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Aftermarket Mopar Hemi Engine That Looks Stock - Heavy Breathing Hemi

Look Stock, And Go Like Stink!
September, 2003
By Randy Bolig
Photography by Dave Dudek, Automotive Machine
1968 Challenger Hemi Engine Finished
Does this look like a 484ci... 
   
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1968 Challenger Hemi Engine Finished
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.
Flow Numbers
From Superflow 600
At 28 Inches, 4.320 BSC
IN-LiftExhaustIntake
 c.f.m.c.f.m.
.10061.275.0
.200125.6158.5
.300165.8250.0
.400193.4317.4
.500212.1365.2
.550217.7375.5
.600221.7373.7
.650223.3371.9
.700225.2371.5

Mopar Performance Crankshaft
To begin, you need a good... 
   
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Mopar Performance Crankshaft
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.
Diamond Racing Pistons
When choosing pistons, the... 
   
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Diamond Racing Pistons
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.
1968 Challenger Hemi Engine Crankshaft
Crankshaft thrust (endplay)... 
   
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1968 Challenger Hemi Engine Crankshaft
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.
1968 Challenger Hemi Engine Block
The vintage '68 block is opened... 
   
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1968 Challenger Hemi Engine Block
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.
1968 Challenger Hemi Engine Cam Motion Camshaft
The custom-ground Cam Motion... 
   
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1968 Challenger Hemi Engine Cam Motion Camshaft
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.
Mopar Windage Tray
The Mopar windage tray (PN... 
   
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Mopar Windage Tray
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).
1968 Challenger Hemi Engine Head Porting
The heads are stock pieces,... 
   
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1968 Challenger Hemi Engine Head Porting
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)
1968 Challenger Hemi Engine Head Details
Some of the details on the... 
   
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1968 Challenger Hemi Engine Head Details
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 Head Gasket
Cometic three-piece head gaskets... 
   
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Cometic Head Gasket
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.
1968 Challenger Hemi Engine Piston Head Clearance
Piston-to-head clearances... 
   
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1968 Challenger Hemi Engine Piston Head Clearance
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.
Spray Paint Gasket
1968 Challenger Hemi Engine Intake Gasket Install
A trick of Dave's is to coat... 
   
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1968 Challenger Hemi Engine Intake Gasket Install
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.
1968 Challenger Hemi Engine Block
1968 Challenger Hemi Engine Cam Motion Camshaft
The Cam Motion cam has a tight... 
   
  read full caption
1968 Challenger Hemi Engine Cam Motion Camshaft
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.
1968 Challenger Hemi Engine Windage Tray
The factory supplied a windage... 
   
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1968 Challenger Hemi Engine Windage Tray
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.
1968 Challenger Hemi Engine Gasket
1968 Challenger Hemi Engine Prime Block
After the intake is buttoned... 
   
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1968 Challenger Hemi Engine Prime Block
After the intake is buttoned up, it's time to prime.
1968 Challenger Hemi Engine Water Pump
An aluminum water-pump housing... 
   
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1968 Challenger Hemi Engine Water Pump
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.
1968 Challenger Hemi Engine Intake
The original Hemi intake may... 
   
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1968 Challenger Hemi Engine Intake
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.
1968 Challenger Hemi Engine Painted
Once painted, it takes a trained... 
   
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1968 Challenger Hemi Engine Painted
Once painted, it takes a trained eye to find any discrepancies.
1968 Challenger Hemi Engine Finished Block
After we bolt on the accessory... 
   
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1968 Challenger Hemi Engine Finished Block
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.
Mopar Performance
www.moparperformance.com
Dick Landy Industries (DLI)
818/341-4143
Milodon
Simi Valley
Ca
805/577-5950

milodon.com
Automotive Machine
810/296-6501
ARP
Ventura
CA
(800) 826-3045

www.arp-bolts.com
Cam Motion camshafts
225/926-6110
Diamond Pistons
Clinton Twp.
MI
877/552-2112

diamondracing.net
Straightline Performance
Okemos
Mi
(517) 381-8801

www.straightline-perf.com
Eagle Specialty Products
Dept. SC
Southaven
MS  38671
Cometic Gaskets
Concord
OH
(800) 752-9850

www.cometic.com
Mancini Racing
P.O. Box 239, Roseville, MI 48066
orders, (800) 843-28

www.manciniracing.com

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