Breaking In A New Or Rebuilt Engine Hard Or Not ?

[crazyoildude]

Being in the engine business i hear rebuilders talking some say break an engine in very gently others say push them hard What does everyone here believe?
After we rebuild them we run them for 15 minutes and then drive them for about a mile and tell the customer to drive it like you would any car.
I personally always believed in breaking a new engine in easily but most dont agree

 

[Shannow]

I believe in hard, but hard that's not 100% hard.

2,000-2500RPM no load for the cam, for 10-15 mins (and to check for leaks etc.

Hard acceleration (e.g. up hills), with high vacuum on over-run, so that any spots that get hot under4 pressure in the former, get cooled and lubricated on the latter.

I reckon that if you had access to a chassis dyno, you could combine the whole lot to a 20-30 minute complete break-in.

 

[Trav]

That sounds just about perfect!

 

[Eddie]

I believe in a medium break-in. First is to bring water & oil temp up by fairly easy driving for 20+ minutes or so. Then do several 5 seconds power pulls of up to ~3500 rpms while letting the engine run easy for several minutes between runs. Six or eight of these power runs will get the rings seated, which is the primary purpose. At this point you now need to burnish the sliding parts in the valve train and elsewhere and this is done by driving normally i.e. not babying or beating on it. I have used this method on lots of new engines and most were sold with well over 125,000 miles, running strong and without any measurable on-the- dipstick oil consumption. Ed

 

[widman]

If you think about what is happening in the break-in, you will never go the "hard" route. This is a period where the bearings are equalizing the surface, wearing in small areas that are not quite round to reduce turbulence and get good hydrodynamic lubrication. Running hard there will cause turbulence and cavitation.

It also works in the rings to the cylinders. Here is where you could take a little harder to push the rings out harder against the cylinders, but not too hard, as they are also taking out minute amounts of metal as they go.

First 50 miles or so I recommend gentle. Then change oil and drive moderately for next 600 to 1000. Occasionally pushing harder, always varying speed.

When it stops consuming oil (1500 to 5000 miles), it is broken in.

You will find this consistent (with the exception of the 50 mile change) with every new car manual printed (that I've seen). New cars are assembled under really strict cleanliness and torque, so there isn't as much of a need for that 1st change.

 

[The_Eric]

My thoughts

 

[BigCahuna]

I'll bet the conversation between you and your rebuilder would go something like this. After you inform your rebuilder that your motors not running right, they inspect it and ask if you followed their break-in procedure. You say no, I did what that motoman said, and broke it in hard like he said to. They would in turn say to you, then have HIM fix it then. I tend to follow what a company with thousands of motors under their belt,says to do then what some guy on the internet with a hundred or so motors under his belt has to say. What does he care if YOUR motor goes bad?.,,

 

[NHGUY]

Saw a brand new Camry with 20 day plates speeding down the highway passing everybody Friday going about 80 mph.I dont think that engine is destined for a long,trouble free life.

 

[pbm]

Eddie from Cape Coral seems to have the best plan, IMO....

 

[The_Eric]

This is why I almost never post in these types of threads. There is ALWAYS heavy opposition to this type mindset and an unwillingness to investigate.





Originally Posted By: BigCahuna
I'll bet the conversation between you and your rebuilder would go something like this. After you inform your rebuilder that your motors not running right, they inspect it and ask if you followed their break-in procedure. You say no, I did what that motoman said, and broke it in hard like he said to. They would in turn say to you, then have HIM fix it then. I tend to follow what a company with thousands of motors under their belt,says to do then what some guy on the internet with a hundred or so motors under his belt has to say. What does he care if YOUR motor goes bad?.,,



Not running right? Could you elaborate? Yes, of course telling them that I gave it a vigorous break in could end up with them not wanting to help. But it would be done arbitrarily - without any real investigation or fact finding.

Have you actually read the content of the articles?

While I don't have inside info on auto makers, I do have inside info on what John Deere does in their dyno test cells. Yes, it's a diesel, but the same principles apply... Guess what? they bring them to temp and flog them to WOT. This comes from a guy who worked the dyno cells at the Deere engine works plant in Waterloo Iowa.

Much of today's mind set is borrowed from yesterday's wisdom, when machining quality, techniques and materials wasn't as good as it is today. BUT, THINGS HAVE CHANGED, and still yesterday's mind set remains. What does it actually hurt? Nothing. BUT, the ring seal won't be optimal.

If an engine is going to have problems, it's going to have problems no matter how you break it in. There is no "wearing together of parts". If bearings are rubbing journals to the point of needing to be cautiously and gently operated, it's a bad thing. I've seen (personally) and read of countless other performance gas engines that are brought to temp on the dyno and flogged through various load cycles with no ill affect. I have even seen them torn back down after use in their end use vehicle and again, they were fine. In fact if you were to measure bearing clearances before putting a new engine into service and after 20k miles, you'd be hard pressed to find any difference. This, of course is ASSUMING accurate machine work and clean and correct assembly.

I have built numerous 2 cycle engines (yes, it's applicable - they still have pistons, rings and cylinder walls as well as a need for ring seal) and can attest to a vigorous break in vs. an easy one. The level of ring seal is quite evident. Both quantifiable (measured compression) and visually (blow by). Also, amazingly, the pistons didn't self destruct. If you like, I can provide pictures (my own) to illustrate the differences.

Bottom line... IF the machine work is accurate and the [engine] assembly is proper, then the engine will live a long life REGARDLESS of break in procedure. But a "hard" break in assures better ring seal than an "easy" break in.

 

[Jarlaxle]

When he built the engine, my uncle ran it half an hour at 2000-3500RPM to break in the cam. He then changed the oil, loaded a bunch of weight into the bed of his F250, and drove it about 200 miles through hilly terrain to load the engine.

It went over 150,000 miles, had <10% leakdown on all 8 cylinders, and ran perfectly right up to the moment the timing chain broke. (You will never convince me THAT was caused by the break-in method.)

 

[SteveSRT8]

Originally Posted By: The_Eric
BUT, the ring seal won't be optimal.

If an engine is going to have problems, it's going to have problems no matter how you break it in. There is no "wearing together of parts". If bearings are rubbing journals to the point of needing to be cautiously and gently operated, it's a bad thing. I've seen (personally) and read of countless other performance gas engines that are brought to temp on the dyno and flogged through various load cycles with no ill affect. I have even seen them torn back down after use in their end use vehicle and again, they were fine. In fact if you were to measure bearing clearances before putting a new engine into service and after 20k miles, you'd be hard pressed to find any difference. This, of course is ASSUMING accurate machine work and clean and correct assembly.
Bottom line... IF the machine work is accurate and the [engine] assembly is proper, then the engine will live a long life REGARDLESS of break in procedure. But a "hard" break in assures better ring seal than an "easy" break in.


Absolutely on the money. We have a machine shop in the family, and my 3rd generation expert engine builder BIL would strongly agree with this procedure. The bottom end is either right or not, you're not 'breaking in' anyting there, all you're doing is establishing the ring to cylinder wall seal. You gentle break in guys would flip if you could see a BRAND NEW 25k big block on the dyno running 10W oil at full power!

I own a known oil burner. Many think a large engine should use some oil, but mine does not use a drop, even on track days spent lapping Homestead at 150 mph!

Break it in hard. Just like Deere does, get everything up to temp and get on it. Use the higher gears for more load. The reward is a MUCH BETTER ring seal that will give you more power, less blow by, and lower oil consumption.

 

[cjcride]

Test drove a Honda Civic about 5 years ago. So new on the lot the salesman had to peel thin white "shrink wrap" off the leading edge of the hood etc.
Salesman harped on about the power and on the test drive he told me to Boot It [engine had been on for about 4 minutes] I refused and he insisted. Tried to tell him about the breakin period he didn't give a [censored], just thought my senses would shut off and I'd buy the car if we Booted It.

Didn't Boot it or Buy It. Drove nice though.

 

[demarpaint]

Originally Posted By: cjcride
Test drove a Honda Civic about 5 years ago. So new on the lot the salesman had to peel thin white "shrink wrap" off the leading edge of the hood etc.
Salesman harped on about the power and on the test drive he told me to Boot It [engine had been on for about 4 minutes] I refused and he insisted. Tried to tell him about the breakin period he didn't give a [censored], just thought my senses would shut off and I'd buy the car if we Booted It.

Didn't Boot it or Buy It. Drove nice though.


Trust me the lot boys booted it long before you were in it. Our guys did hole shots 2 seconds after starting them in 0° weather.

 

[mechtech2]

Originally Posted By: Shannow
I believe in hard, but hard that's not 100% hard.

2,000-2500RPM no load for the cam, for 10-15 mins (and to check for leaks etc.

Hard acceleration (e.g. up hills), with high vacuum on over-run, so that any spots that get hot under4 pressure in the former, get cooled and lubricated on the latter.

I reckon that if you had access to a chassis dyno, you could combine the whole lot to a 20-30 minute complete break-in.


This^^ is pretty good.

Most cylinder and ring pressure occurs in mid RPM, when torque is highest. Full throttle at mid RPM helps initially seat the rings. I'd avoid very high RPM for a while. It's gonna break in anyway.
Rebuilt engines are rarely as good as factory engines .-factories are great now.

 

[crazyoildude]

i own the shop

 

[crazyoildude]

most factories are great not all there are still failures

 

[Scott_Tucker]

I just bought a brand new Civic Si today and it will be broken in hard. Those who *really* know how an engine works know there is a scientific reason to do this.

 

[mechtech2]

Originally Posted By: Scott_Tucker
I just bought a brand new Civic Si today and it will be broken in hard. Those who *really* know how an engine works know there is a scientific reason to do this.


Oh, Puleeze!
Maybe you can sell your idea to the car Mfrs, who don't abide by this, nor do they recommend it for the new car purchasers.
Why? There is no need, just a bit slower break in.

 

[Scott_Tucker]

Actually there is no need to break in a new car anyway, they are already broken in from the factory. Modern engines have much tighter tolerances than they did back 20 years ago or when a machine shops rebuilds one today. There are basically 2 things that "break in". The piston rings and the bearings. Term "broken in hard" doesn't really tell you anything as it's not very specific. By "hard" I mean a specific procedure consisting of accelerating and decelerating the engine while holding it in a constant gear.

The procedure goes like this:

Holding the engine is a gear (like 3rd) drive gently up to 2000 rpm and then accelerate at about 2/3 to 3/4 throttle up to about 3/4 of redline. Then, completely remove your foot from the gas while holding it in gear so the engine is braking the vehicle. When you accelerate, gas pressure gets behind the piston rings and forces them outwards towards the cylinder walls. This knocks down any high spots on either the ring or cylinder and after break in the ring should be the same shape as the cylinder. When you decelerate, high vacuum in the cylinder draws oil up past the rings, cooling them and flushing any debris out.

The bearings have a property called conformability. If all the main bearings bores are not perfectly concentric, the soft babbit layer on the bearings is actually hydraulically deformed until they are concentric. Over a period of 500 miles or so the bearings work harden into their final state. This is why bearing start out looking a very dull gray but after they have been run in, they turn a shiny silver color. Now, here it is possible to hurt the bearings by over-heating them while they are work hardening. However, modern engines have such tight tolerance that this is usually not a concern. Not to mention today's material are significantly better than in the past. It is more important to have the rings broken in because otherwise the engine will be low on power and the engine might burn oil.

When I was tuning BMW's we would take a brand new car, put it on the Dyno and do many, many full throttle pulls. The engines that were broken in hard almost always produced more power due to a better ring seal.

That is my expert opinion. Other may disagree. Please feel free to explain why I am wrong. Debating is always good. The reader will take away from it what he feels is right.