Heart of the ‘90s — Retro 5.0’s Short-Block Comes Together

Heart of the ‘90s — Retro 5.0’s Short-Block Comes Together

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.

Here you can see one of the most important upgrades we made in the shortblock assembly: modern Clevite bearings. You can see the cam bearings we knocked out of the block below the brand spanking new Clevites. The rod and main bearings are both coated H-series performance pieces, that should handle all of our dyno time well.

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.

The Total Seal crosshatch angle gauge makes getting the exact angle easy. If it's too shallow, speed up your stroke rate. If it too high, slow down your stroke rate. The 320-grit ball hone left us with a way better finish than we thought we'd have from only a ball hone.

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.

The ICON forged 2618 pistons require a little extra piston-to-wall clearance to account for thermal expansion, and we were dead on with that, with off-the-shelf standard-bore pistons. The kit comes with tool-steel wrist pins and spirolock pin locks. This combo should stand up well to our future forced induction goals, along with providing some added compression N/A, thanks to the flat-top design.

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.

Here, you can see the top (left) and second (right) piston rings. The little notch in the corner of the ring controls the amount and direction of the twist. The top is a ductile-iron, plasma-moly "positive twist" design, and the second ring is a cast-iron "reverse twist" design.

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).

We used the ProForm electric ring filer to gap the ring provided in the UEM kit. The instructions called for a street N/A gap factor of .004 inch per inch of bore, and .005 for a street forced-induction application. We decided that it would be best to go with the larger gap out of the gate, so that we don't have to address the ring gap in the middle of testing. Following the current thought process, we added an additional .002 of gap to the second ring, resulting in final measurements of .020 inch for the top ring, and .022 for the second ring.

Bracing Ourselves

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.

Here you can see the Moroso main girdle. It sandwiches between the main cap and the supplied ARP 8670 main bolts, with cutouts over the main caps so that it rests squarely on the bolt bosses and not the middle of the cap. As you can see from the markings on the bolt, we torqued the mains in three stages.

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.

Even with all of the measurements from Melling and Moroso ahead of time looking solid, there was a slight bit of interference between one of the main bolts and part of the oil pump casting. A little careful massaging with a mini file, and we got clearance around the bolt head.

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.

On the left, you can see how perfectly the Moroso pickup fits both the Melling 10687 oil pump and the main girdle. On the right is an OEM pickup from Melling laid on top to show the difference in tube geometry required to clear the girdle.

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.

This is a cam card we’ve recreated with Ford’s data for the F3ZE-6250-CA camshaft in a Cobra application. Since we’re starting out with an E7 head combo and stock 1.60:1 rockers, we’ll have slightly less lift at the valve. Also note, the event timing numbers are at .050-inch.

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.

The Melling billet 9-way adjustable timing set offers up to 8 degrees of advance and 4 degrees of retard, but we installed it straight up, initially. We used the ProForm cam-degree tools we highlighted in a previous article, along with a homebrew timing pointer, to degree the cam and check all the valve events.

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About the author

Greg Acosta

Greg has spent seventeen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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