The short-block is the foundation upon which every killer engine project is built. If it’s not up to snuff, then all of the subsequent testing and components are going to provide subpar results. So, to that end, we were faced with a challenge with the Retro 5.0 project. As we’ve mentioned in previous articles we wanted to try and stay true to how the engine was delivered in 1993. However, in the subsequent 29 years, a lot has changed.
Plus, a few of the OEM parts have been proven to not be ideal for our ultimate goals for the engine. So, rather than risk a parts failure that might end the whole project early, we decided to do our best to balance quality components with the spirit of the build. Follow along as we take a look at what we did for the short-block.
Laying The Foundation
We’ll address it upfront — yes we know the 5.0-liter blocks have a reputation for splitting at the 500-horsepower mark. The exact reason for it is still debated to this day, and there are some people on the internet claiming to be making well in excess of that power for multiple seasons of racing. So why not see what we can do with the stock block.
The block is an F1SE-BB casting out of a 1993 Thunderbird. As we got it, the factory crosshatch was still visible. However, a check with a profilometer at Total Seal showed that the cylinders’ finish needed some love. Since the bores measured 4.001 inches, and the mains were all in-spec, we decided to roll with it, as-is and just hit the cylinders with a ball hone to give it some fresh crosshatch.
We tossed out the factory bearings, and instead, opted for our first modern upgrade — MAHLE performance bearings. We knocked out the OEM cam bearings and installed a set of Clevite SH-1321S performance cam bearings so that we wouldn’t have to worry down the road. We also opted for Clevite’s coated H-series main bearings in the standard size, since everything was within factory spec. The same went for the coated and narrowed rod bearings from Clevite.
We dropped the factory E7AE-AA 3.00-inch stroke crankshaft into the bearings, after having BC Auto Machine rebalance our crank. After doing the math on having the factory rods bushed for a free-floating pin, we ended up snagging a set of factory-spec 5.090-inch forged 5140 rods from Speedmaster during their Black Friday sale for significantly less than the cost of bushing the stockers. Plus, they had a set of ARP 8670-steel rod bolts. BC Auto Machine threw them on the hone and only had to open them up half a thousandth.
Our first fundamental divergence from the “stock” theme was with the pistons. Since the engine came with cast hypereutectic pistons, we decided to upgrade right out of the gate. We went with a set of ICON 2618 forged flat top pistons, in the stock 1.608-inch compression height and with the company’s M42 skirt coating. If you’re at all curious about using a 2618 piston in such a mild combination (to start), check out the article where we discussed that.
Besides the benefits of a forged piston, we had enough piston-to-wall clearance right out of the gate to work with the 2618 alloy, and when we get wild with the engine, we’ll already be set with the proper alloy. Plus, the flat-top design (the large valve reliefs measure 5cc) will add a little bit of compression over the factory design. (ICON actually makes a piston in their Formed Head Relief [FHR] series, but the four-relief design would have cost us compression.)
The ICON pistons came with .912-inch tool steel wrist pins, secured with a single spirolock, and a 1/16-inch, 1/16-inch, 3/16-inch ring pack. The top ring is a positive twist plasma-moly-coated ductile-iron ring, while the second ring is a reverse twist cast-iron ring. The oil ring is a traditional stainless steel standard tension affair. With the core specifications of the rotating assembly unchanged, we maintained the factory 302 cubic-inch, 5.0-liter displacement (which is actually slightly under those numbers).
Another concession we made in the name of reliability was the addition of a Moroso main support girdle. Designed to tie all of the main caps together and provide some additional strength to the block, the Moroso piece is machined to work with stock main caps right out of the gate, and fit under a stock oil pan.
The kit also has the benefit of coming with ARP main bolts, slightly longer than usual to account for the additional thickness of the steel girdle. The girdle is also designed to clear factory or Melling aftermarket pumps, although we did find that one of the ARP bolt heads just barely touched the oil pump. That was an easy fix.
For the oil pump, Melling has long been known for its M-68 and M-68HV oil pumps in the Ford arena. But for this project, we opted for the high-performance 10687 oil pump. It’s a standard-volume, standard pressure pump that comes with an optional spring for additional pressure. The performance upgrade design over the M-68 comes from an improved gerotor set and increased strength and support for the oil pump driveshaft, built into the housing. If that doesn’t fit our “traditional upgrade, but with modern technology” theme, I don’t know what does.
While the 10687 uses the OEM-style pickup tube, the Moroso girdle occupies the space where the OEM pickup tube resides. After a brief gameplan to start cutting and welding the OE tube, we realized that Moroso makes a pickup tube specifically for the girdle. The 24518 pickup bolts right up to Melling’s entire line of SBF pumps, and drops right into place, putting the pickup screen exactly in the factory location.
As you might have seen we opted for a stock-type replacement oil pan from Milodon. As we alluded to in that article, part of the reason we wanted something that used the stock pickup, is because the girdle-specific tube mimics the stock pickup’s location. Plus, it really fits the theme well, and that gold irradiated finish is just gorgeous. Milodon also supplied us with their complete engine fastener kit, which includes a set of high-quality oil-pan bolts.
That, combined with MAHLE’s oil pan gaskets made for an easy installation. However, you’ll notice that we haven’t fully installed the oil pan. That’s a little hard-learned lesson we picked up a while back when we dropped something into an oil passage with the pan fully installed, and while that “thunk” was the most beautiful sound ever, knowing it passed right through the oil passage, pulling the pan off was more work. Now, we just wait until the end of the build to bolt it on.
The Brains Of The Operation
For the camshaft, we stuck with the OEM T-Bird cam (F3ZE-6250-CA), for a couple of reasons. First, the ’91-93 Thunderbirds actually came equipped with the same camshaft as the ’93 Cobra. While technically the Cobra uses a T-Bird cam (but with 1.7:1 rockers), it sounds a lot cooler to say it’s a “Cobra cam.” The cam itself specs out at .282 inch of lobe lift on both the intake and the exhaust (which works out to .451 at the valve with the 1.6 rockers) along with 209 degrees of duration at .050-inch of lift, with a 118-degree lobe separation. Not the stoutest specs, but a great starting point.
To keep the cam in sync with the crankshaft, We opted for a Melling billet-steel 9-way adjustable double roller timing set. The cam sprocket comes with a Torrington bearing to reduce friction, and requires the OEM cam retainer plate to be countersunk for the provided screws. We installed the cam straight up to start, and after degreeing the camshaft, all the timing points were verified. We did this both to ensure the cam was dialed in properly (trust, but verify the “dot-to-dot” installation), but also to make sure we did, in fact, have the Cobra camshaft. (We do.)
With that, our short-block is mostly complete, save for final installation of the oil pan, the timing cover, and our Fluidampr balancer. Stay tuned as we tackle the rest of the valvetrain and the top end of the engine in the next installment of the Retro 5.0 initial build.