Muscle Car Restoration & Performance Work

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Muscle Car Restoration & Performance Work

Copyright AA1Car Adapted from an article written by Larry Carley for Underhood Service magazine

As automotive technology continues to become more complex with each new model year, you may be longing for the "good ol' days" when engines had carburetors and distributors but no sensors, fuel injectors or computers. Most driveability problems were fairly simple to diagnose and only required a trained ear and a few basic tools.

Alas, those days are gone for good (except for NASCAR). Even so, you may have a classic car or muscle car from the 1950s, 1960s and early 1970s that needs some work. If you can't do the work yourself, you'll need professional help. Some repair shops specialize in muscle cars or a particular make or model (classic Mustangs, for example, or Corvettes). Others do this kind of work as a sideline to supplement their regular repair business. They may advertise at car shows or swap meets.

Working on these older low-tech engines is actually much easier that working on late model vehicles because the technology is much simpler. But it requires older service equipment that is mostly obsolete for today's engines: Timing lights, dwell meters, ignition scopes and distributor machines.

The most complicated things you'll have to deal with on older engines are the choke and carburetor. Early 1970s engines are also equipped with some emissions controls such as EGR valves and air pumps, and the carburetors were often fitted with "anti-tamper" caps and sealed idle mixture adjustment screws. But there are no converters on pre-1975 vehicles and no computers on pre-1980 models. Almost all of these older V8 engines are pushrod engines with flat tappet cams and timing chains. You don't have to deal with overhead cams (except for those on the super rare Ford 427 SOHC engines), timing belts, multi-valve cylinder heads or variable valve timing. Most of the blocks and heads were cast iron and contained enough meat to allow rebuilding and milling.

Due to their age, many older vehicles are now exempt from emissions testing. In fact, most 1968 and older vehicles are totally free from emissions regulations and testing, which makes them a popular choice for hot rodders who want to drive a real performance machine without running afoul of the emissions police.

Many restored muscle cars and classics are relatively stock appearing on the outside, but have
modified engines for more power, and modern suspensions and disc brakes for better handling and braking.
Restoration Parts

In spite of their age, you can still find plenty of stock and performance replacement parts for older engines, especially the more popular ones such as small block and big block Chevy V8s, 289/302 Fords and 351 Fords. Most aftermarket parts suppliers still carry inventory for these older engines as do many parts stores and warehouses.

Good used parts also are easy to find and cheap to buy. Take a stroll through any swap meet and you'll see piles of aluminum manifolds, big valve cylinder heads, old Holley and Carter AFB four-barrel carburetors, performance distributors, camshafts, exhaust headers and tons of other bolt-on goodies. Probably 75% of all the engine parts displayed at a typical swap meet are for small block Chevys. Ford parts also are plentiful, though not in the quantities that Chevy parts are, and older big block Ford parts are getting tough to find. Oldsmobile, Pontiac and Mopar (Dodge/Plymouth/ Chrysler) performance parts are also less common. And if you're searching for oddball stuff like a manifold or heads for an AMC, Cadillac or Studebaker, good luck!

One of the best places to search for hard-to-find parts is the Internet. Ebay Motors auction site has thousands of new old stock and used parts for sale. There are also hundreds of websites for specialty parts suppliers and sites dedicated exclusively to particular makes and models.

Big Spenders

Most of the people who own classic cars and muscle cars today are in their 40s, 50s or 60s and have plenty of money to spend on their baby. A lot of these people don't have the time, the tools or the know-how to do engine work, or if they do, they'd still rather pay somebody else to do the work for them. It's much easier for them to open up their checkbook than it is for them to open up the engine.

Many people will spare no expense when it comes to restoring a classic muscle car they cherish. They want it done right and are far more concerned about the results than the price. That is quite a contrast to your typical vehicle owner who moans about every dollar he has to spend on maintenance and repairs.

The typical classic muscle car owner today is a big spender who often brags about how much money he has poured into his beloved car or cars. Every dollar spent on repairs and restoration is another dollar closer to realizing his personal goals for the project. What's more, most of these cars are appreciating rapidly in value. That's why money spent on restoring, modifying or maintaining a classic muscle car is considered more of an investment than an expense.

Most of these cars are not used for daily transportation but are driven mostly for fun or for showing off. You'll see them in force at cruise nights, parades and car shows - but almost never see one in a Walmart parking lot (too much risk of theft, damage or vandalism). You also won't see them out when the weather is bad or there is salt on the streets. Most are garaged or covered and are pampered far beyond their utility as a means of transportation.

More Power!

Classic muscle cars have to live up to their reputation, which means plenty of tire-smoking power when the pedal is to the metal. Muscle cars by definition have a high power-to-weight ratio, yet some owners are never satisfied with things the way they are and always want MORE POWER!

Before we go any further, I need to point out the two basic types of muscle car owners: purists and gear heads. Purists want everything absolutely stock with matching numbers and OEM parts. They want the car to look and drive exactly the same as the day it rolled off the showroom floor. Many classic Corvette owners fall into this category.

Big Bad Blown Corvette. But how driveble is it?

Gear heads, on the other hand, want more performance, which means lots more horsepower, more chrome and billet aluminum parts under the hood, and maybe even something sticking up through the hood like a supercharger or tunnel ram manifold with a pair of 850 cfm 4bbl carburetors and a scoop. Gear heads want engine modifications that create more "wow" factor when people peer under their hoods. That is why they leave the hoods open at car shows and cruise nights, to show off their engines.

For those who want more muscle under the hood, the first step is usually to install a slew of bolt-on goodies: an aftermarket aluminum hi-rise intake manifold, a bigger four-barrel carburetor, an open-air cleaner, a set of four tube exhaust headers with low-restriction mufflers (glass packs or turbo-style mufflers), a hotter ignition system that may include a recurved distributor, higher output ignition coil and better ignition wires, and dress-up goodies such as chrome or aluminum valve covers, pulleys, breather caps, wire looms, braided hoses, etc. Aluminum radiators and polished alternators are big buck items that add even more "wow."

As the quest for more horsepower becomes more serious, you may want you to install a hotter camshaft, bigger cylinder heads and/or higher compression pistons, or maybe a bolt-on NOS system (nitrous oxide gives you more bank for your buck than almost any other modification). You may want the engine balanced, blueprinted and tweaked for maximum performance. Building performance engines requires a lot of know-how and machine shop equipment, so if you don't have a machine shop in your area that can provide the level of expertise needed, one alternative is to install a high-performance "crate" motor. There are purpose-built long blocks complete with hot cams and big heads (usually aluminum), and often include the intake manifold as well.

Factory performance crate motors are available from Chevy, Ford and Dodge performance distributors. Aftermarket crate motors are available from a variety of engine builders. The price of a crate motor is usually quite affordable compared to having an engine custom built, and it may include a limited warranty. A performance crate motor often doesn't cost much more than a stock motor.

Engine kits are another way to put an engine together, but the machine work will have to be farmed out to a machine shop. The nice thing about a kit is that it gives you complete control over the assembly. The downside is that you are also completely responsible for the assembly work if you screw it up!

Don't Forget Driveability

One thing to keep in mind when modifying or building an engine is that a car must be drivable to be enjoyable. A killer big block, 560-cubic-inch, 800-horsepower drag racing engine with a wild cam that is built for the strip may sound great, but it probably won't be a very streetable engine. It will certainly have the power to light up the tires, but it will also be a royal pain to drive in stop-and-go traffic. And gas mileage? Forget it!

Going overboard is probably the most common mistake most muscle car owners make when it comes to modifying a stock engine. Long-duration cams that make plenty of top-end power and create a loping idle also kill low-end torque and throttle response. A good street cam should have a power curve that runs from 1,500 rpm up to 5,500 rpm, not 4,500 to 9,000 rpm.

Reliability also becomes a concern as the power output goes up. Most V8 engines can handle an extra 50 to 150 horsepower without blowing head gaskets or throwing a rod. Most drivetrains also can handle moderate increases in power without popping U-joints, frying the clutch, blowing the rear end or trashing the transmission. But once you get on the high side of 400 horsepower, other modifications become necessary to keep things from breaking or failing.

When you make serious power, a stock block with two-bolt main caps may have to be upgraded to four-bolt mains. Stronger steel rods and chrome moly pushrods with stiffer valve springs may be needed to handle the loads and rpms. A larger radiator and/or supplemental electric cooling fan may be needed to keep the engine from overheating. A larger, higher pressure clutch, beefier U-joints and a stronger rear end may be needed to handle the torque. Bolt-on traction bars may be required to control wheel hop along with stiffer rear shocks and/or springs.

Upgrades also may be needed for the fuel delivery system. As the engine gobbles more gas, the stock fuel pump may not be able to keep up with the demand. A larger capacity, higher pressure pump may be needed and/or supplemented with an electric booster pump mounted near the fuel tank.

As compression goes up, so does the risk of engine-damaging detonation and preignition. The highest octane pump gas that's normally available is 93 octane, which is not enough to reliably handle compression ratios above 11:1. Octane-boosting additives may be needed to keep a high compression engine from pinging under load. The other alternative is to back off the ignition timing a few degrees - but that also reduces power.

Head gasket failures also become more common at higher power levels and compression ratios. Most stock head gaskets can safely handle 400 horsepower. For higher output applications, performance head gaskets with tougher combustion chamber armor and reinforcements are usually required. Above 500 horsepower, the cylinders may have to be sealed with copper O-rings to keep the pressure where it belongs.

Monster motors like this 502 cubic inch big block Chevy can deliver tons of torque on the street.
But the transmission and drivetain have to be beefed up to handle the increased torque.
Choosing a Performance Cam

If you want a hotter cam, choose wisely because the camshaft determines the engine's personality and power curve. Choosing the "right" cam for a particular application means taking into account how the vehicle will actually be driven, vehicle weight, gearing, type of transmission (manual or automatic), the engine's compression ratio, carburetion and cylinder heads. The best advice here is to follow the camshaft supplier's recommendations (don't hesitate to call the cam supplier for advice if you need it), and to install a complete camshaft kit that includes new lifters, pushrods, valve springs and retainers.

As you look through the various performance camshaft manufacturer's catalogs, you'll notice two things. The first is that there are many different cam grinds from which to choose. The more popular the engine (small block Chevy, for example), the greater the selection of cams that are offered. The other thing is that each grind is designed for a specific type of application, so follow the cam supplier's recommendations to the letter.

Performance cams typically have more lift and duration than a stock cam. The most common mistake that's made when choosing a performance grind is "over-camming" the engine. Too much lift and duration in an otherwise stock engine is a bad mismatch that may hurt performance more than it helps.

When comparing cams, the numbers tell the story. These include lift, duration, overlap, lobe separation and timing. The duration specs reveal the cam's potential for making power within a certain rpm range. Generally speaking, the longer the duration the higher the rpm range where the cam delivers its power. Short-duration cams are good for low-speed torque and throttle response (especially in heavier vehicles and those with automatic transmissions), while long-duration cams are better for high-winding engines that make lots of top-end power.

Cams with up to 220 degrees of duration (measured at 0.050" cam lift) are usually best for stock unmodified engines. Once you go beyond 220 degrees of duration, intake vacuum starts to drop and idle quality suffers.

Another spec that affects driveability is the relative timing of the intake and exhaust valves. This can be expressed either as "valve overlap" (the time during which the intake and exhaust valves are both open) or "lobe separation" (the number of degrees or angle between the centerlines of the intake and exhaust lobes). Decreasing the lobe separation increases overlap, while increasing the separation decreases overlap. Most stock replacement cams with durations of less than 200 degrees will have lobe separations of 112 to 114 degrees. Higher duration cams for mid-range performance typically have 110 to 112 degrees of lobe separation. With racing cams, you'll find lobe separations that range from 106 to 108 degrees.

Overlap occurs when the intake valve starts to open before the exhaust valve has finished closing. Increasing overlap can be a desirable thing in a higher rpm performance application because the outgoing exhaust actually helps scavenge the cylinder to draw more air and fuel into the combustion chamber. But too much overlap at low rpm kills low-end torque and throttle response by excessively reducing intake vacuum.

A nicely detailed engine compartment is an absolute must for a restored muscle car.
This one is a Chevy 409 with dual quad carburetors.
Carb Tuning

Adjusting the carburetor so the engine starts easily, idles reasonably well and delivers good throttle response (no hesitation) also is essential for a well-tuned muscle engine. Getting it right makes a huge difference in how satisfied a muscle car owner is with his car. The most common mistake that is made is to "over-carb" a street engine with a big carburetor that flows a lot of CFM but has poor throttle response and low end torque.

The most sensitive adjustments are the choke, idle mixture, idle speed, accelerator pump and jetting. Replacing a mechanical choke with an electric choke is usually a good idea on these older cars. The choke setting affects the starting ability of the engine as well as idle while the engine warms up.

The idle speed and mixture adjustments affect idle quality. If the idle speed is set too high, the engine will strain against the transmission when an automatic is put into gear. On the other hand, if the idle speed is set too low, the engine may stall or hesitate.

The accelerator pump squirts fuel into the venturis when the throttle opens. When adjusted correctly, it will prevent the engine from hesitating and allow a smooth transition from idle to part throttle or full throttle. The power valve provides additional fuel when the engine is under load.

Rejetting the carburetor changes the air/fuel mixture above idle. The trick here is to keep the mixture slightly rich, but not too rich because an overly rich mixture fouls spark plugs and hurts fuel economy. A lean mixture is most dangerous because it can cause preignition, detonation, burned pistons and blown head gaskets.

The most accurate way to adjust a carburetor is on a dyno with an exhaust analyzer and/or exhaust temperature probes. But you can do it the old fashioned way by test-driving the car, reading the spark plugs and color of the exhaust, and then tweaking the adjustments until everything feels and looks right.

If you are replacing a stock carburetor with an aftermarket performance Holley or Edelbrock carburetor, vacuum secondaries are better for a street-driven vehicle than mechanical secondaries. Most aftermarket performance carburetors are ready-to-run out of the box and only require final adjustments of idle speed and mixture. Rejetting may not be necessary if the carburetor is properly matched to the engine application.

Used carburetors cost less than new ones, but a gamble and often turn out to be more trouble than they are worth. A used carburetor must be cleaned to remove accumulated varnish and dirt, and then completely rebuilt to replace dried-out gaskets and seals and worn needle valves, accelerator pumps and power valves. A used carburetor may also contain "surprises" that prevent it from working properly. The previous owner may have changed the jetting, drilled out ports or made other modifications that probably won't match your engine's requirements.

Finally, the most satisfying part of doing classic muscle car restoration work is seeing a piece of automotive history brought back to life, and experiencing the sound, the feel and the performance of real American muscle.
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A Classic Ford Restoration Project

A few years ago, my son acquired a rust-free, low-mileage 1965 Ford Fairlane. This car had a stock 289 V8 with a two-barrel carburetor and automatic transmission, not exactly the makings of a muscle car. So with the help of some aftermarket performance goodies, including an Edelbrock manifold, 4bbl carburetor and Crane Cam, the tired old 289 was transformed into a peppy, yet drivable, engine.

My son used the car as a daily driver for a couple of years, then sold it on ebay. He loved that car because it was totally unique. The 1965 Fairlane was never a popular model, especially the four-door sedan, so very few of these cars are left today. Most of the surviving '65s are the sportier two-door models, and only a handful of these are equipped with the high-performance "k-code" 289 engine. Fortunately, engine parts are still easy to find because the 289 is the same engine that was used in the Mustang.

High Performance Engine Building:

Carburetors
Mechanical Fuel Pumps
More About Camshafts & Choosing a Camshaft
Basics of Supercharging
Turbocharger Diagnosis & Repair
High Performance Pistons
Piston Rings: Stock & Performance
Engine Repair Options
Engine Rebuilding Tips
How to Rebuild Engine (replacing internal engine parts)
Engine Replacement Issues
Performance Mufflers
Muffler (How to Replace)

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