Pros and Cons of Repowering Classic Muscle Cars

Repowered and Modified 1979 Trans Am
Repowered and Modified 1979 Trans Am. Photo by Mark Gittelman

When you throw down your money on a muscle car from the 1960s or 70s the engine could be more than 50 years old.

When this power plant is in need of repair, many classic car owners are tempted to pull the original engine and replace it with a modern one. This is a tough decision for any car owner. Here we'll discuss the pros and cons of repowering a classic muscle car.

Modern Power in a Classic Trans Am

Pictured here is a classic 1979 Pontiac Trans Am. With the hood closed no one would know that an Ls3 has made its home inside the engine compartment. The owner fabricated a beautiful stainless steel bracket that holds the original shaker hood scoop in exactly the right position.

When the engine is running it has a nice little shake, just like the original V-8 had. However, this LS conversion turns the once capable muscle car into an absolute beast. Although I consider myself a purist and appreciate an automobile in factory original condition, I enjoy a ride in this TA.

Not only does the 6.2L Chevrolet crate engine produce 430 HP, it also brings modern reliability to this old Pontiac. Another thing worth mentioning is the 10 miles per gallon improvement in the fuel economy department. The factory installed 400 cubic inch V-8 pulled down around 8 mpg in a city driving situation.

Pros of a Modern Engine

Obviously the benefits of installing an engine manufactured in this decade are numerous. Here we'll review just a few of the advantages. On the ignition side of the equation, we get rid of the old-fashioned distributor. This means no more cap and rotor or points and condensers to deal with.

Instead we now have individual coil packs controlled by a DIS (Direct Ignition System). Not only is the DIS system virtually maintenance free, but it also provides a hotter spark that supports complete combustion. The modernized ignition system also allows us to use platinum spark plugs. This moves the spark plug maintenance schedule from three years or 30,000 miles to 10 years or 100,000 miles.

On the fuel system side, we eliminate the mechanical style fuel pump that puts out a miserable 6 psi of fuel pressure. In addition, this upgrade removes all the carburetor problems from our classic car. The modern style electric pump pressurizes the fuel rail up to 60 psi. At the end of the rail we'll now have modern style fuel injectors.

And just like the ignition system we reap the benefits of modern technology. Higher fuel pressure utilizing individual injectors provides increased control and better atomization of the fuel charge. In return we receive increased power output, lower tailpipe emissions and a boost in fuel economy at the same time.

Cons of Installing New Style Engines

I think the most glaring problem with yanking the original powertrain and replacing it with a modern version is we remove all measurable value from the automobile. A classic muscle car in factory condition can be a great investment when the originality is maintained.

As time marches on these vehicles become increasingly rare and values rise. With that said, installing a new style engine doesn't make the car worthless. It simply removes a standard measurement of the individual car's value.

Instead the car becomes worth what someone is willing to pay. On a well done conversion this can still equal a substantial sum of money. If you decide to pull the trigger on this upgrade you'll also have to rip up your invitation to compete in a survivor or preservation class car show.

Problems with Installing Modern Engines in Old Cars

Installing a modern engine in an older car comes with its share of problems. In many cases heavy modification is required. Using the 1979 Trans Am featured above as an example, the Pontiac engine compartment wasn't interested in accepting the Chevrolet crate motor.

Not only were the motor mounts in the wrong place, but the oil pan was also the wrong shape. Fortunately this is a popular conversion. In fact, an LS conversion kit is available for all generations of General Motors F body cars. This includes the 1979 Trans Am and the Chevrolet Camaro.

A replacement oil pan and the Sure-Fit cross member system cost the owner less than $1000. The kit turned an extremely complicated conversion into a straightforward operation. However, if you attempt this upgrade on an automobile that is not as popular you may have to work a lot of the inherited problems out yourself.