Ford Racing has been an innovator in developing aftermarket engine systems that allow engine builders express their creativity. Their 5.3L Mod Motor crate short-block is one of their best. This short-block is terrific in "as delivered" form allowing builders to simply strap on cylinder heads, camshafts and fuel injection and head down the road. But for those looking to develop something special, this short-block is up for whatever you can throw its way.
With the mindset that we wanted to still be able to run pump gas where possible, we decided to install lower compression pistons to replace the original 10:1 compression Mahle pistons that come with this engine. That's not because there is a problem with the Ford-installed Mahle pistons - not hardly. But we knew that with a 10:1 compression engine, we would have to add additional measures to protect against detonation such as an intercooler or backing off the timing; the latter of which would also greatly decrease our power output. By lowering the compression, we could still run on pump gas (dependent on how much boost we added) and ultimately achieve more power than we could by supercharging a 10:1 engine.
Using a custom set of Mahle lower compression pistons (and Mahle Chrome Moly piston rings), Trick Flow Specialties aluminum cylinder heads (PN TFS-51910001, which feature a 38cc combustion chamber) and our Fel-Pro MLS head gaskets (crush to 0.040-inch), our new static compression ratio would end up at exactly 9.06:1. That's about right for our planned supercharger upgrade. Best of all we still retained the high quality Ford Racing and Eagle Performance components to ensure durability.
A Note About TFS Cylinder Heads
TFS has been in the engine component business for several decades now and knows a ton about Ford engines from years of testing, tuning and general engine experimentation. Their newest "Twisted Wedge" cylinder heads for both the Romeo and Windsor 2V engines are a "total departure" from standard. TFS redesigned the head by moving the combustion chambers and intake valves to the opposite side of the camshaft (opposite to the factory orientation). According to TFS, this change results in a major improvement in mid-lift airflow as well as piston-to-valve and piston-to-bore clearance. Equipped with a single beehive-type valve springs and Chrome Moly spring retainers, these represent a great bolt-on-and-go option for "mildly modified engine" applications.
The above noted benefits really come into play when using higher lift camshafts and oversized valves to generate higher horsepower and torque. Other cylinder head design benefits include a 3/4-inch deck surface to provide better head-to-block sealing and high flow near CNC-level intake and exhaust runners with CNC-profile combustion chambers.
To be totally clear, the only parts that we changed from the way Ford Racing delivered our 5.3L short-block were the pistons, piston rings and bearings - the rest of the engine remained intact. That's how much we like this engine, a fact that should be clear by now. Of course, our total engine assembly was rebalanced, because of the new pistons, by QMP Racing Engines, our go-to company for these critical engine prep operations.
We disassembled the 5.3L Ford Mod-Motor and carefully checked everything for proper clearances and condition. Not surprisingly, everything was exactly as ordered. A comparison of the Ford-installed Mahle pistons and the new custom-made set of Mahle pistons that would replace them revealed several obvious differences, most notably in the height of the wrist pins.
On the higher compression Mahle pistons, the wrist pin was lower in the piston body when measured from the piston dome. For this reason, and the slightly different design of the dome, final compression dropped about on point as noted earlier moving the piston about 0.015-inch lower in the cylinder bore as well.
If you haven't assembled a Mod Motor, you've missed out a super strong engine upgrade when compared to classic Ford Windsor and Cleveland engines. It should be noted that our 5.3L engine is not the much-lauded "Cobra block" so loved by racers that features the four-bolt main system. Our engine had two bolts to hold the main cap in from the bottom of the block and also two side bolts that further reinforce the crank placement (another benefit for our power-adder directive).
While classic engine designs feature main caps that simply drop in place, the Mod Motor design requires you to line up each main cap and tap them down into the block with a dead blow hammer before bolting in place. To further bulletproof the bottom-end, we used ARP Bolts and torqued them in place as per Ford Racing specs.
Follow along as we prep our Ford Racing engine for supercharging. Along the way we will show you some of the techniques we used to build our Mod Motor, courtesy of the fine folks at Gear Driven Automotive. Hosted by owner Saul Gutierrez, we carefully assembled an engine that was more than ready for its future performance tasks.
Ford Racing 5.3L Short-Block Crate Engine Highlights
-Engine type: 4.6L based Modular short-block
-Displacement (Liters/cu in): 5.3L/323 cubic inches
-Bore x stroke (in): 3.701 bore x 3.750 stroke
-Block: Ford Performance M-6010-BOSS50 Cast Iron performance block
-Crankshaft: Eagle 3.750-inch stroke forged steel crankshaft with 8 bolt flywheel pattern
-Connecting Rods: Eagle 5.850-inch forged steel H-beam rods with ARP 2000 bolts
-Pistons: Mahle forged aluminum pistons
-New high pressure oil pump
-Neutral balance rotating assembly
-Designed for 2, 3 or 4 valve cylinder head combinations (piston-to-valve check required depending on camshaft)
-Assembled and ready for your heads, cam, and timing set
Trick Flow Specialties
Twisted Wedge 185 Cylinder Heads TFS-51910001
Intake Gasket set TFS-518-0002
Mahle Pistons (custom) 197854000 26211
Mahle piston ring set 9400MD - 12
1.2mm - Cast iron
1.2mm - Cast iron
2.5mm - twin scrapers and oil ring
ARP side bolts - M8
Eagle Rod - ARP 2000 - 43 ft-lb
Center Bolt Main caps - 60 ft-lb
Side Main M8 Bolts - 45 ft-lb
The Ford Racing 5.3L Mod Motor short block is one of the best values around for Ford fans looking for a turn key building block for big power. The engine features Mahle pistons and rings and Eagle H-Beam connecting rods with a forged crankshaft.
This plate documents that our block as an official Ford Racing block. Along with the part number and date of manufacture, it also denotes the serial number for the block for further validation.
This Boss block features a super strong main web with two-bolt main caps and further strengthened by the use of side bolts that pin the caps in place through the sidewalls of the block.
As you can tell from this angle, the cast iron engine is thick in all the right places. The oil pump is a "gerotor-driven" unit that bolts to the face of the block using the supplied bolts.
This is the essence of our upgrade; the Mahle pistons supplied in the Ford Racing short-block (left) and the custom pistons we had built by Mahle for our supercharged application (with connecting rod). While they both may appear to have a similar concave dome piston design, there is a difference in their final static compression ratios when installed - 10:1 vs. 9.06:1.
Here's where the difference between the two pistons is most obvious. The wrist pin height in the lower compression piston on the right moves the piston down in the bore 0.015-inch. In a careful review of the piston construction, the reliefs in the side of the piston below the wrist pin hole and the distance between the ring lands and dome of the piston all translate into an altering of the total static compression of our engine. Displacement with the new pistons dropped only slightly, the new engine size: 5290cc or 322.74 cubic inches. Let's just call it a 5.3L!
Prepped and ready for their turn to go into our engine, the original Eagle H-Beam connecting rods that came with our Ford Racing engine have been fitted to our new lower compression pistons. As is standard practice with an engine that has changed any major reciprocating component (pistons, in our case), the engine was rebalanced to ensure proper operation and overall durability.
For those not familiar with the inner workings of a Mod Motor, the bearing caps and main saddles use bearings of a slightly different design. For the 1 and 5 bearings, a standard bearing is seated in the saddle and these side thrust plates are separately placed in the side reliefs of the cap and saddle. The lubricant applied to the bearing helps keep these thrust faces in place.
As was the case with the bearing cap, this is an example of the bearing thrust surface as installed into a main bearing saddle.
This shows the difference between the bearing caps used in this engine. As you can see, two of the main caps use standard bearing inserts and other require the thrust bearings that fit in the recesses noted on the cap and main saddles.
Our Eagle forged steel crankshaft is stout and features a stroke of 3.750-inch, which equates to a total displacement of 5.3-L with our piston and rods. We wiped it clean with a soft towel before lubricating the journal surfaces for installation.
We lowered the crankshaft in place and reviewed the positioning. As noted earlier, the crankshaft had been rebalanced due to the change in pistons.
The folks at QMP Racing Engines in Chatsworth, CA balanced our engine adding material in some areas while removing it in others; both are visible in this image.
The crankshaft fits down in the block and should rotate freely in this position. The caps will be bolted in through the sides of the block and the two-bolt main arrangement.
Balanced to a tenth of a gram, QMP Racing Engines is well versed in high quality engine part prep. The parts are balanced individually and as partial assemblies as shown here.
The main caps are interference fit as opposed to classic Ford builds, where the caps just drop in place. The cap must be lined up exactly side-to-side or it will not go into place.
After it is aligned with the side rails, tap the cap down till it meets the bearing saddle. Use a dead blow hammer rather than any form of steel hammer, which might damage the cap.
To get the bolts to thread can require some tapping of the cap forward and back within the block to get the bolts started. The bolts should be started by hand and then use a wrench to snug them down.
After the main bolts are in place, chances are the side bolts will not line up. More adjustment is required to get the bolts to thread in place.
This crankshaft features an 8-bolt pattern and will require the appropriate flywheel or flexplate for final installation.
The rear main cap features the bearings with the side thrust bearing surfaces. Regardless of this fact, all of the bearing caps, they will have to be tapped in place with the dead blow hammer.
ARP bolts are without peer in the performance engine building world. We used ARP bolts not only for our main caps and side bolts but also in the Eagle connecting rod ends.
With the crankshaft torqued in place to 75 ft-lb, we checked endplay with a dial indicator. Endplay for our crank was with spec at 0.0085-inch.
The Ford Racing windage tray attaches to the ends of the main cap bolts. It fits down into the block and improves crankshaft oiling by reducing internal turbulence. We did a test fit at this point to make sure it would fit properly when the engine was assembled.
Our original Mahle piston rings were installed first, the upper and lower scrapers snapped in place on either side of the oil ring.
To check end gap on our compression rings, we first placed the ring in the bore and made sure it was evenly inserted in the bore from the top of the cylinder.
We then used a feeler gauge to check the end gap of the piston ring in the bore. Make sure that the feeler gauge is held as close to 90-degrees to the cylinder direction as possible to get an accurate reading.
The block cylinder surface itself was finished by Ford Racing to achieve compatibility with the Mahle Plasma Moly piston rings.
Using the Mahle piston ring calculation (to determine end gap allowance) of 0.004 times a bore of 3.700-inches we came up with 0.0148-inch. Our feeler gauge measured the current end gap at 0.0150-inch so we were within spec and no ring grinding was necessary.
We installed the top and second piston rings and made sure to keep the ring gaps as far apart as possible. If they line up, the engine could have excessive blowby.
These alignment rods protect the rod from coming in contact with the crankshaft journals during installation.
Loctite thread locker is important to use on key bolts like the main cap bolts and side bolts.
We compressed the piston rings and aligned the skirts into the cylinder bore before tapping in place with the handle of a wooden hammer.
We installed the bearings and rod end caps and torqued them in place. We torqued them to 43 ft-lb each.
With all of the pistons in place and having rechecked our torque specs several times, we turned to the gerotor-style oil pump. This pump fits to the front of the block and is driven by a concentric on the crankshaft. This demonstrates the perfect positioning of the oil pump. For the record, it took us several attempts before the pump was flush against the block face and fully engaged with the crank. With the short-block complete, we'll focus on the top-end next.
Photography by Cam Benty