You may or may not know all of the details about Chrysler's latest version of the Hemi engine, but one thing is certain: This engine is a performance powerhouse. Even in stock form, the late-model 5.7, 6.1, 392, and 6.4 Hemi engines will run circles around past versions of this venerable powerplant in terms of power and efficiency, and the new Hemi platform responds great to modifications as well. So when it came time to choose an engine platform for the '10 Dodge Challenger we're building as a dedicated drag racing car, the late-model Hemi just made the best sense. This month we'll show you what parts we utilized to build our 426-inch short-block, and next month we'll finish the build with a full description of the top end and dyno testing. If you're a fan of the new Hemi, then you'll definitely want to follow this build as our results were impressive. And if you're not a fan, well this pump-gas late-model Hemi may just convince you that you should be.
01 With all five cross-bolted main caps and a great oiling system, the 6.1 liter Hemi bloc
02 We won’t be utilizing the Multi-displacement system (MDS) so the provisions in the vall
If you compare the late-model Chrysler Hemi (or third generation Hemi) to the first Hemi engines or even the famous second-generation 426 Hemi built during the '60s and '70s, the newest version wins in every category. No matter if comparing power per cubic inch, average power, peak torque and horsepower, efficiency, or weight, the newest Hemi engines simply outperform all of the past versions hands down. Another advantage to the third generation Hemi engine is that contrary to the somewhat rare first and second generation Elephants, these engines are plentiful and inexpensive.
03 The factory installed camshaft bearings in the late-model Hemi are two-piece units, and
Unlike the second generation Hemi which was a rarely-selected optional engine only available in select models, late-model versions are widely produced and served as the base V-8 engine in hundreds of thousands of cars and trucks produced by the Chrysler Corporation during the past decade. So with more and more of these cars accumulating high mileage and succumbing to accidents, finding a late-model Hemi in the local scrap yard or from a core supplier is a fairly easy and inexpensive proposition. In fact, we know of several enthusiasts who have purchased running 5.7 liter Hemis locally here in Florida for less than a thousand bucks. Bare blocks, cranks, cylinder heads, and other parts are also available directly from any Chrysler or Dodge parts dealer, so if you don't want to bother with a used engine you still have the option of building one with new parts.
Even better, aftermarket companies like Indy Cylinder Head, Comp Cams, Callies Crankshafts, Milodon, and many others already support the late-model Hemi with a great variety of aftermarket parts to make these engines really perform. Since our latest project car is a '10 Challenger that will be dedicated to bracket racing, we decided a third generation Hemi engine made perfect sense to power our car. And with current pump gas prices approaching what we paid for racing fuel in the not-so-distant past, we made the decision that this engine would have to run on pump gasoline with an octane rating of 93. With these factors in mind, we assimilated a list of parts that would result in a powerful 426 cubic inch late-model Hemi, which we could fuel up at the local gas station.
04 Compstar (Callies) makes a great forged crankshaft, with a stroke of 4.050 inches. Ours
The first step in our process was to choose the appropriate parts for the short-block of this engine. Our choices were limited to the 5.7 and 6.1 blocks due to availability, and the differences in these blocks are minor but significant. The 5.7 Hemi utilizes a 3.920-inch bore size combined with a 3.58-inch stroke, while the 6.1 Hemi's bore size is 4.060 inches with the same 3.58-inch stroke. Since the 6.1 block has larger diameter bores, as well as reinforced bulkheads, we chose this block as the foundation for our late-model 426.
All late-model Hemi blocks are hybrids of sorts, using both standard and metric hardware in various locations. For this reason, it really helps to have a core engine around when considering a build like this. Since we built our engine at the Indy Cylinder Head facility in Indianapolis, Indiana, we had the luxury of their supply of hardware and parts. If you're going to build a new Hemi in your garage or have your local machinist perform the work, be sure to not throw out any of the hardware, fittings, or pipe plugs as they might be difficult to replace at the local hardware store. For our build, we utilized a new 6.1 block, and Indy's full service machine shop prepped the block for our stroker application.
05 The rear main seal of a late-model Hemi is a one-piece Teflon seal. Unlike older Mopar
To achieve a displacement of 426-inches (or 425.67928 to be exact), we utilized a bore size of 4.090 inches and a stroke of 4.050 inches. The 6.1 block can be bored to this dimension with plenty of cylinder wall left, and to fit our stroke we only needed to cut small provisions for the connecting rods at the bottom of the cylinders. Other block modifications include chamfering the inside of the provision for the oil filter, blocking off the MDS provisions, and installing one-piece grooved camshaft bearings to replace the factory two-piece units.