Aftermarket Mopar Hemi Engine That Looks Stock - Heavy Breathing Hemi

Does this look like a 484ci... 

   

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Does this look like a 484ci Hemi? That's the idea. It's what's on the inside that counts. A 12.8:1 compression, a Cam Motion solid-roller camshaft, a 4.15-inch stroke, and other goodies make this Challenger a serious Camaro stomper.

For some, muscle-era Mopars are to be revered and protected, while others feel that modifying what the factory gave us is where it's at. There's even another segment of enthusiasts that feels the car should look as close to stock as possible, yet be able to rip the rearend out from under itself while doing a holeshot. The latter group is made up of the guys who show up at a-dare we say street race-looking to sucker some poor unsuspecting sap into losing his hard-earned money with the following: "What are you afraid of? Look, it's stock."

For those in the latter group, we may just have your recipe. Dave Dudek of Shelby Township, Michigan, revealed some of the tips and tricks of making his stock-looking Hemi give the power to rip off some low 11-second timeslips. If you think because it's a Hemi a basic rebuild will suffice, think again. There are a lot of things that need to be done inside the engine, and you can do some of the tricks we'll show.

The short-block was taken to Automotive Machine in Fraser, Michigan, to have the necessary machining done. Things like parallel and zero decking may not be required for a basic rebuild, but when you need to get every last bit of power from your engine with the parts you have, these things are the norm.

If you're planning to make a serious amount of horsepower, you'll need to ensure the engine can breathe. The Hemi has long been known for its breathing capabilities. Modern Cylinder Head in Clinton Township, Michigan, got the nod for prepping the big units. Early in the process, it was noticed that some work had already been performed on the heads, which at the time may have been deemed adequate. But, it was indeed hampering the flow characteristics. In other words, the Hemi breathed in nicely but didn't exhale as well. The intake ports were fine, but the exhaust ports had been machined for larger valve seats. This modification resulted in a less than optimal venturi effect. The head could have been welded, but as thin as the material was in that area on these heads, the heat from welding could have caused severe cracks in the head. A cracked head means replacement, and replacement of a Hemi head is not an inexpensive endeavor.

The old adage still holds true-how quick you go is directly proportional to how much you spend.

To begin, you need a good...        read full caption To begin, you need a good foundation. A 4.15-inch crankshaft from Mopar Performance (PN P5007250) is checked, balanced, and knife-edged. Automotive Machine then coats it with an oil-shedding film. The film is also a thermal dispersant to help remove heat from the crank, and it also helps to cut down on parasitic losses.	When choosing pistons, the...        read full caption When choosing pistons, the final compression ratio is a big factor. These custom pistons from Diamond Racing are made to use a .990 wristpin, and internal milling is performed to lighten things as much as possible. The rods are Eagle H-beams (PN CRS680C3D). The entire rotating assembly is balanced to within .02 gram.	Crankshaft thrust (endplay)...        read full caption Crankshaft thrust (endplay) needs to be checked. The crankshaft is separated from the bearing material by only a thin layer of oil. Since the crank "floats" in the bearing, it inevitably shifts from front to back. This travel must be kept to a minimum. Here, the endplay is checked with the pistons in place. Endplay measures in at .005. Likewise, the rods must have a small amount of space to allow movement. The rod clearances are set at .0025.
The vintage '68 block is opened...        read full caption The vintage '68 block is opened up .060, and deck surfaces are checked for flatness. The block has been previously surfaced and now has a zero deck height. Here, the crankshaft is in place, and the main caps are given a final torque check.	The custom-ground Cam Motion...        read full caption The custom-ground Cam Motion camshaft has .594/.579 inch lift and .246/.252 degrees duration at .050. This is a solid roller camshaft. Any performance engine must have the camshaft degreed in to achieve optimum performance. Crower roller lifters (PN 66232) are used, along with a Rollmaster timing chain with a Torrington bearing keeping things in time.	The Mopar windage tray (PN...        read full caption The Mopar windage tray (PN P5007347) and a new stock oil-pump pickup tube are installed, and the distance between the pickup screen and the bottom of the oil pan is checked. A piece of clay is placed on the pickup, and the oil pan is put in place. Measuring how thick the clay is after being compressed by the oil pan gives you the distance. We end up with just under 11/44 inch and button the bottom end up with a stock replacement oil pan from Mancini Racing (PN MRE884K).
The heads are stock pieces,...        read full caption The heads are stock pieces, casting No. 2780559. Jeff Kobylski at Modern Cylinder Head in Clinton, Michigan, gives them a mild porting. Previously, somebody added hardened valve seats that were too large and compromised the exhaust flow. This could have been corrected with some creative welding in the port, but cracking was a possibility we had to consider. (See chart on p. 59 for flow numbers)	Some of the details on the...        read full caption Some of the details on the top side of the head include Dick Landy rockers and shaft collars, Milodon tube seal inserts, and MP rocker stands.	Cometic three-piece head gaskets...        read full caption Cometic three-piece head gaskets (PN C5455) are used to seal the head to the block. These are the best head gaskets Dave has found for use on a Hemi. Final compression thickness is .040. A nice feature of Cometic gaskets is they can tailor the thickness of the gasket. If you need to lower your compression a little, simply have them make a thicker gasket.
Piston-to-head clearances...        read full caption Piston-to-head clearances should always be checked to keep from destroying something when you fire it up. If the clearances are too close, the pistons can contact a valve, and something will give. Piston-to-head clearance on our Hemi is .050 without the gasket, and piston-to-valve clearance is .230 on the intake and .125 on the exhaust. We have more than enough.		A trick of Dave's is to coat...        read full caption A trick of Dave's is to coat the side of the intake gasket that contacts the head with 3M adhesive. This allows the gasket, when properly positioned and stuck, to be trimmed in the port area to remove any small restrictions.
	The Cam Motion cam has a tight...        read full caption The Cam Motion cam has a tight valve lash and is set at .010. Pushrods in a custom length were needed, so Straightline Performance made these nice chrome-moly pieces for us.	The factory supplied a windage...        read full caption The factory supplied a windage tray that is fastened underneath the Hemi intake. Because it helps keep hot oil off the intake, it is reinstalled.
	After the intake is buttoned...        read full caption After the intake is buttoned up, it's time to prime.	An aluminum water-pump housing...        read full caption An aluminum water-pump housing is lighter than a stock cast piece, but in Stock Appearing racing, it needs to look completely stock. A few modifications are needed. (A) The temperature-sending unit hole is plugged because it is in a different location than those in vintage '70 units. (B) A hole is then drilled and tapped in a location replicating the stock '70 location for the temperature-sending unit. (C) The MP aluminum housing also has an extra boss for alternator mounting, which must be removed.
The original Hemi intake may...        read full caption The original Hemi intake may look stock from the outside, but inside, there is mild port work, and the divider wall is cut down. Also, a small dam is built between the four- and six-cylinder ports to help with fuel distribution.	Once painted, it takes a trained...        read full caption Once painted, it takes a trained eye to find any discrepancies.	After we bolt on the accessory...        read full caption After we bolt on the accessory pieces-valve covers, viscous fan, extrude-honed exhaust manifolds, carbs, and distributor-she looks bone stock. We plan to bring all the dyno and track testing numbers next month.