The lubricity (slickness) of synthetic oil is too great to allow the friction necessary for the rings to seat (conform to) the cylinder walls. The cross hatch of the cylinder walls act like a cylindrical hone for the rings. However, if the cylinder walls are too slick and the synthetic oil continues to provide a good friction barrier, this honing/seating effect won't take place.

The good news is that individually built performance engines (and production engines produced in today's CNC controlled environments) are built so close to the nominal (ideal) design tolerances for clearances, roundness, etc. that a traditional break-in protocol does not really need to be followed (even though manufacturers recommend it).

Steve

 

Lubrication is VERY important to the break in period. You dont want her moaning and making noises that are unacceptable during this time.

 

Aint that the truth

 

Dino oils are more than adequate lubrication for the break-in period, synthetics advantage is in that they last longer and that they provide greater start-up protection. For the first one, you are changing the oil after 500 miles or somewhere thereabouts, for the second you are priming the oil system on your engine with a special priming tool, so both of the advantages of synthetic are negated and you are left with just the disadvantage, cost. If you're the kind of guy who MUST HAVE synthetic for everything including the break in period. Go with a synthetic blend, its a little easier on the wallet and will provide you with startup protection just like a full synthetic.

 

I find out a good answer someone needs to do a leak-down test on a freshly built motor before start up. Break the motor in and do leak-down test at various points (ie. 20, 50, 100, 500, 1000 miles etc.) and see when the rings actually get fully seated (or at least 80-90%). That might help us with this subject.

 

Subscribing, and I mean checking every hour.

I'm having a motor built and it will be dyno-tuned and then driven 400 miles home.....advice? At best I plan to stop after every 100 miles or so and take a long time eating, or shop to let the engine cool and then continue on. Good idea? Bad idea?

 

If you are having it dyno tuned right away, everything should be seated before you start your ride home. I don't think the heat cycling will matter at that point.

 

Yeah, I am going to have to go ahead and disagree with you here. Synthetics will work just fine to break an engine in...they are no slicker than dino oils. But if you follow most break-in procedures it turns out to be much more costly with Synthetic than dino.

Now for break-in procedure. I don't have my own company or build motors for big time racing names but I do build my own motors and break them in myself and have done this since my first flat 4 VW motor. The mototune way is very close to what I do/have done for years. First I run the motor up to full temp (2k rpm for flat tappet and 1k for roller) while checking for leaks and funny noises. If everything checks good I let the motor cool to at least the low 100's. Then I fire it up again and run it up to temperature...after that I hammer the **** out of it for 20 miles. Change the oil and filter. Hammer the **** out of it for another 100 miles. Change the oil and filter and enjoy. If you don't have full cylinder pressure after the first 15-20 minutes of run time you won't ever have it. Remember, pressure and heat seat your rings not 5000 miles of driving like a *****. Tony Schumacher does not run his motor around at under 2500 rpms for several hundred miles and neither should you.

BPD

 

This will need to be done, with the least amount of variables possible. all test will need to be done with the motor cold since the first test will be cold before the motor is ever fired. Also this is going to cause the readings to already be off due to the fact you will always get a better seal when the motor is hot. Another thing is the amount of oil in the cyl to help it seal will be hard to make sure it is the same every time.

 

Good point...It would be hard to keep it consistant and get the data that we are looking for.

 

Not exactly the same..but both Continental and Lycoming both have very similair and very specific break in procudures for new engines. The basics of the procedure is to start it...check all parameters and for leaks. Then run it up to a percentage of rpm (like 50% of max rpm) for 10 minutes then take it up to 80% or max rpm and let it sit for 30 minutes. At that point the engine is ready to fly.

Of course these engines have props attached and will have a load, but the gist is that babying them for long periods is not part of the procedure. And premature engine failure on an airplane is not an option.

The reason i posted that for comparison is because this is the only technical data from a reliable competent source that I have ever been able to look up for engine break in procedures..

Take it for what its worth.

 

makes sence.

 

Are those standard piston combustion engines? If so, it follows the break in hard theory. The prop keeps the engine loaded up at any given rpm.

 

When it comes to an LS1 I agree.

If breaking in an LS1 on synthetic oil was a problem, then you'd see plenty of issues with C5s, since the factory fill was M1 5W30.

As a matter of fact, synthetic 5W30 has been the factory fill in the Corvette issued LT1s going back to 1992.

 

That is what i will be doing with my engine

I will pre-heat the oil to 70°C and water 70°C on inital startup,rotate the enegine by hand to get oil in the pump,start it and keep it constant at 2000rpm+ for lubrication of the rockers and lobes of the cam for the first 5min

Idle and check everything,go for a Nice easy drive,no high rpms around the block a couple of times

Change Oil and Filter and do a leak down test and note the numbers,Drive 500miles with steadily increasing the rpm and breaking down with the engine

Change oil and filter and do a leak down test and compare the numbers,keep doing this untill the leak down test in constant

 

Break-in procedures are guided by a myriad of entirely different requirements. A flat tappet cammed motor needs a specific break-in for the cam. A new car needs a break-in for the trans and rear gears. Both of these are entirely different than what the rings need for optimal break-in. If you are putting a roller cammed motor in a car that already has the rest of the drivetrain broken in, run it like you stole it as soon and as hard as possible for proper motor break-in.

 

Noob here.

I feel compelled to chime in. I'm a gunmaker and machinist. Worked in aerospace for a number of years making little wigits.

I also used to be shop maggot for a very talented, pain in the ***, engine builder who set the Comp E world on fire back in the early 90's.

Richard Conley.

Lets examine a cylinder bore from a machinists stand point.

Modern bore finishes are obtained using silicon carbide stones. The most popular being from the Sunnen Corporation.

Silicon Carbide stones cut the iron bore liners cleaner. They leave less of a "burr" down at the microscopic level.

These little burrs used to wear on a ring surface something fierce. The lapping action of the bore scuffing into the ring is what used to require a long break in period.

In the 70's and 80's chrome became a material used on rings. Not done much (if at all) anymore. What is chrome? It's nickel and chromium. Two very tough, hard materials.
Suffice to say it takes a great deal of break in for this ring material. The advantage?

Once broken in, it has a high thermal resistance. Chrome puts up with heat. It's why the military requires it inside machine gun barrels and for MIL spec M-16's and M-4's.

Moly rings. Moly is great stuff. Tolerates heat, it's thermally conductive so it transfers the heat to the ring core material (iron) and it's porus so it holds oil to further reduce frictional drag.

Top rings are generally barrel shaped. Why is that? Pistons move up and down right?
It's unrealistic to assume that the ring is going to stay perfectly perpendicular to the bore axis. They deflect like a spring. Cylinder pressure pushes down, pistons moving down cause them to deflect in the opposite direction. They move back and forth constantly over the course of a cycle.

So why the barrel shape? Put a ball on a table. it is always tangent to the table surface right? A barrel shaped ring surface does the same thing on the bore. A flat ring would only have optimum surface contact when the piston was motionless at TDC and BDC. (and when the engine wasn't running)

How does this come into play? With silicon carbide honing stones followed by flex hone dingle ball hones, the surface prep of the bore is as good as it's going to get short of coating/plating with titanium aluminum nitride, PCBN, TIALN, TIACLN, yada yada.

these coatings are not new, they've been used in CNC machine tool production for years.

I think breaking in a cylinder bore/ring set up is nothing more than clinging to old school practices that just won't go away.

As for bearings.

Plain bearing systems rely on hydraulic pressure to operate right? Oil is squished in between the crank and the main. The crank and the rod. The cam and the cam bearing.

If the engine is made right it shouldn't ever really touch should it? Realizing this is not a perfect world, we know it does from time to time.

Is breaking in the engine helping to avoid this at all?

I have to wonder.

Don't claim to be a know it all, I'm sure I probably sound like it. Just trying to be helpful.


Best of luck.

NC

 

NC,
That's a thoughtful, well worded post that adds to the discussion. This is the kind of thing that this forum was really designed to do.

Thanks for your input.

Steve

 

nice explanation NC, well put

 

My break-in procedure: Drive it like you stole it. (aka Ride it hard, put away wet or drive like there is no tomorrow, etc. etc.) Then change the oil after a short time. Repeat. Simple.