New motor break in tips

Jamesmoore554

Jamesmoore554

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Sep 3, 2014
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In process of motor rebuild and was wondering best ways possible to break it in so rings seat and everything seats properly. Im still new to most of this. Thanks!
 
No prolonged idling, no constant rpm, and no heavy hauling, for the first 5000 miles or 50 hours. Use conventional oil for break in oil, no synthetic. WOT is OK for short bursts but not for extended periods. Otherwise than that drive as u normally would and enjoy.
 
In the Cummins owners manual it says tow heavy before the first 4000 miles or the motor will not get seated properly.
 
Mountainman234 said:
No prolonged idling, no constant rpm, and no heavy hauling, for the first 5000 miles or 50 hours. Use conventional oil for break in oil, no synthetic. WOT is OK for short bursts but not for extended periods. Otherwise than that drive as u normally would and enjoy.
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Incorrect.
 
You want a constant load on the motor. Avoid steady RPM's for extended times. Hook up to a fairly light trailer and hit some hills. Keep the boost and egts up.
 
I just broke in my fresh 6.4 build...after cam break-in, on a loaded dyno for 8-WOT runs for 90-sec each. Got it nice and hot...let it cool, wash rinse, repeat. After an additional 1,000miles, zero blowby.

That was under the direction, and observation of a Cummins certified mechanic.
 
If it is washing the oil off the walls, it wouls seal it quicker.

But. I have always loaded a fresh engine and worked it to seal it.
Clean up the smoke though! It does you no good and most likely it runs slower with smoke.
 
DirtyMaxx03 said:
You want a constant load on the motor. Avoid steady RPM's for extended times. Hook up to a fairly light trailer and hit some hills. Keep the boost and egts up.
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I agree with the above.

My practice has always been:
- After initial start, drive the vehicle. I always start in 1st gear, go from idle to 2500 - 3000 rpm at a medium rate (not slow, not fast), put the trans into 2nd, let the rpm fall down to around 1000 and then go back to 2500 to 3000 at a medium rate. Repeat this for all gears on a flat road.
- Let cool down to ambient.
- Go for a drive going up grades, this time time pushing the motor. Be hard on it, but not abusive. Do this for about an hour or so.
- Let cool down to ambient.
- Find yourself a trailer. Above mentions a "light trailer". I always use a "medium trailer" --> 7k pounds. Go for a drive, not beating on the vehicle, but as a typical driver until the engine oil gets warm. Which is about 5 minutes after the t-stat starts to cycle. Go find some grades, and climb them pushing the motor. Get her hot and bothered. Do this for about 30 to 45 minutes.
- Let cool down to ambient.

You will know when the motor is initially broke in when your ECT and EGT's come to a typical value. During break in they will be high due to all of the friction.

IMHO, break-in is not completed and done. After the above is completed, drive the vehicle like you stole it, within reason. There is a difference between being hard and being abusive. Don't be abusive. You can back down how hard you are on the vehicle/ engine as the engine reaches final break in. You'll know when this is as the time to reach operating ECT will start to remain the same and performance once at operating temp will be the same from start-to-start.

Most importantly, the above is my opinion and what I have personally used to break in engines whether built by me or by Cummins.
 
Some of you guys make this a lot harder than it really is. Start the engine. Check for leaks. Do whatever cam break in your supposed to. Then either slap it down on the dyno and make full power runs for a few miles or hook to a heavy trailer and drive the balls off it. Don't idle it more than you have to. Keep it hot and run them hard to get everything to seat. Pretty basic


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97rada said:
Some of you guys make this a lot harder than it really is. Start the engine. Check for leaks. Do whatever cam break in your supposed to. Then either slap it down on the dyno and make full power runs for a few miles or hook to a heavy trailer and drive the balls off it. Don't idle it more than you have to. Keep it hot and run them hard to get everything to seat. Pretty basic


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Do this ^^ I tried the take it easy and I was losing a qt every 1000 miles. After 8k still plenty of blow by. So after that I did several WOT runs and no more blow by.

Do not do "the no coolant cam break-in", tried it and it did not seal my rings and ruined a water pump. There is a thread on it somewhere here.
 
Keep a close eye on coolant temps and check the coolant level after initial start up as well. These motors can trap a good air bubble and cause a bad problem.... no coolant flow.

note* I don't have a coolant system vacuum and i wish i did.


also dont forget your first oil change soon after a few hard runs or some say after 500 miles.... especially if using a zinc additive with a new cam.
 
Ok good to know im doing a coolant bypass also so hope that helps coolant flow a bit. I will have a billet 66 on the truck also so this should be fun
 
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