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Introduction & History | Feature differences | Manifold / Cams kit |
Manifold / Cams part #'s | HO Intake system | HO engine Specifications |
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The 4.7-Liter HO engine
A performance enhanced "HO" version of the popular 4.7-Liter V8 engine made its premier in the 2002 Grand Cherokee. The HO engine was a Grand Cherokee exclusive for the 2002-2004 model years, available as an option on Limited models and standard on the Overland - but not available on the Laredo. For the 2004 model year, Jeep added the HO as an option on three new special models, the Freedom Edition, Columbia Edition and the Rocky Mountain edition. The performance modifications (listed in the chart below) added 30 horsepower and 30 Ft.-Lb. of additional torque. The HO engine is designed to run perfectly on standard octane fuel, but for maximum performance Jeep recommends premium fuel. The HO engine was discontinued in the Grand Cherokee at the end of the 2004 model year. The all-new 2005 model Grand Cherokee's offered the new 3.7 V6, the standard 4.7, the 5.7 Hemi and the new 6.1L Hemi SRT engines. Starting at the end of the 2005 model year, the 4.7 HO engine became availble in the Dodge Dakota.
What no ones realizes, and being revealed here for the first time, is that the HO engine was originally planned for the 2001 model year. Several 2001 Grand Cherokee models were built with the 4.7 HO engines back in 2000! Plans for a "future" HO version of the 4.7 were put together when the new engine was original designed for the 1999 model year, back in 1996/1997. The first HO engines were assembled in the fall of 1999 and put into 2001 model pilot Grand Cherokee's in early February 2000! Twelve of these models were built, complete production versions right down to the HO badges. Colors were Stone White, Patriot Blue, Flame Red, Sienna and Champagne. These special 2001 HO models also included an exclusive "Sport suspension", different than that of the Up Country package. Components included exclusive springs (ZKN/ZKT front and ZYN/ZYT rear), Goodyear P235/65R17 BSW AS/P tires, chrome tow hooks and the skid plate package. Even more interesting is the axle ratio, which has never been used on any other Grand Cherokee model, 3.91 ! For reasons unknown, the HO engine was held back until the 2002 model year. It's possible that for marketing reasons Jeep wanted to introduce the HO with the new Overland model, and to have a key option added to the list of new features being implemented for 2002, the start of the second half of the WJ generation. New features for 2002 included side air bags, adjustable pedals, the Rain Sense wiper system and the Tire Pressure Monitor System. The HO engine was the "icing on the cake" and turned out to be a very popular and successful option. |
Summary of HO engine feature differences
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1. Block - Detonation sensor bosses in the valley | 10. Intake - low-restriction intake system (different resonator, air filter, air filter hose and housing) | |
2. Camshaft - custom profile lobes (designed for increased performance) | 11. Knock sensors - two, stereo | |
3. Connecting rods - modified, with floating wrist pins (vs pressed-fit pins in standard V8) | 12. Main bearings - tri-metal (vs bi-metal in standard V8, designed specifically for the HO engine) | |
4. Crankshaft - forged steel (vs cast iron in standard V8) | 13. PCM calibration - unique programming | |
5. Crankshaft damper - unique to H.O. | 14. Pistons - dome shaped for increased compression ratio | |
6. Cylinder heads - different shaped combustion chambers (for improved airflow). The letters "H.O." are cast on the front end of the heads. | 15. Spark plugs - platinum tipped | |
7. Exhaust tip - chrome (2002 models only, decontented for 2003 models. Available only as a one-piece assembly with muffler) | 16. Valves - unique exhaust valves (same lift as standard V8) | |
8. Fuel injectors - higher flow (+3.3 lb/hr) | 17. Valve springs - upgraded valve springs (intake & exhaust. Larger diameter wire and more coils) | |
9. Intake manifold - modified (shorter runners) |
Quite a few Dodge truck owners have successfully installed the manifold and cams into their standard 4.7 engines without any major problems. Most have reported horsepower gains from 5% to 15%, varying at different RPM's. Anyone interested in doing this upgrade or learning more about it should visit the message boards at DodgeDakotas.com and search through the HO related posts. Some Jeep owners are now considering this upgrade, we'll report on the results as info becomes available.
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Camshaft: Custom profile lobes (designed for increased performance)
Piston diameter: 92.975 mm (3.6606 in.)
Valve system: Chain-driven SOHC, 16 valves, hydraulic end-pivot roller rockers.
Unique exhaust valves
0-60 mph: 6.9 (Motor Trend)
Fuel Economy mpg (EPA est., City/Hwy): 14/19
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