In this chapter I cover the common engine swaps for first-generation Mustangs that increase performance potential. My philosophy is “There’s no replacement for displacement” when it comes to increasing performance, but the key is how you get it. I discuss the tradeoffs of various options along with how good a given scenario is in terms of “Bang for the Buck” for the installation/conversion phase and once the car is being driven.
This Tech Tip is From the Full Book, FORD MUSTANG 1964 1/2 – 1973: HOW TO BUILD & MODIFY. For a comprehensive guide on this entire subject you can visit this link:
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I cover the following engine choices: small-block Windsor (shortdeck and tall-deck), big-blocks, modular engines (two-, three-, and four-valve V-8s; no V-10s), the 2011 and newer 5.0L Coyote engine, and the 2013 and newer 5.8L S/C GT500 engine. (No installations in original 351 Cleveland, 427 SOHC, or Boss, etc., vehicles are discussed, nor are these engines discussed as swaps.)
Given enough time, skill, and budget you can swap just about any engine into any car but that’s not what I address here. My goal is to discuss reasonable, practical, and cost-effective options most owners want to and can afford to install. These options are feasible and deliver meaningful performance increases with few, if any, significant tradeoffs.
For a daily driver the pushrod Windsor engines are really the only reasonable option unless your car already has or had a big-block. Upgrading to a big-block or to one of the modular or Coyote engines is really only practical for streetperformance vehicles where the desired performance level, novelty, and budget are the guiding factors. For a streetable track-day car the intended type of on-track/strip use likely dictates the tradeoffs between weight, power, suspension, and driveline design, usually with less regard for total cost.
In any case, you should retain the ability to use the car however, whenever, and wherever you want. This is about hot rodding for the masses, not just the monied few.
The small-block Windsor engines are by far the easiest to swap into first-generation Mustangs. Because these engines were originally available in these cars it’s a natural fit, except for the tall-deck engines in the 19641 ⁄2–1966 cars. Even that combination can be made to work without too much trouble, though it’s debatable if it is really beneficial.
The short-deck engine has plenty of room in the 1967 and later cars because they could be bought with big-block engines. The short-deck (8.2 inches) Windsor small-block engines ranged from 289 to 302 ci as original equipment in firstgeneration Mustangs. With the exception of a few special high-performance models most were simply designed to be light yet compact and reliable. Because the same basic engine layout was used well into the 1990s for the Mustang and other Ford products it’s clear the basic design was a very good one. However, when higher performance is your goal it’s often likely you expose shortcomings (thin walls, lack of reinforcements, etc.) that would rarely show up in normal use.
There are no hard-and-fast rules and no guarantees; every upgrade situation is different. A common belief is that a stock/OEM Windsor 5.0L block is good to about 500 hp in naturally aspirated form. Older 289/302 blocks (with the exception of the 1969/1970 Boss 302) are generally not as good to start with as the later 5.0L blocks for a number of reasons, not the least of which is they are not compatible with later OEMstyle hydraulic roller lifters.
If you’re going to use a power adder, you should at least upgrade to the superior Mexican, A302, or Ford Racing Boss 302 block. They have better metallurgy and reinforcements, which makes them stronger. Above 600 hp and/or heavy increases with a power adder, the A302 block should be the minimum considered. Realistically, it’s then time to upgrade to a stronger aftermarket block such as the Ford Racing Boss 302, or an even stronger version from another supplier.
The short-deck Windsor block has received a lot of support in the aftermarket because it fits easily in any of the first-generation Mustangs as well as later versions to the 1995 model year. Dart Machinery is one of the most respected producers of aftermarket Ford engine blocks (as well as crate engines, cylinder heads, and related items). Their products benefit from many advances beyond the original OEM designs.
For the Windsor family Dart offers four levels of engine blocks and any short-block, long-block, and complete crate engine based on them. These products range from the relatively affordable entry-level SHP blocks to the Iron Eagle variants to the all-out Race Series aluminum blocks. All are available in short-deck (8.2 inches) and tall-deck (9.5 inches) versions.
The SHP version is an iron block, which accepts most stock components and accessories, including the roller hydraulic cam setup (lifters, dog bones, and spiders) from 5.0L and similar EFI engines. It features thicker deck surfaces, scalloped outer water jackets (for better, more-even cooling), a priority main oiling system, steel main caps (four-bolt/ splayed on numbers-2, -3, and -4), and blind-tapped head boltholes (to reduce water leaks).
These blocks are available in short-deck and long-deck versions with siamese-bore diameters of 4.000 or 4.125 inches (unfinished). The cylinder walls are cast extra thick to allow for bore diameters of up to 4.185 inches while still minimizing bore distortion.
The Iron Eagle Sportsman shares most of its specifications with the SHP and adds a few features. The most significant of these is the option for multiple deck heights, which (in the tallest deck version) can allow for displacements of up to 468 ci due to its even thicker cylinder walls (.250-inch minimum versus .230-inch minimum for the SHP) and superior alloy (versus the SHP). These blocks are also available with 2.249- or 2.749-inch main bearings.
Dart’s Iron Eagle blocks are intended for hardcore racers yet they still retain compatibility with most stock components. These blocks build on the specifications of the Iron Eagle Sportsman blocks by adding a lowrestriction priority main oiling system along with front and rear external oil feeds to complement the complete stock-type system. Dual crossovers have provisions for restrictors to allow more precise allocation of oil flow when solid roller cams and/or roller rocker arms are used. Reducing oil flow to the rockers, for example, can reduce crankcase windage.
Other reinforcements include use of a premium alloy along with extrathick deck surfaces, even thicker cylinder walls, extra webbing in the main bearing area, and the use of billet steel four-bolt main caps for all five main bearings.
The short-deck version easily fits in all years from 19641 ⁄2 to 1966 because it’s virtually identical in its outside dimensions to what these cars originally came with. It can make more than 500 hp and still have great driveability. Short-deck blocks are a platform that provides ample power for most early Mustangs. This engine family is suitable for the 1967–1970 models but in many cases they don’t provide sufficient torque and horsepower for the larger, heavier 1971– 1973 models.
Aftermarket blocks can be stroked to 347 or even 363 ci to make enough power even for these cars. The 19641 ⁄2–1966 cars readily accept the shorter deck. You may have header fitment issues and this may require notching the header tubes. In addition the steering box and rod may have to be relocated when squeezing the tall-deck version into the smaller, narrower engine bay of these years. You’re also relatively limited by tire size (as to how much power you can effectively get to the ground), unless you make some relatively extreme modifications to at least the suspension and body.
The short-deck block provides a light engine package in a relatively lightweight car for improved handling. The tall-deck block weighs about 80 pounds more than the short-deck version (cast in iron) and in most cases the extra output it provides really isn’t usable in these smaller, lighter cars. You can stuff a tall-deck engine into the earlier cars but unless you modify/ remove the shock towers you have to settle for a less-thanoptimal exhaust system.
Hood clearance is likely also an issue. For the 19641 ⁄2–1966 cars a short-deck small-block is usually the best overall choice. If you want more power it is easy to modify one to 500 hp or more if you stroke it and/or use a power adder. Unless you’re building a competition or show car that’ll likely do.
For 1967 and later models, the tall-deck (351-based) Windsor may make more sense if you want to reach higher performance levels than are possible and/or practical with the shorter deck. The extra weight of the taller deck is less of a factor because these cars are heavier anyway, are suited for these engines, and you need more power for similar performance. Up to 500 hp you can still go with a stroked (347-ci) short-deck block and save some weight while also having a bit better selection of parts. For more than 500 hp with the short-deck use a power adder or step up to the taller deck and live with the weight penalty. You can, of course, also invest in an aluminum tall-deck block and get the power without much weight penalty, for a price.
A power adder on a stroked talldeck can yield 1,000 hp or more. You still have a car that’s completely driveable on the street, except perhaps under harsh weather conditions. It all depends on what your goals and preferences are and what resources (time, skill, budget, etc.) you have. A modified 351-ci tall-deck engine can get to 600 hp without too much trouble and it can spare you the expense of the new crankshaft and other parts (rods, pistons, etc.) needed for a stroker. This really only applies if you already have a tall-deck block because there’s little difference in price between comparable crate engines, either short- or tall-deck.
Installing a big-block in a 19641 ⁄2– 1966 Mustang is very difficult because the vehicle was essentially a pony car and not a muscle car. Physically the 390 FE and 385-series big-block engines are difficult to fit and you also need to upgrade the transmission, rear axle, differential, and other parts. It makes very little sense because the cars weren’t available with them from the factory and you need to remove the shock towers to make one fit. This requires substantial modifications and comes with quite a price tag.
You can make just as much power with a tall-deck Windsor with a power adder (not that you could likely use it effectively unless you also beefed up the body and suspension). A stroked Windsor can provide comparable performance with lighter weight. You also pay an ongoing penalty in lower stability, lower gas mileage, and even a reduced ability to make further modifications because you don’t have room for them and/or there aren’t many parts that fit this setup.
Installing an FE or 385-series bigblock in a 1967 or later car, on the other hand, is a practical and feasible option. Because these later cars were available with big-blocks from the factory they have enough room for them (most, anyway) and there are plenty of modifications and parts for this combination. You’d still be better off with a tall-deck Windsor (whether stroked or not) in terms of cost, lower weight, and greater parts availability but if you want a bigblock (for whatever reason) it at least makes some sense in these later cars.
If your 1967 or later car wasn’t originally equipped with a big-block you can get the parts for one from a salvage yard or as new parts from aftermarket sources. Depending on your goal special aftermarket parts such as motor mounts can provide added strength, lowering and/or moving the engine back, and so forth to help improve performance and resolve issues such as hood clearance with certain manifold/carburetor setups.
If you’re going for a particular look when you pop the hood, a particular sound when you get on it, or if you’re trying to build a clone of a special big-block model, for example, a big-block in a 1967 and later vehicle may make sense. It goes in easily and can be a cost-effective upgrade relative to a small-block or even the original big-block if it is an engine with lower displacement or lower performance.
On paper, the modular 4.6 looks attractive: aluminum block (mostly); aluminum heads in two-, three-, or four-valve configuration; plus lots of other features such as cross-bolted mains, overhead cams, and roller followers formerly seen mostly on more-exotic and/or racing engines. The two-valve versions are generally regarded as being the least desirable of the modular engine family in terms of their performance potential.
The biggest impediment to installing a modular engine into a first-generation Mustang is not the performance potential of these engines but rather their size and bulk, particularly in terms of width. The numbers (according to Ford Racing) tell the tale: A short-deck Windsor is 183 ⁄4 inches wide, the tall-deck is 21 inches, regular big-blocks (no SOHC, Boss 429, etc.) are about 26 inches, and the SOHC (two- and three-valve) versions of the 4.6L modular engine are 255 ⁄8 inches. They’re almost as wide as the big-blocks! The four-valve modulars are a whopping 30 inches wide.
All modular engines are about 28 inches long; a big-block is about 32 inches long.
Differences in height are really hard to quantify because there are so many differences in oil pans, intake manifolds, carbs versus EFI, etc. In general, Windsors are shorter than the 4.6L SOHC and the 4.6L DOHC is the tallest of this bunch.
Modular engines are significantly wider than all of the Windsors and can sometimes even exceed the width of a big-block. This virtually disqualifies a modular engine from being a practical choice for 1965–1966 cars (unless time and cost are not issues).
Then there is the questionable rationale of trying to install a DOHC modular engine in a 1967 or later car when even a big-block would be an easier (and likely less expensive) fit.
In any case, the modular engine’s reduced displacement relative to an older pushrod engine is something of a disadvantage, as is the initial cost of the engine and the reduced availability of performance parts. Furthermore, unless you convert to carburetion and some form of aftermarket ignition system to replace the OEM fuel injection, you also have the added difficulty of installing and tuning the full factory computer system or an aftermarket substitute for whatever you might choose to not retain.
A stroked tall-deck provides more displacement, greater performance potential, easier installation and tuning, generally lower overall cost, and even lower weight if you go with an aluminum block, heads, and intake.
Again, the numbers tell all: an iron-block 4.6L 2V weighs about 500 pounds; the 4.6L DOHC engines (all are aluminum blocks) weigh about 425 pounds. This compares to roughly 400 to 450 pounds for a short-deck Windsor with a production iron block and aluminum heads (more with an upgraded/ aftermarket iron block, and about 60 pounds less with aluminum block) and about 600 pounds for an all-iron tall-deck (550 with aluminum heads, and 470 for block and heads). Bigblocks weigh well over 600 pounds, even with aluminum heads.
The lightest option by far, an all-aluminum short-deck, is the easiest to install and is capable of making more than 500 hp naturally aspirated (much more with a power adder). Even if you forgo the aluminum block to reduce costs (by $4,000 or so) you’re still at the low end in terms of weight (more than the aluminum DOHC, but less than the iron DOHC).
Although an all-aluminum talldeck may not be the most economical choice, it arguably offers the greatest performance potential with relatively easy installation while still likely being lighter than the iron SOHC. A modified DOHC with a power adder can probably match a strokedaluminum tall-deck in output but it is significantly harder to install, less reliable, and likely costs more.
The 4.6L 3V engine produced a respectable 300 to 315 hp while weighing 420 pounds. The 3V engine is a better candidate than the 2V in terms of maximum performance potential while offering comparable performance to a stock, older 4.6L DOHC with significantly easier installation. A modified 4.6L DOHC can provide greater maximum performance than the newer 3V but the durability and reliability of the former is somewhat suspect (there have been problems with the earlier thinner castings, bore distortion, etc.). It is surely a more difficult fit in a first-generation vehicle, even with notched shock towers. In many cases the shock towers need to be removed altogether and a completely new front subframe and suspension is needed to make either of them fit.
Although the 5.0L 4V Coyote engine is technically also a member of the modular engine family it needs a separate discussion. The Coyote was introduced as the standard engine in the Mustang GT; beginning with the 2011 model year there are many more of them in circulation. Their cost is less because of the lack of a supercharger. They are also significantly lighter (only about 450 pounds) due to their aluminum block and dimensions similar to the previous 4.6L SOHC engines (a little wider at 28 inches, a little shorter at 26 inches, and about the same height). The good news is that they were rated at more than 412 hp (444 hp for the Boss 302).
Because this engine is so much more sophisticated in terms of its degree of electronic control it’s even more difficult to make everything work together because every car is different. The older vehicles just don’t have most things the newer ones have.
For example, if you use the original unmodified factory wiring and computer you have the most trouble. Ford Racing does sell a stand-alone Control Pack for vehicles with manual transmissions (for more than $1,000). This product includes a specially calibrated computer, the necessary driveby-wire throttle assembly, a mass air sensor and inlet tube, a modified body harness (with a power distribution box and certain features omitted for use in non-emissions vehicles including the correct oxygen sensors), and other items. You need to ensure the vehicle has the proper fuel supply system (with a return line) and hook up everything else that’s needed.
Even when you’re done with the install and you get the car running, you have to do a full tuning and calibration exercise to get anywhere near the level of performance and efficiency the engine had in full production form. Unfortunately, you’ll likely never get it that good because all of those things that were deleted to make the engine compatible in an older car were also things that helped it run better. When you change the components, change the vehicle (weight, gear ratios, aero, etc.), and remove some of the functionality of the computer (to not have it go into fault mode or throw trouble codes because many signals aren’t there) you just aren’t able to get it to run as well.
In time, the aftermarket will likely develop stand-alone computers and other components to resolve this problem, to some extent. But for now, there’s no doubt a pushrod Windsor is easier to install and less expensive with more performance potential.
Assuming that you’ve decided what type of engine you want, the next logical decision is how much work you want to do. Do you already have an engine that you want to overhaul and/or modify or do you want a new one? If the latter is the case you should very seriously consider the option of buying a ready-to-install crate engine rather than buying parts and/or a used engine, which would need to be worked on to be ready for use.
Crate engines are available from many companies, including Ford Racing, CJ Pony Parts, and Coast High-Performance. A crate engine builder that has been around for any signifi cant length of time (such as Coast High-Performance) has a wealth of dyno data and has established what runs well on the street and what lasts—and what doesn’t.
Companies such as Dart, Ford Racing, and CHP can afford to invest in the best equipment, people, and processes. This helps ensure high quality throughout the manufacturing and assembly process. This also combines the precision and consistency of CNC machining (which is far beyond what most engine shops can afford) with the expertise of a dedicated engineering staff and trained assemblers.
Special services such as multiangle valve jobs, precision balancing and blueprinting, and deck-plate honing are generally done at extra cost when having an engine built at a shop. The crate engine builder can incorporate many, if not most, of such operations into their normal processes so every engine gets some degree of “special” treatment at a signifi cantly reduced cost and with greater precision and consistency.
As you know, engines and other assemblies are available in various combinations for different uses and budgets. Most builders have what you need in stock so there’s little delay before shipping your order, even custom orders.
There are many processes included in the way a 347 (shortdeck) short-block is assembled. Following are photos of some of the unique features and techniques Coast High Performance (CHP) uses, many of which they’ve learned over the years from their thousands of engines already in use.
Before CHP chooses parts they have been thoroughly researched, developed, and proven over the years to provide better performance and durability for the customer. They also try to minimize the potential for any in-use failures or warranty issues that would damage their reputation, not to mention their bottom line. CHP keeps learning and improving so both they and the customer benefit.
V-Belt versus Serpentine-Belt Systems
Stacking multiple belts next to one another for various accessory combinations adds weight, complexity, and overall length to the engine. The extra accessories require the mounting brackets be adjustable as well, thus making them inherently less stable.
The solution to these issues is a single “serpentine” belt. This multiribbed belt is much thinner than a V-belt so it’s less affected by higher belt speeds. The multiple ribs increase the contact area of the belt relative to the pulleys, thus reducing the possibility of slippage. The single belt is made from better materials and is much stronger in terms of tensile strength, thus greatly reducing belt stretch during operation and over time. Serpentine systems are dynamically self-adjusting, thus providing stable belt engagement with less chance of coming off or breaking. The single belt also makes a shorter engine.
Vehicle manufacturers have almost universally abandoned V-belts in favor of serpentine belts for the primary drive of engine accessories. Unfortunately, most production systems are not easily retrofitted to older engines. Ford’s small-block Windsor engines are a notable exception to this in that the serpentine belt-drive system used on later-model 5.0L V-8 engines usually can be adapted to older engines with V-belts.
S.Drive Kits, for example, from Eddie Motorsports are available for conversions with or without power steering in several finishes ranging from a natural/polished look to gloss or matte black. These kits include everything needed for a conversion including a new alternator, water pump, power steering pump, and all associated pulleys, brackets, and other hardware. The cost is very reasonable and installation is fairly simple.
The result is a better-looking single-serpentine-belt system that reliably handles higher belt loads and RPM without needing periodic adjustment. The mounting of the components is much more stable and the packaging envelope of the drive system is reduced.
Written by Frank Bohanan and Posted with Permission of CarTechBooks