We know how it is—engines are expensive. You’ve spent a great deal of time planning, reading magazine articles, and mapping out exactly what your dream engine for your project will be. Saving your pennies goes slow with all that life nonsense like bills and mortgages or rent.

But there is good news! There is low-hanging fruit in your engine compartment that is guaranteed to work for any engine, no matter what family, how high or low performance, or even if it’s got lots of miles on it. As long as it’s got decent compression and no death rattles, it can make more power, sound better, and be a hell of a lot more fun to drive. And we’re going to prove it!

Our test car is the same ’68 Mustang used for our paint and body story in the May issue. Its un-rebuilt, original 289ci has never left the engine bay (neither has the trans nor the rest of the driveline for that matter), and has about 226K of daily driving on it. Despite that, it runs smoothly and quietly with no leaks or odd noises. We know the stock 289ci two-barrel was rated at 190 hp in 1968, but that was on the old rating system and with no accessories mounted. Who knows what a new one would have made when tested on the modern SAE scale, but we’re going to find out what this one can do 45 years later!

We’re not expecting a fire-breather or any kind of big numbers, but we are looking for real-world gains that will make the car more fun to drive while we’re working toward dropping in the engine we’d rather have. And to do that we’re going to use a realistic, budget-friendly group of “day-two” bolt-on performance parts matched to the size and operating range of our engine. For those who aren’t up on the slang, “day two” is a throwback reference to mods that would typically be made “the day after” it was brought home from the dealership.

Since our engine is bone stock, we’re going with the tried-and-true air/fuel/ignition/exhaust treatment weekend bolt-on recipe that has worked for hot rodders since the dawn of time. These are the mods that make the most sense to do together since they work as a system to increase the overall efficiency of the engine. At the end of a couple of days of wrenching, you’ll have an engine that’ll make more power and sound beefier, which will make cruising around and stabbing the throttle more fun since we all like to be heard as well as seen. And, it’ll provide oodles more eye candy when popping the hood at a show or cruise-in. There’s a lot to be said for that.

To make sure we were being as fair as possible, the Autolite was treated to a full rebuild prior to testing since a decade of being parked with fuel had left it pretty cruddy and full of varnish and residue inside.

Speaking of old fuel, after a decade of sitting it’s an absolute necessity to either swap or thoroughly clean the fuel tank to prevent contaminants from fouling things. We picked up a new tank from Mustang Country with a new pickup, filter, and rubber hose and cap connection, since it was rusted inside.

With fresh fuel in a clean tank and the Autolite 4100 tuned, we put the Mustang on the dyno at Swanson Performance in Torrance, California. Swanson specializes in late-models, but is happy to handle vintage muscle as well. Despite running like a sewing machine, the Mustang only wheezed out 119 hp at 4,100 rpm and flatlined until 4,500 where we stopped the pull. Torque peaked at 175 lb-ft at 3,000.

From Swanson’s, our Mustang went directly to Hahn Brothers Racing. After getting it on jackstands, job one was to remove the very old factory GT dual exhaust system. Old factory pipes will always have large reductions in diameter in the bends due to the way they are formed. Small reductions aren’t too bad on low performance engines, but in areas up and over the rear axles, the pipe can be reduced by .5 to .75 inch, which does make a difference.

Flowmaster makes perfect exhaust easy and affordable for most popular muscle cars with their American Thunder kits. The pipes are stainless steel for corrosion resistance and are a true 2.5-inch diameter all the way through, thanks to mandrel bends. Note that we chose the non-GT option with slight turndowns that will tuck the exits at the edge of the rear valance. The mufflers are the fabulous-sounding 40-series two-chamber.

The system assembles with slip-fit connections and heavy band clamps, or you can weld it solid. We prefer to keep the clamps since it makes disassembly of the system for service much simpler.

Log-style manifolds are a power killer on any engine, so you’ll never catch them on one of our projects! We went with Hooker Headers Comp Series ceramic-coated long tubes. They are cheaper in a painted finish, but we always opt for the ceramic coating for corrosion resistance. It’s well worth the extra investment since they can last a lifetime.

We’re not going to lie, it takes just the right combination of twisting and wiggling to get the headers installed without unbolting anything, especially when working from the floor, but it can be done. Jim Hahn has done this many times before and knows that once you get them at just the right angle, the Hooker Comp headers slide right into place and fit like perfection.

The one thing you do have to unbolt on power steering–equipped Mustangs is the power steering ram. This drop bracket from Hooker is required for clearance on the tubes. It’s an easy three-bolt operation. We picked up exhaust reducers (3 to 2.5 inches) from Team C Performance in Bellflower, California.