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Building “The Elephant”

426 awesome cubic inches of Hemi for a ’69 Cuda

Jeff Huneycutt - June 21, 2012 10:00 AM

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KT Engine Development plans to keep the engine old school with mostly stock components, but will make a few concessions to modern technology for better reliability. One such change includes getting rid of the original O-rings around the chambers in favor of the better sealing, modern MLS head gasket from Cometic.

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Here’s the deep-skirted block after it has been fully machined, painted and prepared for assembly. There’s no doubt this casting was engineered to withstand big power. Notice the bolts that will be used to tie the main caps into the block skirt laterally for extra rigidity.

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Along with a piston throw of 3.75 inches, the original crank features 2.750-inch main journals along with 2.374-inch rod journals. It is definitely no lightweight, but more than 40 years after it was first manufactured it is still ready for service.

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The crank is secured in the block with the main cap bolts torqued up to 100 lbs-ft and the side bolts spun down to 45 lbs-ft.

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The rest of the rotating assembly is a set of stock length 6.680-inch Eagle H-beam rods and 0.050-inch-over Diamond pistons.

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To keep the compression up with the large Hemi combustion chamber, the piston requires an 84.8cc dome. Because of the tall dome the compression height (the distance between the center of the pin and the top of the piston) is an incredible 1.965 inches. This makes for a heavy piston that requires engine builders to make power without the help of lots of rpm. 

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A hemispherical chamber with opposing intake and exhaust valves is one of the best designs when it comes to moving air through a two-valve setup, but it also comes with a few compromises. The large chamber means lots of piston dome (as you can see here), which can obstruct and slow down the flame kernel once the spark plug fires off the air/fuel mixture.

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Engine builder Ken Troutman applies lubricant before installing the solid flat tappet camshaft ground by COMP Cams. The cam specs out at just over a half-inch of valve lift with 240/242 duration.

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Cylinder head specialist Kevin Troutman (Ken’s brother) cut 0.050 of an inch off the deck of the cylinder heads to get rid of the O-ring groove. The stainless steel valves measure out at 2.250 inches for the intakes and 1.940 inches for the exhausts.

 
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To help keep those big, heavy valves under control, KT Engines settled on a set of nested valvesprings that rated at 120 pounds of pressure with the valves against the seat and 340 when they are fully open. 

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Cometic MLS (multi-layer steel) gaskets provide the seal between the chambers and the cylinder bores.

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These Hemi heads have a unique bolting system that requires a set of studs to be inserted into the heads before they are set on the block.

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The studs extend through bosses that will split the pushrods once they are installed. Because the bottoms of the bosses are so close to the lifter valley, there is no way to install the studs after the heads are on the block.

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To get the nuts properly torqued onto these upside-down studs, a crow’s foot attachment is required on the torque wrench. Make sure to use the shortest extension possible as the extra leverage these attachments provide can throw off the torque reading on your wrench.

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 Once the regular head bolts on the top side have been torqued in place, Ken Troutman turns his attention to the solid, flat tappet lifters from Crower. A good coat of assembly lube from Royal Purple will help provide protection to the lifter faces during the first few revolutions after this beast first cranks up.

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The valvetrain is stock vintage Hemi with 1.57:1 ratio rocker arms on each side. Notice the lash adjusters with hex nuts on the pushrod end of each rocker.

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We’re talking pure old school here. There are no roller tips on these rockers, but the ends are set on a radius to make the action on the valvestem tip smoother. The oil on the end of the rocker provides cooling oil to the spring. The oil is fed up from the cylinder head, into the rocker stands and to the rockers.

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The Hemi uses a unique pick-up with a ½-inch pipe thread into the block. Pick-ups for oil pans for the 440 won’t work because they use a smaller 3/8-inch pipe thread.

 
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The 426 uses this stamped windage tray that fits between the block skirt and the oil pan. Make sure you order two oil pan gaskets in order to properly sandwich the windage tray and eliminate leaks.

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The large capacity Milodon oil pan isn’t proper old school, but it still looks good and is designed to fit the ’69 Cuda chassis without any problems.

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A modern MSD distributor provides a more consistent and powerful spark than anything available when this motor first made the scene. The intake is a dual-plane Mopar piece set up to accept twin four-barrels.

 
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Two Edelbrock 650cfm four barrels handle the job of feeding this hungry beast.

 
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And it wouldn’t be a proper Hemi without the spark plug wires routing through the valve covers.

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Even though the compression was purposely kept low (around 10:1) so that the Hemi would be happy on pump gas, it still produced and incredible 516 lbs-ft of torque at 4,600 rpm and 550 horsepower at 6,400.

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When Chrysler decided to get back into the Hemi engine building business in 1964, it got back in a big way.

The largest displacement the company made when it stopped production of the first generation of Hemis in 1958 was a mere 392 cubic inches. But when Chrysler revived the Hemi engine primarily for NASCAR racing, it upped the ante to 426 cubic inches thanks to a 3.75 inch stroke and 4.25 inch cylinder bore.

That was 1964, and by 1966 you could finally buy one in a street car thanks to NASCAR’s homologation requirements. The 426 was dubbed the “Elephant” because of the large package size that resulted from the large bore and stroke along with the acreage on top of the Hemi heads required to mount the rockers.

The street Hemi was produced by Chrysler between 1966 and 1971. Officially, it produced 472 lbs-ft of torque and 425 horsepower in its dual-carb form. We spent some time with KT Engine Development as they rebuilt an Elephant that will find its way back to its natural habitat in a ’69 Cuda. This build will keep the 426 close to its roots with a stock block, heads, crankshaft and rocker setup, but a few modern touches are going to be thrown in to maximize the fun while minimizing maintenance and aggravation. And at around 10:1 compression, this big boy should run happy and cool all day long on unleaded pump gas.

For Your Information

KT Engine Development

(704) 784-2610

 

 

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