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Established Member
Oct 18, 2011
Lakeland, FL

Big Package
Inside Ford Performance’s big-bore, modular crate engine
By Steve Turner
Photos courtesy of Ford Performance Parts

Recently we shared Ford Performance Parts’ announcement that the OE hot rodding division is now offering a 5.3-liter modular short-block (PN M-6009-B53; $6,800). This part attracted a lot of attention from those looking for project-car propulsion or an engine refresh for a high-mileage modular. Since it resonated so, we decided to learn a bit more about this engine.

To do so, we went right to the source and contacted Ford Performance Engine Engineer Tom Dettloff about his creation, which is based on the rugged Boss 5.0 block (PN M-6009-B53; $6,800). This block actually makes the big-bore engine possible, but it was actually employed out of necessity.

“It was getting harder and harder to get ahead of the game and keep the pipeline loaded with reclaimed blocks. So, we looked back into our catalog and the Boss 5.0 was just sitting there, so while it is an iron block and you give up a weight penalty, it is also a considerably stronger block due to the mechanical properties of iron versus aluminum,” Tom said. “A lot of these combinations tend to see supercharger applications, which certainly means you are heading in the right direction by heading down the road with an iron block.”

Because of the bore size allowed by the robust Boss block Ford Performance was able to quickly develop this 323-cube engine using a proven combination of reciprocating parts.

“It has a 94mm bore and it’s a Siamese bore as well, so it’s got some strength across the deck surface… That’s the primary reason we’ve been able to go out to 94mm on the bore diameter. That’s the big advantage to the block. We stroked it, so it’s got a 3.750 stroke in it and that got our displacement up to 5.3 liters,” Tom said. “It was as good as we could make it quickly. The 3.750 stroke has been out there for a while. It’s proven combination and there are good rods and pistons to go with it. That allows us to put in the premium components.”

Because of its parts, this engine has proven quite durable in Ford Performance’s stringent testing. For most applications, this short-block is going to offer plenty of durability.

“…Basically we ran that durability test under some pretty abusive conditions, both temperature-wise and load-wise. A typical durability test for us will run several minutes of an hour straight,” he said. “It’s not even anything you could accomplish unless you were in a boat… It allows us to see if there are any design flaws or any material issues that we run into via compatibility of bearings with the crankshaft, piston loading and things of that nature.”

“That engine was durability tested for, I believe 30 hours…” Tom added. “Something like that wouldn’t even be achievable. If you found a flat piece of ground to run on (for that long) you would at least have to slow down to put more gas in the tank.”

So the engine offers more displacement and greater durability in a really flexible package. That’s because the engine’s Mahle piston design features valve reliefs designed to work with Two-, Three- or Four-Valve cylinder heads. Ford Performance even tested this engine with larger camshafts and cylinder heads from the aftermarket.

“You can certainly find yourself with camshafts out there where you are gonna have to notch the piston,” Tom cautioned. “Obviously we recommend that everybody check the piston-to-valve clearance at overlap so that you don’t get yourself into trouble there.”

You’ll also want to sneak up on the tuning if you are building a power-adder combination around this 5.3-liter short-block.

“One thing you have to be cognizant of is with that much added displacement the compression ratios go up pretty significantly over what would be a stock 4.6,” he cautioned. “A larger combustion chamber or a ported chamber will bring down the CR so it’s a little easier to put on a supercharger, plus it will help unshroud the valves and improve the airflow a little bit.”

So there you have it. If you were considering this short-block for your project, you can rest assured that Ford Performance constructed this engine with good parts and made sure it was up to the task for your performance application.


If you are in need of a new modular engine for your project car, Ford Performance offers this 5.3-liter short-block based on its rugged Boss 5.0 block. It is a direct replacement for a Two-, Three- or Four-Valve 4.6, but depending on front cover you use, you may need to seal off one of the bolt holes.


At the heart of this big-bore modular is Eagle’s forged crankshaft. It features 3.75-inch stroke and an eight-bolt flywheel pattern.


Ford Performance also turned to Eagle for a set of rugged H-beam rods for this engine. The rods measure 5.85 inches and are fastened with ARP 2000 bolts.


The parts that make this short-block so flexible are these forged-aluminum Mahle slugs featuring a dish designed to work with Two-, Three- and Four-Valve cylinder heads.


Established Member
Oct 27, 2014
Anybody running one of these N/A, super high compression, race gas or e85, crazy cams, and 7000-8000 rpm? 2 or 4 valve. Thinking about this as a road race engine. I am a little sceptical of the eagle parts.

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