Ford Mustang Short-Block Engine Rebuild - Recession Special Part 1

Even you can build your own... 

   

  read full caption

Even you can build your own engine. But will it run? There's only one way to find out. Do your homework, and don't forget to install new freeze plugs in the block. You'll be hating life if you install your new bullet and have it spring a leak a little while later. Though the plugs may look good on the outside, once you remove them, the backside will show you why you're replacing them.

It Would be great if we all had 700-rwhp GT500s or 800-rwhp turbocharged, Windsor-powered coupes, but the reality is, most of us don't because we can't afford them. At the other end of the spectrum is the middle-to-lower-income enthusiast-the working stiff who has to save up for months to buy one single speed part. Most of us have been-or currently reside-in this situation, and with the escalating cost of fuel, among other necessities, money may be tight to spend on extravagant engine builds. That being said, we have a recession special designed for the average guy. It's a little more than stock, but not by much, and it won't break the bank-or your credit score.

Our subject vehicle for this build is the author's '90 5.0L, five-speed coupe. Purchased for a mere $1,500, it was in need of serious attention. With money so tight these days, this Pony has received more used and borrowed parts than anything else. It needed a set of head gaskets and an ignition module just to get it running properly, followed by a heater core/evaporator replacement and new front brakes. None of these items are exactly inspiring to an automotive enthusiast, but they were necessary if we wanted to be tooling around in a V-8-powered notchback. We scored some great deals on these replacement parts, and at present, have about $1,800 invested. It has proven to be quite reliable for the last six months, enduring an 84-mile round-trip commute each day.

This is our 143,000-mile short-block....        read full caption This is our 143,000-mile short-block. You'll want to start with as good a candidate as you can find. This will limit trips to the machine shop. Upon inspection, all of the bearings looked quite good with no copper showing through, save for the last main journal, but the minor amount of copper showing in the bearing and good condition of the crank journal gave us incentive to keep moving forward. As you remove the nuts from the connecting-rod ends, fit some rubber hose or tubing over the studs to prevent them from nicking the crank journals during removal.

The pistons shouldn't come...        read full caption The pistons shouldn't come out too easily, as a stock motor in good condition should still have good ring seal and some drag on the rings. Still, just a couple of taps with a rubber mallet or dead-blow hammer should do the trick. Inspect each piston's ring lands (where the piston rings reside) and piston top surface for any abnormalities.

Oftentimes engines with superchargers...        read full caption Oftentimes engines with superchargers can put added strain on the front crank bearing from the load applied by the tight supercharger belt. Our subject Mustang ran an ATI ProCharger for some time, but the front bearing looked great as you can see here.

Over the last two months, though, the car developed a slight knock in the bottom end, which is probably the result of the fresh head gaskets holding in the cylinder pressure better and forcing the stress towards the 169,000-mile crank bearings. We feel that the fuel mileage is rather weak at around 18 mpg, most of which is spent driving on the interstate at a leisurely 2,000 rpm. These cars were rated closer to 24 on the highway, so we think that the high-mileage missile suffers from inefficient tolerances, and we hope to pick up a bit more fuel mileage as well as power.

Things being as they are, your author doesn't have the bank to go out and buy a fresh short-block for this Pony, so we decided to throw in some new bearings, perform a quick hone on the cylinders, and fit some new rings to the factory-forged slugs. While the motor is down and out, we'll pick a mild and relatively inexpensive camshaft to liven things up a bit. We also hooked up with Thumper Performance of Orange Park, Florida, which offers some reasonably priced stock cylinder heads that, from what we've seen, are some potent performers once the die grinder has been set down.

We laid out the rotating internals...        read full caption We laid out the rotating internals on a table to inspect each piece before ordering our new parts. The pistons and connecting rods all checked out, as did the high-mileage bearings.

We have a parts washer at...        read full caption We have a parts washer at our shop here at the office, but a bucket and some purple degreaser will do the trick. We used a fine-grit abrasive pad to hand clean each piston and rod assembly.

Depending on how gentle you...        read full caption Depending on how gentle you are, most of the old piston rings will come off easily and without breaking. You can use a broken one, whether snapped by accident or on purpose, to clean out the ring land grooves. Make sure you tape them up as the edges can be quite sharp. Then, just scrape the ring inside the groove until you feel no hesitation when sliding it through.

The idea is to freshen the long-block to bring back that factory-fresh cylinder sealing. We'll do this by restoring the ring-to-cylinder-wall sealing, as well as the valve seal, the performance of the oiling system, as well as improving the induction (and the horsepower) on the cheap, all while showing you how to get the job done yourself. We'll top it off with a Cobra intake manifold, and we should end up with a powerplant that works with our 3.08 gears and makes nice power with our lint-ridden wallets. Of course, you could substitute a larger cam and aluminum heads for more power, but that will be up to you.

To minimize the amount of downtime that this commuter special endures, we opted to utilize a short-block that we already had lying around. The 5.0 mill is, oddly enough, of '90 vintage, as it came directly from the fenderwells of our former MM&FF project car ProCharged Pony. The bottom end did have 143,000 miles on it, but when it was pulled from the supercharged Mustang GT, it was in fine health with lots of oil pressure and making 473 hp to the wheels. Knowing its history and the fact that it was in good shape was all the impetus we needed to start with it rather than the knocking mill in the commuter.

Don't go through all of the...        read full caption Don't go through all of the trouble of putting new bearings and rings in an engine and not spend the $6.96 on the freeze plug kit (Advanced Auto Parts, PN 5703530), as you can't depend on previous owners/users to properly maintain a cooling system, or the factory to use rust-free plugs. Use a hammer, and tap one side of the plug with a screwdriver or punch. This will pivot the plug around so you can pull it out with a pair of pliers.	After degreasing the block...        read full caption After degreasing the block and hosing it down, clean the inside of each cylinder with WD-40 and a paper towel. You'll want to get as many contaminants out of the cylinders before beginning the honing process. Clean the lifter bores as well.	Here are three tools for the...        read full caption Here are three tools for the do-it-yourself engine-assembly process. The small thing to the left is a ridge reamer, which will remove the ridge at the top of the cylinder. Most 5.0Ls in good condition will not need this, and it should only be used as a last resort, as you can take out too much material and shape the cylinder like a funnel. The object to the right is what many refer to as a dingleberry honing tool, or more correctly, a ball hone. They make these in various abrasive compounds, and the one we had was finer grit. These are better suited to moly or plasma-moly piston rings, but our cast rings like a more coarse finish, so we opted for the stone-honing tool in the center.
If you look in the cylinders,...        read full caption If you look in the cylinders, you'll probably see remnants of the old hone that look like scrapes. These are called crosshatch marks. You'll want to duplicate them and the angle they cross (about 45 degrees) with the new hone. To do this, you'll need to vary both the drill speed and the speed at which you plunge the tool in and out. A slower drill speed will work quicker, and you won't have to move the drill in and out as fast. Use some 30-weight motor oil on the cylinder surfaces during the process. It should take less than five minutes per cylinder to remove the glaze or shininess of each cylinder wall and return it to a slightly rough surface (with the proper crosshatch). If you find you need to spend more time working the hone to take out the imperfections, you might need to have the cylinders bored out by a machine shop. If the engine was in good shape to begin with, however, this shouldn't be necessary.	This is one of the cylinders...        read full caption This is one of the cylinders prior to us honing it. You can see a slight glaze or shine to it, as well as some of the old crosshatch marks.	Here's the cylinder next to...        read full caption Here's the cylinder next to it after we got done with our drill work. Notice it has a fairly consistent and uniform dullness to it. The crosshatch is what holds the oil and allows for a proper seal between the rings and the cylinder walls.