As a foundation for the rotating assembly of this engine, a forged crankshaft from Callies' Compstar line was utilized with the required stroke of 4.050 inches. This cranksahft is manufactured from 4340 steel, features standard small 2.200 inch (commonly known as small-block Chevy rod journal size) journals, and has gun-drilled main journals to save weight. The Compstar crankshaft is also double keyed, and comes with a forged steel reluctor wheel to replace the brittle factory wheel for the crankshaft trigger. Compstar 6.125-inch length forged H-beam connecting rods were combined with Diamond forged flat-top pistons to give us the pump-gas friendly 10.85:1 compression we were shooting for. The Diamond pistons are lightweight, utilize a .927 inch diameter piston pin, and metric rings for reduced internal friction.
06 The new Hemi engine has many advantages, including narrower, metric piston rings for re
Camshaft selection in an engine like this is critical, and we chose to stay with a hydraulic roller since the late-model Hemi comes standard with this type of cam. We had a good idea of the cam we wanted for this engine, and calling Comp's helpline verified we were on the right track. Knowing late-model Hemis like a wide lobe separation angle, we chose a hydraulic roller cam with a lobe separation of 114 degrees. This cam features .584-inch intake and .579-inch exhaust lift, and 242 and 248 degrees duration at .050 inch lift respectively. This cam, along with a set of factory hydraulic roller lifters, will give our engine plenty of midrange torque and high end power, and should provide peak power at or just below 7,000 rpm. Since the camshaft is oiled last in the late-model Hemi, plenty of cam lube is required when assembling one of these engines.
To drive the camshaft, we chose a Manley double-roller, adjustable timing set. Unlike conventional Mopar V-8 engines, the timing marks on the late-model Hemi line up at the top of the cam gear, and the bottom of the crank gear, for proper cam timing. Additionally, the oil pump is driven by the crankshaft, so when using the wider double-roller timing set, special oil pump spacers are required and provided with the Manley timing set. We verified cam timing with a degree wheel, and utilized the provisions on the Manley timing set to make necessary adjustments before installing our Melling oil pump.
07 We chose a Comp hydraulic roller for our engine, with .584 intake lift and .579 exhaust
08 Manley makes a great adjustable double-roller timing chain and gears for the late-model
09 We chose a Melling oil pump for our 426 Hemi, which allows us to adjust oil pressure wi
10 The late-model Hemi differs from other Mopar high-performance engines in several ways,
11 Milodon offers an excellent oil system for the late-model Hemi, designed specifically f
12 The stock 6.1 Hemi balancer isn’t up to hardcore racing, so we picked an ATI unit, whic
Late-model Hemi engine oiling is critical, especially since the engine oils the valvetrain first, and then the bottom end. To provide the necessary lubrication to this engine, we called on Milodon since they have a race specific oil system for the late-model Hemi. Designed around the Challenger Drag Pak Stock Eliminator platform, the Milodon oiling system utilizes a rear sump oil pan and pickup, along with a windage tray that doubles as a crank scraper for great oil control. The late-model Hemi already has one of the best oil return designs of any Chrysler engine, and combined with the Milodon components proper oiling and scavenging of oil will be ensured.
13 This month we showed you what it takes to build a stout 426 cubic inch late-model short
Having assembled plenty of high-performance Mopar engines over the years, this author was fortunate for the opportunity to build this late-model race Hemi with the guidance of Indy's top engine builder, Ken Lazzeri. While the late-model Hemi is similar in many ways to early Mopar engines, there are a number of variances that make assembly different from earlier Mopar engines. The main bearing notches are opposite from each other rather than on the same side, which is the way BMW and Mercedes engines are and tells you a bit about the heritage of the late-model Hemi. The thrust bearing is also a separate piece, not attached to the main bearing, and is only one half circumference of the thrust provision of the crankshaft. The timing gears and chain system are different as well, utilizing a tensioner to keep the chain engaged on the gears properly. The late-model Hemi also requires thinner oil viscosity due to the lifter, pump, and oil pressure relief valve design.
We've learned a lot building the short-block for our 426-inch late-model race engine, and can tell you firsthand that you'll be surprised at the power numbers this engine makes. Next month we'll discuss the cylinder heads, induction, and ignition system of this Hemi, and show you the results we achieved on Indy's engine dyno. You won't want to miss part two of this build, and be sure to visit moparmuscle.com to see video footage of this powerful Hemi running on the dyno.
|Indy 426 ci late-model Hemi short-block
|Comp Hydraulic Roller Camshaft
|ARP Main Stud upgrade
|Melling Oil Pump
|Rear Sump Oil Pan
|ATI Balancer (SFI approved)