block means that it is made nice and flat thus giving a better seal. Plastic-gage is a
nice helper in fitting the main bearing caps to crankshaft clearance (McGean 40-51). Honing
the cylinders with a hone will make the cylinder holes smoother and assure a good ring seal. A
7" or larger in diameter harmonic blancer instead of a 6" stock one can add more stability at
higher RPM. A high volume water pump can help keep the engine cool and add horsepower
(HP). The engine should be as clean as possible; gallery brushes are a good way to help clean it
in tight spots or holes. This is just some performance tricks to use that are easy that will help the
performance and looks of the engine.
When rebuilding or putting in a new mechanical part on the car, it should not go over 50
MPH (Miles Per Hours) for the first 500 miles and try not to do wide open throttle starts. Also
try not to make super fast stops (GMC 2). The engine oil should be changed every 3,000 miles
or 60 days whichever one comes first (GMC 12). Following these little rules should help the
performance and long lasting life of the car (GMC 2).
On a camshaft, bigger may sound better but not always better and it is best get the right
camshaft for what is wanted out of the engine. "Bigger is not always better, and a bigger cam
won't always make more power. It's no fun to roll up next to some newbie in the mild ride while
that Pro-Stock cam thumps away under your hood, only to have him leave you stumbling in his
dust when the light turns green." Also found out that smaller camshafts close the intake valves
faster, which gives the engine more compression. Choosing a camshaft may not be easy there
are a lot of camshafts out there (Petralia 71-75). They are designed for different functions such
as towing, gas saving, racing, nitrous, off road, etc. There are a lot of technical specifications
when choosing a cam like cam lift, duration, rocker arm ratio, valve open and valve close. A
camshaft can add up to around 80 horsepower and several different sounds. The timing chain
that the camshaft has stock is a nylon type gear, which might not take all the stress, rpm, and
horsepower that a performance engine is going to put out. There are several different types of
after market timing chains and gears.
Taking heads in for a different angle valve job, such as a 3-angle valve job will help the
valves seal better. Depending on the camshaft that was chosen its specifications may require
different valve spring tensions on the cylinder heads. If the camshaft specifies larger tension
springs the push rods have a larger amount of stress to open the valves. A good idea is to pick up
some harder steel ones or the stock ones might bend. Also the exhaust valves needs to be able to
take a lot of heat, it has to be able to take around 1,000 degrees without bending or warping so
stainless should be used (Autosite Report? 2).
Researching roller rocker arms, seeing how easy they are to install and how much they do
it would be hard to get along without them. Roller rocker arms do several thing to improve
performance like, reduce friction, faster revs, increase horsepower, increased reliability,
improved high-rpm, less valve train flex, lower engine temperature, change valve opening ratio,
and usually stronger than stock rocker arms. They make rocker arms out of several different
types of metals, designs, functions, etc. Get the right roller rocker for what is expected out of
this engine (Kiewicz 83-85).
Specifications for head bolts and main bearing bolts on a performance engine should not
be left out. Such as ARP (Automotive Racing Products) bolts that take more than stock. The
head bolts and main bolts take 170,000 P.S.I. (Pounds Per Square Inch) or more. This should be
enough to take the horsepower of this engine. The stock bolts will stretch and might brake when
under racing conditions.
Intake manifold, there are two main types of manifolds a single plenum and a dual
plenum. Single plenum manifolds are better for wide-open throttle, not as good off idle response
and has poor low torque. The single plenum manifolds are usually better for bigger engines e.g.
350-500 C.I.D. (Cubic Inches Displacement) that operate in the higher R.P.M. (Revolutions Per
Minute), (e.g. 2,300-7500 RPM). The dual plenum manifolds are better for semi-wide open
throttle response, and good low-end torque. The dual plenum intake manifolds are usually better
for the smaller engines (e.g. 283-350 C.I.D.) that operate at lower R.P.M. (e.g. 1,000-5,500
R.P.M). Knowing the after market manifolds (which are usually aluminum) take around 26
pounds off which would take off weight and would dissipate heat quicker thus making it lighter,
run cooler and faster. For a normal street machine it would most likely be best to get a dual
plenum and for a race car it would be better to get a single plenum. The Edelbrock Performer
R.P.M. manifold is a very popular manifold with the Hotrods that were at the car shows. A
lifter valley baffle (windage tray) helps keep the incoming gas as cool as possible by blocking
engine heat (Kiewicz 83-85).
With a performance camshaft and intake manifold. An after market carburetor would be
a good investment, which has a larger C.F.M. (Cubic Feet Minute). For most street cars a good
choice is 650-750 C.F.M. double pumper four-barrel carburetor. The Holley and Edelbrock
carburetors seem to be popular at the car shows. Stock air cleaners on cars seem to starve the
engine from air, which decreases horsepower. Adding a high-flow air-filter that lets the engine
breath more can increase around 7 more horsepower (Davis 6-19). Adding step spacers under
the carburetor can increase the power by around 9 horsepower and 23 foot pounds of torque.
They give the engine better high RPM's fuel mixtures and improve wide-open throttle response.
These usually reduce the carburetor strength. Increasing the jet size is a way to get around this.
A 4-hole step plate weakens the strength of the carburetor less than a wide-open step plate
The crankshaft does a lot for the engine. When selecting a crankshaft consider stroke
(how far the piston moves up and down), crankshaft metal, cross-drill (for oil), journal hardness,
and some other factors. Changing the crankshaft it can be setup for a stroke. This should change
the compression, timing curve, high or low horsepower etc. More compression is better for low
end and more is better for high end. Sometimes the crossed drilled oil holes are sharp. Consider
reliving these so they don't rub on the main bearings and wear them out faster.
When selecting a piston set also have to consider if the car is wanted to run off alcohol or
gas. Comparing Hyperuetectic pistons with current forged pistons. Some original factory
engines are made with Hyperuetectic pistons. Hyperuetectic pistons improve power, fuel
mileage, smog emissions, and reduce scuffing. Some manufactures focus on a lot of areas like
ring sealing dynamics, life of piston, different metals, no piston rock, peak cylinder pressure
timing, minimizing blow by (power flowing past rings), cylinder air tumble and swirl, increased
RPM ranges, weight, strength, added piston options and cost. If there is piston rock the life of
the piston and cylinder will be diminished. With a performance engine the lightest piston is best
but must not be too weak or it will crack. On a performance engine with increased RPM ranges
the need for some harder piston rings and connecting rods. There are three types of rings a
compression ring, gas accumulator ring and oil ring. Better piston rings take more impact, are
longer lasting, more reliable, reduce blow by and cylinder wear. Connecting rods are matched in
weight (balanced), less weight, shot peimed to reduce structural cracks and reduce stress thus
stronger, and more reliable.
Nitrous is two oxygen atoms and one nitrous atom. Nitrous oxide system (N.O.S.) is a
cheap and fast way to add power. Also have to watch out how much power is added to the
engine. A nitrous oxide system can add around 50 to 300 horsepower with a push of a button
(Magnante 77-83). Around 50 to 125 horsepower increase is what a stock V8 engines can take.
"Nitrous oxide gives lots of HP but you have to run the snot out of it" (Warrer 110-115). Which
means the engine will heat up fast and nitrous can melt some engine parts if too high or run to
long. Nitrous can make a major difference in power though. Nitrous oxide systems come in kits
and are matched to the amount of HP that is desired with installation that takes about one day
A good idea is to add a high volume oil pump to help keep the engine lubed up but there
are some exceptions that should be watched out for. An oil pump that pumps too fast can suck
an oil pan dry. If oil pressure gets to high it can flow right over bearings too fast and not pick up
enough heat. The engine should have about 10 PSI (Pounds Per Square Inch) of oil pressure for
every 1,000 RPM. A larger oil pan should usually be used with a high volume oil pan. If a high
volume oil pump is added there should also use some anti-pump up lifters. Which means when
the oil pressure goes up it does not make the lifter hard and not cushion the push rods/rocker
arms making the valve not close (seal) or to become loose and chatter. This should help stop any
rattling in a engine from the high oil pressure (Petralia 122-127).
An important factor is also having a decent ignition system because the factory ignitions
are not very performance oriented (Kiewicz 83-85). On a V8 engine that is turning at 3,000
R.P.M. at 70 miles an hour the engine is going to need 12,000 sparks per minute (4 sparks per
revolution). The coil changes the 12 volts on the Chevelle to 35,000 or more volts (Autosite
Report? 2). The ignition is that important explosion starting system. Better ignition gives more
spark energy, quickens throttle response, better fuel mileage, increases spark duration, reduce
exhaust emissions and improves idle and starting. Some distributors such as MSD (Multiple
Spark Discharge) distributor allows setting the distributor to the engines timing curve to match
the camshaft. Some ignitions may seem hard to install but they give some very good instructions
that will help out a lot. When buying a performance ignition a good idea might be to pick out
some nice spark plug wires. They have less resistance, take more heat and deliver more power.
Using headers instead of stock cast exhaust manifolds can improve fuel economy, better
sound, reduce weight, improve performance and reducing exhaust backpressure. Headers can
get around 1,300 degrees fahrenheit so high heat paint or some other type of coating to stop rust.
After a while chrome usually turns a blue color. If headers don't get painted they will corrode
and will be eaten on the inside and out. There will be a power loss from the corrosion on the
inside. Hooker Headers are a good choice (Smith 69). With the high performance engine and
the headers an optimal choice would to put on dual exhaust instead of single and some good
mufflers. They also help reduce backpressure, better sound, add horsepower and increase fuel
mileage (Kiewicz 83-85). Two-stage glass packs should sound good and have a good flow rate.
Feeding the engine its food (fuel) is a big part in keeping it alive (running). "In a fuel
system bigger is always better there is no over doing it." Volume and fuel pressure is not the
same. Some people think that if they increase the fuel pressure its the same as increasing the
volume. Sometimes the opposite can even be true. Placing a too high of a pressure fuel pump
can lead it to become necessary to buy a pressure regulator to turn back down the pressure.
Which is ok but is wasting money. If there is a problem don't blame the fuel pump right away.
Check it out and investigate it. There could be an undersized line, low voltage at the pump, bent
line, bad (dirty or clogged) fuel filter, etc (Kinnan 66-68).
The majority of car show cars look good and have very little rust. Nice polished, painted,
chrome parts really make a car look good and help the life of parts. A way to make the engine
look good is to get chromed or polished aluminum pulleys that look the same (Cole 103-114).
Covered hoses also make an engine look good and also help protect the hoses (Marlan 6-19).
Batteries look ugly and a nicely done battery box would look really good (Davis 6-19). There
are some nice rust inhibitors which make life easier when painting some parts (Petralia 76-80).
A transmission can be converted to approximately double its life. The B & M TransKit
will turn the stock transmission into B & M TransKit TH (Turbo Hydro) 350. This will allow
the transmission to shift quicker, more reliably, tow more, take more horsepower and torque.
When taking a transmission apart inspect it for any types of warn out or out of tolerance parts.
The transmission fluid should be changed every 12,000 miles (GMC 12).
Picking the correct torque converter is a hard choice because without the engine on a
dynamometer its best to make a educated guess on selecting one. Not knowing the true power
curve of the engine, the best way is to try following the manufacture of the camshaft
specifications and what is wanted out of the engine horsepower wise and the weight of the car.
So guessing it would be in the 2,000 to 3,000 (which most cars land in this area). Might consider
the gas saving side of an in between educated guess. Which would be a lower RPM torque
converter. Some where near the 2,000 RPM torque converter. If you upped the torque converter
by ten percent it would be like adding ten percent more power (LPE Drag Racing Tech Tips 1).
There are many different types of differentials such as limited slip, posi-traction, air lock,
etc. Also having to think about rear end gear ratios when doing a rear end. The limited slip uses
clutches to let the other wheel grip eventually. One wheel can spin and then the clutches lock
and spin the other so the car won't get stuck in that mud or sand (Limited Slip Differential 2).
Posi-traction is a differential that always turns both wheels evenly. Air lock is where one wheel
is free til an air pressure is supplied at the differential and locks up the differential so both wheels
turn. Also when taking a rear end apart make a good inspection of it for cracks, chips, bends,
worn or bad parts (Kiewicz 68-71). Should change the gear oil every 12,000 miles (GMC 12).
Rear end gears turn the engine power by ninety degrees and multiply torque. To find the
output torque multiply input torque times the gear ratio. High gears such as 2:72's (freeway
gears) would be very slow off the line and are not very stop light racing gears. Low gears such
as 4:56's (stop light gears) which would be about right for a Garfield (fuel eating) engine and
great for off the line. By dividing the ring gear teeth by the pinion gear teeth the gear ratio can
be found. Also is possible to find the RPM that your engine will be going by using this formula
MPH multiplied by transmission ratio multiplied by axle ratio then multiplied by 336 divided by
tire diameter equals the RPM (Freiburger 86-91).
It is a good idea to box in the lower trailing arms by welding a block of steel on the
opened side on them. It helps stop the twisting and turning motion and makes a better mount.
When having the trailing arms out a good idea is to use urethane bushings. They are a little
harder plastic than stock ones and will help stop wheel hop. Adding a swaybar can improve the
turning and also help stop wheel hop. If there is also severe wheel hop problems you could add
an air bag to the passenger side spring which could help. On a race/performance car there should
not be any wheel hop (Wilson 3). Every time the will hops the car loses traction, which means
horsepower is lost out of the power plant (engine). Another solution to wheel hop is to increase
the rear end spring size. Which will help the car bounce its weight when the car is started really
fast. Giving the rear end more traction and the Chevelle a more racy look. If there is no wheel
hop and the tires keep spinning a solution to that problem is to put wider tires on.
Someone might want to take the car to some car shows when it is totally finished. After
all this work is done to a car it should perform a lot better. Cost very little money for several
reasons. The car should work the way it was built and need little up keep. Time is need to
rebuild a car but in the end the car will be good as new and a lot cheaper than a new car. Fixing
up a car is a great learning experience and great accomplishment can be made like learning about
several things such as performance parts, performance techniques, assembly specs, making
things look nice, finding bad parts and replacing them.