We’ve been promising you this teardown for a few months now, and it’s finally here. For a quick recap, Project Retro 5.0 started life as a 1993 Ford Thunderbird engine, with the idea to build it up just like they did back in the ‘90s, but with modern technology and parts. We freshened up the bottom-end with some Clevite coated bearings, a set of Icon 2618 flat-top pistons from UEM, a $138 set of Black Friday stock-style connecting rods, the stock crankshaft, and a Moroso main girdle.
Up top, we rebuilt the E7 heads with all new stock-replacement components from Melling, and found an old E7 intake manifold on eBay for way too much money. That was fitted with a BBK 75mm throttle body and EGR plate, along with a short-ram intake tube. The combination was run on a Holley Terminator X Fox Body plug-and-play ECU system on KPE Racing‘s engine dyno, and came in at 260 horsepower and 327 lb-ft of torque, not bad for the tiny T-bird cam and running accessories.
Once baselined, we ripped the top end off of it while on the dyno and swapped on Trick Flow’s 170cc 11R Top End kit on it, along with a classic Holley SysteMAX intake manifold. A simple heads/cam/intake (H/C/I in ‘90s parlance) gave us over 150 horsepower above the stock parts, and about 50 more horsepower than we would have typically expected from these parts back in the 1990s and early 2000s. The dyno’s final reading was 411 horsepower and 399 lb-ft of torque.
That would make for a killer street car engine as-is, that we would expect to live a long, healthy life backed up by our SN95’s Tremec TKX. But, we always want more. So, the next logical step was to do the same thing that everyone did to Fox Bodies back then — throw a Vortech on it. Back in the day, it would be an S-trim blower in the bolt-on Fox kit. These days, that same kit exists, but the head unit has been replaced by a more modern Si-Trim supercharger.
After our baseline dyno session with Retro 5.0, we knew we were going to have a stout performer on our hands.
Bring On The Blower
The supercharger itself is listed at a maximum horsepower rating of 775, so we assumed that we would have plenty of headroom to carry out a number of tests on the supercharged mill, down the line. With a super-safe tuneup in the Holley, the first pull saw 630 horsepower pop up on the dyno graph. With evil smiles all around, we knew it was game time (did I mention we were the only responsible adults on the premises at the time?). A little fiddling with the tuneup later, we were at 687 horsepower, and the limits of your author’s comfort zone, tuning-wise (without proper supervision, anyway).
A few days later, the real dyno operator/tuner came back, and started making pulls on the engine, in the hopes of at least cracking the 700-horsepower mark with Retro 5.0. Or cracking the block, whichever came first. The 302 block’s reputation was firmly in everyone’s minds after that very first supercharged pull, but we’ll all horsepower fiends. After a quick cleanup of the ECU’s fuel and timing maps, KPE’s Tommy Keeter firewalled the dyno throttle and let her eat. Keep in mind, the blower is rated at 775 horsepower, and that’s where we sized the fuel system at, with 78 lb/hr Deatschwerks injectors.
The Vortech Si-Trim supercharger is rated for 775 horsepower at it’s peak output. Obviously, they underrate them a little bit.
Well, Tommy found the limit of those at 789 horsepower. After a quick text exchange, we bumped up the base fuel pressure and tried for 800. The final number that day was 828.8 horsepower and 673.3 lb-ft on a stock 5.0 block from 1993. But, we weren’t done there. We had more pulls to make. Up until this point, all of the supercharged pulls had been made on BOOSTane’s Race E85. Now, we wanted to see what we could make on simple 93-octane pump gas with some of BOOSTane’s octane booster in it.
This obviously made less power on the same timing, due to the lack of cooling from the E85, but we still racked up the dyno pulls and made 787 horsepower and 648 lb-ft on the 93-octane plus BOOSTane Professional additive. As that testing concluded, this story starts. Because we were all a little concerned about how much power we made on a block that is storied to split itself in half at far lower power levels, we decided to tear the engine apart for inspection.
These are our peak power numbers on E85 and on 93-octane pump gas with BOOSTane Professional octane booster. Not to shabby at all from an off-the-shelf blower kit and a stock-block pushrod 5.0-liter engine.
The Moment Of Truth For Retro 5.0
We have heard stories about split 5.0 blocks that didn’t even know they were split, as the intake manifold and main girdle held everything together. So, part of us expected to get the lower intake manifold off and find a connect-the-dots pattern to have formed in the valley. As the intake came off, everything looked to be in perfect condition. So we soldiered on.
As the heads came off, there was a bit of a shock, but it wasn’t a bad one. Rather, the shock was how incredibly good everything looked. The pistons looked impeccable, the combustion chambers easily wiped clean. The real shocker was the condition of the head gaskets. Part of the Trick Flow top-end kit, I don’t think anyone ever intended them to seal at 800-plus horsepower-worth of cylinder pressure, but not only did they, but they looked absolutely reusable (not that we would ever condone such a thing).
It was time to flip over the short-block and look at the rotating assembly. The oil came out clean, the inside of the pan was free of any signs of distress. As we popped off the rod bolts, the bearings looked absolutely immaculate. The same was true of the main bearings after popping off the girdle and removing the crank. Upon visual inspection, there was absolutely no sign of any adverse wear. There was even still crosshatching visible in the cylinders, which was surprising, since the cylinders were just dingle ball honed previously.
Surprisingly, the bores were in mint condition and the head gaskets looked like they could be reused, not that we would condone such a thing.
Beyond The Naked Eye
The Mark 1 Mod 0 eyeball, as incredible as it is, isn’t really the best tool to detect microscopic (or even macroscopic, sometimes) cracks in cast iron. So, we used modern science to stack the deck in our favor a little bit. Goodson Tools offers a dye-penetrant crack detection kit that assisted us in our inspection. Mainly aimed at aluminum items, the Goodson Alumni-Chek Kit (P/N: AC-KIT) also works well on cast iron. The three-part kit consists of an aerosol cleaner, an aerosol dye, and an aerosol developer (along with five shop towels, which are an appreciated inclusion).
It’s simple to use the kit, as you simply clean the area to be checked. Then clean it again with the cleaner in the kit. Once the area is free from any contaminants, you spray on the dye and let it sit for a specified amount of time before wiping it off. The developer, as the name suggests, brings out any remaining dye, highlighting any cracks that might not be detectable to the naked eye and deep red lines.
The Goodson Alumni-Check system consists of three components. The first is a cleaner to prepare the surface to be checked. It needs to be free of contamination for accurate results. The second is a penetrating dye. That is sprayed on and left for a specified amount of time before being cleaned off the surface. The developer then activates any dye that has seeped into otherwise-invisible cracks and makes them visible to the naked eye.
Our first area to check was the main saddles, to ensure that there were no flaws. The clean-dye-develop process took about 10 minutes and revealed a clean bill of health. So we spun the block over and addressed the largest point of concern in the whole block — the lifter valley. The valley is the focal point of 5.0 block failures, so it was where we were most concerned. But, once again, it came back clean. As a sanity check, we performed the crack-checking procedure on a junk block in the shop and confirmed what a crack would look like.
So, that means our F1SE casting from Retro 5.0 is still in fighting shape. While this will definitely be seen in another project, it won’t bear the name Retro 5.0. As we’ve announced, we have big plans for Retro 5.0 Version 2, and it doesn’t involve any of the bottom end from this original Retro 5.0 build. Is that “myth busted” for the 500-horsepower limit on a factory block? Maybe, maybe not. The dyno imposes a lot less stress on the block than would be seen in a car at the same power level. So that might be it. Maybe it’s the fact that it’s an F1SE casting. Maybe we just got lucky. Regardless, this stock 5.0 block made way more than 500 horsepower and lived to fight another day.
With the area clean, and the dye applied and then wiped off, the developer brings out any cracks that might not be visible to the naked eye. Fortunately for us, there were no cracks in the valley if the engine, which was the source of primary concern.
