Project Retro 5.0 is our modern take on the awesome time in the 1980s and ‘90s when the Fox Body Mustang was the king of the streets, thanks to its “modern” fuel-injected 5.0-liter engine. Based on the 8.2-inch deck height Windsor architecture that has powered Mustangs since their inception, the EFI 5.0 was a factory hydraulic roller engine that really was impressive for its time.
However, “its time” was thirty years ago. Since then, there have been a lot of improvements in engine technology, both in the OEM and aftermarket. While the original Cobras were hot stuff with 235 horsepower off the showroom floor in 1993, nowadays, we have GT500s making 760 horsepower with a warranty, and cracking the 1,000-horsepower mark with a few minor bolt-ons.
So, our plan, in a nutshell, is to do what they did in the ‘80s and ‘90s, but with today’s modern technology and knowledge, and see what kind of power we can make. Will the limits from back then — mainly the stock block and its fabled 500 horsepower failure point — still be the limits now, or will our modern engine controls get around that? We’ll find out. But first, we need to quantify a baseline.
The Starting Point For Retro 5.0
The main reason we need to get a current baseline, is because we’ve made a few concessions to the modern era right out of the gate, and a few improvements over stock parts. We are starting with the 5.0-liter engine out of a 1993 Thunderbird, which was rated at 200 horsepower using the SAE net standard. The block that came in the Thunderbird is an updated casting for 1991 — the F1ZE — but it has the same cast E7AE-AA 3.00-inch-stroke crankshaft as all the Fox Bodies
The connecting rods are factory-style forged 5140 steel pieces, which were purchased on Black Friday for $138, shipped… Let that sink in for a second. The rods only differ from stock in that the pin-end of the rod has a bronze bushing installed to make the .912-inch pin free-floating instead of a press-fit affair, and they are fitted with 8740 rod bolts. (The machine shop that balanced the rotating assembly thinks the rods might actually be the fuse that keeps the block alive; we’ll see.)
The pistons are really where the short-block assembly differs from stock, as we decided to start off with a good set of pistons right out of the gate. We used a set of Icon forged 2618 flat-top pistons in the build, which only brought compression up about 0.3 point, so nothing crazy there. We used the factory Thunderbird cam, which has less lift than the standard H.O. camshaft. The rest of the components, as you can read in the short-block article are new OE-replacement components, and the cylinders were hit with a few strokes of a 320-grit dingleball hone before being installed.
Up top, we are starting with the same bone-stock E7TE cylinder heads every 5.0-liter H.O. got, with their tiny intake and exhaust ports, tiny valves, and, well, tiny everything — except the valve spring retainers, those are huge. We topped it off with a factory Fox Body E7 intake manifold (man, those are pricey on eBay these days!), and everything sealed up with MAHLE O.E. gaskets.
While we are deviating from the strictest of the “SAE Net” definition, we are running a mechanical water pump and alternator in the testing, so it’s closer to SAE Net than SAE Gross. We’re also running a short-ram intake and cone filter, along with a 75mm throttle body and EGR plate. We are also using a set of unequal-length shorty headers designed for a ‘70-’71 Mustang and run quite tight to the block — no dyno headers here. All of which amounts to the mildest of bolt-on upgrades.
The most significant change from the original configuration is in engine control. While we do actually have an A9P computer in storage (don’t hoarder-shame me) we decided to start off right away with with a Holley Fox Body plug-and-play Terminator X kit along with big 78 lb/hr Deatschwerks fuel injectors. No 19-pounders and calibrated MAFs here.
Enough Talking; Dyno Time
Here’s where the story gets interesting. Once we got the engine all bolted up to KPE Racing’s dyno cart, Tommy had a family emergency. Instead of canceling our session, he tossed us the keys to the shop and said, “You guys have got this. If you have any questions, call me.” Now, thanks to the Holley Terminator X software and self-learning features, I wasn’t all that worried about tuning a stock-ish 5.0L combination myself. However, our Director of Content, Brian Havins, got a crash course in running the dyno, and he had the hard job.
It only took us a few pulls to find a rhythm in the dyno room, and thanks to the Holley EFI wizard, the base tune was pretty darn close. After a little bit of pretending to know what I was doing on the keyboard, we had a repeatable baseline number that wasn’t really changing much with additional changes. That number came out to be 255.3 horsepower at 4,800 rpm, and 321.4 lb-ft of torque at 3,500 rpm, in that familiar Fox-Body-shaped dyno graph. But wait, there’s more!
As we were getting ready to call it done on the baseline for Retro 5.0, I remembered that Brisk USA had sent over a set of the LGS plugs for me to compare to the standard Brisk Silvers I had in the engine. A quick plug swap and we fired up the dyno to find a consistent, repeatable 5 horsepower and 6 lb-ft increase in the numbers, with a new baseline of 260.5 horsepower and 327.7 lb-ft of torque.
A 60 horsepower and 52 lb-ft gain over the original 200/275 rating isn’t bad at all. However, now we have to wonder, are we going to see similar gains over what we expected out of a Heads/Cam/Intake swap from the ‘90s? Well, you’ll have to stay tuned for the next installment, because we’ve got a modern Twisted Wedge 11R top-end kit from Trick Flow we’ll be testing next time.