Break-in For 5.7 Hemi -
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Unread 11-28-2007, 04:45 PM   #1
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Break-in For 5.7 Hemi

jeep says drive moderatly for 300 miles . any advice ?

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Unread 11-28-2007, 07:20 PM   #2
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This means run it through the RPM range of the motor. Every once in a while floor it from a good rolling start and let it max in the gear and shift. It lets the valves and rings all seat to each other.
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Unread 11-29-2007, 01:36 AM   #3
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Just press both the gas and the brake pedal all the way at the same time. It's good for it.

Not really.

I think it will break in just fine no matter how you drive it.

I had an 04 GMC 2500 HD with the 8.1 gas engine and Allison tranny. I broke it in by pulling a 12000 lb boat. I picked up the truck, drove it to where my boat was stored and started towing with 6 miles on the truck. Many thousands later not a single problem.

I think modern engines will do fine no matter how you drive them.
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Unread 11-29-2007, 06:30 AM   #4
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just follow the instructions in the owner manual you will be fine, these modern engines break-in easily and with a great deal of forgiveness in the process.
2008 Grand Cherokee Limited 4X4, Light Greystone Pearlcoat, Hemi, Tow Group, 18" Chrome Clad Wheels. Original owner, 20,000 miles

2002 Wrangler Sahara, black, 4.0L, 5-speed, Dana 44 rear axle with Trac Loc LSD, duel tan tops, Canyon wheels with Wrangler Silent Armors. 75,000 miles, 2nd owner.
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Unread 12-04-2007, 11:25 AM   #5
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not sure what jeep does but....

at the bmw factory in the US, they run the cars directly after they are completed on the assembly line. at the end of the assembly line is a dyno room and they run the bmw's at 120 mph for a period of time in there. and that is all with 0 miles on them.

i am sure they let them warm up first - so by the time they start the high speed run the car prob has 1 or 2 miles on it.

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