Engine Break-In Conflicting Advice

Earle

Earle

Senior Member
I just had work done on my engine (new insert rods, rings and cylinder honing). Refer to my earlier post about "rod bearing failure". This work, of course, calls for my having to go through a "break-in" period all over again. But I've heard, over the years, two very different philosophies about the break-in "technique".

One - My trusted engine restorer (who shall remain nameless so as not to bias your answers) - says to drive her gently, accelerate more slowly, NO LUGGING, stay under 40 MPH, change oil after the first 200 miles, etc. And do this for at least 500 miles. Violating these "easy break-in" precautions will result in poor ring seating and possibly scored cyl. walls. (35 MPH for 500 miles!...uugghhh... there goes my touring summer season...)

Some other "reputable sources" and "experienced A folks" (did I hear this in the Barn?!) say that the break-in period should be only about 100 miles during which you should drive it "hard", including up hills, high acceleration, etc. This causes the new rings to seat harder against the newly-honed cyl. walls and results in a faster, better seating and break-in.


My gut feeling and engineering intuition tells me #1 is the right answer!
Thoughts?

Earle
 
Earle said:
I just had work done on my engine (new insert rods, rings and cylinder honing). Refer to my earlier post about "rod bearing failure". This work, of course, calls for my having to go through a "break-in" period all over again. But I've heard, over the years, two very different philosophies about the break-in "technique".

One - My trusted engine restorer (who shall remain nameless so as not to bias your answers) - says to drive her gently, accelerate more slowly, NO LUGGING, stay under 40 MPH, change oil after the first 200 miles, etc. And do this for at least 500 miles. Violating these "easy break-in" precautions will result in poor ring seating and possibly scored cyl. walls. (35 MPH for 500 miles!...uugghhh... there goes my touring summer season...)

Some other "reputable sources" and "experienced A folks" (did I hear this in the Barn?!) say that the break-in period should be only about 100 miles during which you should drive it "hard", including up hills, high acceleration, etc. This causes the new rings to seat harder against the newly-honed cyl. walls and results in a faster, better seating and break-in.


My gut feeling and engineering intuition tells me #1 is the right answer!
Thoughts?

Earle
Click to expand...

I would follow the first advice.

If you were supposed to drive them hard during the breakin period, then there really is no breakin period.
 
You will get a ton of opinions on this question. I would go with what has worked for you in the past and heed the advise of someone you respect. Gar Williams
 
Earle. My engine builder really surprised me in 2006 had inserted engine done . as per him, button everything up , start car run it at 1/2 throttle about 1400 rpm for 10 hrs. next day tighten everything up and drive it the way i plan on. I asked him about slower speeds and he said drive it the way I plan on whatever speeds. He said it was now broke in during the 10 hr running. I did that and I run my car hard run about 1200 miles per month. speeds from 40 mph to 96 mph on road (only twice just to show someone it can do it) and also on dyno 65hp @ 2900 rpm THIS IS A 31 TUDOR
 
I see two issues, bearings and rings.

New insert bearings are already very flat surfaced and clearanced, unlike a tight babbitt job that is dependent on wear-off of much more metal without excessive frictional melting before a sufficiently large oil film surface area is established. People drive new cars out of the showroom and directly onto the interstate. :eek: With poured and bored babbitt that hasn't been finish honed or burnished you couldn't do that.

Rings are a different issue. Seating is dependent on grade of block iron, type of rings, and how the honing was done. Model A blocks are actually a bit softer gray iron than today's blocks, and will scuff easier from hard new rings still running on high spots. You didn't say if your pistons take stock rings, or use modern narrow rings like the pistons pictured in my avatar. Narrow rings seat faster, but require a somewhat different hone finish, generally a 'plateau' job. If your cyl's had a bore/ single step hone to finish size job and/or you have old style (1/8 wide) rings, go easy for several hundred. If you have modern rings on a two step job that leaves deep oil cross hatch scratches and fine finishes just the top edge off of them (forming a plateau between scratches), your rings will be broken in after the first 100 miles. A moly filled top ring is set in less than 50 miles.
 
Earle
You are going to get many opinions but in the end if you want any support for the work completed by your engine builder, you should follow his advice. I do not disagree with his suggestions and I think you should "trust your gut feeling".
I have rebuilt 36 engines in the past 30 months and I break-in most of them for 3-4 hours on an engine stand where I can monitor the temp, oil pressure, RPM, complete compression and vacuum testing and verify no rear main leakage.
My procedure is to start them and run at a high idle (1000 to 1400 RPM) for a few minutes while checking for oil pressure. Then I run them up to 1500 to 2000 rpm for about 15 minutes or until the coolant temp reaches 190 and then shut it down to let it cool. I re-torque the head while cool and start it up again. At this point of break-in, the engine may tend to overheat due the the rings seating. If the temp reaches 190, I shut it down again and let it cool a bit. Eventually, the engine will settle in and run below 180 and then I just let it run. I only have a gallon tank on the stand and the engine will typically run an hour on that amount. After 3 hours, I check cylinder compression and adjust the owners carburetor to provide proper idle. (Many times I have rebuilt their carb also.) I would take it easy on your new engine work. As a side note: I had an engine rebuilt many years ago by Ron Kelly, (RK Designs), Texas. He told me to take it easy when it was fresh, never to lug it (even after broken in) meaning always shift down on a hill and corners. He also told me if I threw the drivetrain into overdrive during the first 800 miles, the warranty on the engine was off. I had installed a Mitchell overdrive as part of the engine upgrade. 47,000 miles later...I've never had the engine out or the pan off. I follow his advice...never lug the engine. He explained that he felt excessive lugging would push the oil out of the rings...when I think about that statement...I have to agree.
Good luck with your engine!
Dave in MN
 
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Thank you, Gents, for all the good info. It seems that the most conservative and least damage-risk approach would be the "easy" technique. - Staying away from lugging (which I do anyway) and staying away from low/idle rpms to keep the splash action up. AND as Dave wisely pointed out, I ought to follow the instructions of the guy who did the work and who will be standing behind the warranty!

Here's where I feel kinda sorry for you shop owners and engine rebuilders out there - If a car is brought back for "problems" during these kinds of jobs, unless it's really blatantly abused, how can you ever know whether the owner really did follow your instructions perfectly or not? You guys are pretty vulnerable there, if only to maintain your reputation for service and keep up good customer relations! "The customer is always right!" (though we actually know otherwise at times...).

Earle
 
Earle,

Obviously you have to follow your engine builders instructions or he won't back up his work if you have a problem, HOWEVER.

I'm not one to keep my opinions to myself and I don't agree with either #1 or #2 option or some of the other posts on Ford Barn which contridicted each other.

I would call my method #1 1/2. On my 9351 mile trip last fall I started with a fresh engine newly borerd, new pistons, new babbit etc. I left at 5 AM wtih 4 miles on the engine, a full tank of ethenol gas and a crankcase full of Shell Rotella 15-40.

I drove conservativly but not slow. I went through the gears often, drove on freeways and exited every few miles againist compession to load the rings both directions. After a hundred miles or so, I used my overdrive and drove 50 to 55 mph.

By the time I got to Las Vegas I figured she was broken in and escalated the speed to 55-60 or even 65mph at times. Did I have problems? You bet I did. I had 7 flat tires caused by defective new tubes and I replaced a starter in Rapid City South Dakota.

Engine problems? None.

Would I recommend starting a long trip with only 4 miles on the engine? NO. It would be preferrable to put those 100 to 300 miles on around town with the same criteria, varying the speed and load. You want a lot of oil splashing around inside there.

Good Luck,

Richard
 
If you run it to fast (high rpms) during the breakin period you run a good chance of scoring the cylinder walls. And that would be aluminum from the pistons. The honed finish will help hold oil on the cylinder walls, but they are still a little rough and I believe this is what causes the scoring, if you run to fast. Yes, I scored mine.

So I'd follow his recommendations. May not take all 500 miles, but who knows.
 
On this subject, I just helped a friend replace a head gasket (it was silicone and blew between #2 and the center water hole). His engine had about 30 miles on it after a complete rebuild and I was amazed at the condition of the cylinder walls. It had new sleeves but they were not honed at all. Just straight fine lines going from top to bottom. I am asking, for him, just how will the rings seat? It has new pistons that rise about .125 over the top of the block and they are 80 over. Please comment.
 
When I rebuild a street engine for a customer, I BREAK IT IN.
Even if he does the R&R. I keep the distribtor cap till he is ready so there is no cheating and there never has been.
I have never had a comeback.
Over the years if you accumulate all the things that work and throw out all the things that don't work, you have a system that works every time.
 
Art Bjornestad said:
On this subject, I just helped a friend replace a head gasket (it was silicone and blew between #2 and the center water hole). His engine had about 30 miles on it after a complete rebuild and I was amazed at the condition of the cylinder walls. It had new sleeves but they were not honed at all. Just straight fine lines going from top to bottom. I am asking, for him, just how will the rings seat? It has new pistons that rise about .125 over the top of the block and they are 80 over. Please comment.
Click to expand...

On a new rebuilt engine with new sleeves, I would think you would have installed standard pistons instead of .080 over. Any reason for this?

I would also think the rebuilder should have made a nice crosshatch pattern for the rings.
 
Dave, in all those many engines you've rebuilt, what do you find is typical compression (with the Brumfield heads in particular) and difference between cylinders? And how do you see this change from initial check to post-break-in?
thanks!
Barry
 
Tom, The builder said he went 80 over for more power??? Would it be OK if the head comes off to score the cylinders with a tool that has a bunch of stones hanging off of wire bristles? I just can't figure out how these rings are ever going to seat.
 
Art Bjornestad said:
Tom, The builder said he went 80 over for more power??? Would it be OK if the head comes off to score the cylinders with a tool that has a bunch of stones hanging off of wire bristles? I just can't figure out how these rings are ever going to seat.
Click to expand...

A ball hone should work great. Of course the pistons need to be out and the cylinder wall washed down very well when done. Check the ring end gaps and the sides of the rings to make sure they aren't scuffed to the point where they may not properly seat again.
 
Art Bjornestad said:
On this subject, I just helped a friend replace a head gasket (it was silicone and blew between #2 and the center water hole). His engine had about 30 miles on it after a complete rebuild and I was amazed at the condition of the cylinder walls. It had new sleeves but they were not honed at all. Just straight fine lines going from top to bottom. I am asking, for him, just how will the rings seat? It has new pistons that rise about .125 over the top of the block and they are 80 over. Please comment.
Click to expand...


This is what the cylinders look like when the engine is broken in. If the cylinders were bored and sleeves installed there is no way it could have verticle lines and not be broken in. The boring would produce the lines around the cylinders then the hone would create the crosshatch. If the builder used a quality hone, the cylinders could be polished to almost a mirror finish before the pistons were installed. I would never hone a motor just because it looked like it needed a crosshatch. This is a perfect example of "if it ain't broke, don't fix it". Sounds like his engine is doing what it is supposed to.
 
Can anybody think of a situation where it wouldn’t be in an engine rebuilder’s best interest to specify an engine breakin procedure other than “be gentle”? (...at least until the warrantee period is over which is likely as long as they can see the licence plate of the car as it drives away:)). Isn't the key to find a balance between doing things that are good for seating the rings while not harming the babbit which is why lugging is such a no-no?. Probably the logical answer to this question is "all things in moderation"?

Excerpt from Ron Bishop, "Rebuilding the Ford Flathead," which has appeared in instalments in Skinned Knuckles

There's one thing certain about breaking in a rebuilt motor; if you ask a dozen different people what's the proper way to do it, you'll get a dozen different answers. Everyone seems to have a secret formula for breaking in a motor, and he's con­vinced that his is the only right way to do it. There seems to be one common element in all of them; everyone will agree that the most important factor in breaking in any engine is the seating of the pis­ton rings.

Getting a good sealing surface between the rings and the cylinder wall is what determines whether or not the engine will burn oil and also whether or not is will make horsepower. The best way to establish a good ring seal is by running the engine at varying rpm for the first few hundred miles. Be sure to spend some time in deceleration as well as acceleration during the break in. The ring seal is governed by the gas pressure exerted on the rings, and that pressure is determined by engine speed. Running at a constant speed will generate a balanced pressure and may lead to polishing of the cylinder walls. Therefore, continually varying the speed during break in is of importance. The accel­eration/deceleration cycle is necessary because this will load both sides of the rings against the walls.

As soon as the motor is started it should be set at high idle which will allow oil to circulate through the engine. Oil pressure is important, so keep an eye on the oil pressure gauge. Also keep a close watch on the engine temperature gauge to avoid any chance of overheating which could dis­tort the internal components at this critical time in the engine's new life. After the engine has reached operating temperature and runs for 20 or 30 min­utes, recheck the ignition timing and adjust the carburetor for correct idle speed. Shut off the engine and retorque the head and manifold bolts. Check oil and coolant levels.

Don't take any long trips and don't run the engine at extreme rpm. After the first couple of hundred miles, change the oil and oil filter. It's also a good idea to spend some time checking the engine compartment for loose belts, hoses, elec­trical connections, and so on. Once the 200 mile mark is reached, you may go ahead and run the engine the way you plan to drive it. If it's not broke in by the time you reach the 500 mile mark, it probably never will be.
 
A lot of people do not understand that a properly honed cylinder bore with cross hatch marks is actually smoother than just a straight bored cylinder that has not been honed.
Rings will not seat properly on a glazed cylinder either.
Take a penny and drag the edge of it up a straight bored cylinder, then with another edge drag it up the properly honed cylinder. Much better surface for ring sealing.
While you are running this test, try the same proceedure on a glazed cylinder.
 
OK, Gents, Two posters have now mentioned it and I have to try to get some clarification - or maybe offer some clarification? : I'm paraphrasing here, but the statements were like this: "During break-in, be sure to spend some run time decelerating and coasting against compression. This will reverse the pressure on the rings and load both sides of them to help them seat better."

If the posters are implying that deceleration and coasting against compression causes the gas pressure on the rings to switch from coming from the top down to coming from the bottom (crank case) up, I beg to differ.

The pressure on the rings is ALWAYS in one direction - from the top down, even when "coasting against compression." There is no way, especially in a vented crank case, to develope and maintain gas pressure from the bottom up against the underside of the rings to "reverse pressure" on them. The only thing you're doing by letting off the gas and coasting against compression is depriving the combustion chambers from a supply of gas to ignite. This causes the pistons to move upward on the compression stroke only against non-combustable "air" resulting in no "power stroke". This air compression effect is what you feel as a "drag" or resistance in the engine that slows the car down (like a "Jake Brake" on eighteen-wheelers?). Maybe it's this lack of ignition and the resultant lower pressure on the rings that the posters are referring to as varying or "reversing" pressure to help them seat. But the term "reversing the pressure" on the rings is misleading. It is not literally reversing.

Steer me right if I'm off track! - but I don't think I am!

The nature of the gas pressure on the rings in one thing. But I am still trying to reason out in my mind why constantly varying the force with which the rings press agianst the cylinder walls (accelerating then coasting, etc.) will result in a better break-in than loads that are more "constant" (long trips at one steady speed, etc.).

Earle
 
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