How you break-in your newly built race engine can greatly affect its subsequent life and power output, as well as the amount of cash left in the bank account for racing. There are many facets to an optimal break-in. The first aspect we should appreciate is that no matter how well or accurately the engine and its components have been machined and assembled, the engine will never be broken-in as built.

I have seen a number of really good engines that have had the edge taken off their potential power because the necessity for an adequately extensive break-in was not appreciated. I remember a dyno session with one well-known West Coast engine builder (and a good one at that) who announced that the engine would be broken-in by the time it had warmed up. Prior to firing the motor, I took the opportunity to use a borescope to look at the bores while the plugs were being gapped and installed. The block was machined at the same machine shop I used, and as expected, all the bores appeared to be in pristine condition.

After about a 10-minute warm-up at 2,500 rpm or so, this roller-cammed engine was declared ready to do some serious power pulls. Well, our engine builder friend had done several engines similar to this one, so ignition and fuel calibrations were close. The results of the first pull really impressed me. I had built a similar motor to the same basic rules the previous year, and this one topped mine by over 30 hp. After some calibration, that figure went to about 40 hp.

Obviously, this guy knew what combinations worked. Having announced we were all done and it was lunchtime, I took the opportunity to pull the plugs to see what the mixture spread looked like. I also looked at the bores while doing this, and they did not look good! There were fine scores in every cylinder and deeper scores in some. In less than an hour's running, this engine had completely bypassed the broken-in phase of its life and had gone straight to the wearing or worn-out phase. This meant its competitive life on the track would be shorter and less effective and a new high-dollar engine, or at least a rebuild, would be needed that much sooner. Had the need for a break-in been more clearly understood, this engine would have made more power and lasted longer.

The two prime factors we attend to during break-in are friction and ring/bore seal. Although important, components such as timing chains and bearings are very much secondary considerations. The whole purpose of paying extra attention to bores, pistons, and rings is to improve their combined ability to seal high-pressure gases above the piston crown with a minimum amount of frictional losses. The higher the intended engine rpm, the greater the horsepower loss is for a given frictional torque. Let's say we have a set of pistons and rings that are of a production style and have a combined 5 lb-ft more friction than a more race-orientated design. At 5,000 rpm, that extra friction will cost 4.7 hp, but the loss caused by that same 5 lb-ft of extra friction will be 8.1 hp at 8,500 rpm.

Like it or not, the last machining operation done on all the moving parts within your engine occurs after it is built. Those of you who have machining experience realize that machining a piece of steel can produce anything from an ugly finish to a smooth shine. It all depends on the tool shape, cutting speed, depth of cut, and the cutting fluid used. Using that analogy, what we are trying to achieve here is an assembled machining process (normally called break-in) that produces the smoothest surfaces within the engine. Since ring and bore friction typically accounts for half the friction within the engine, it makes sense to gear a break-in to more specifically address these surfaces.

Various phrases such as "the rings need to seat-in," or "the rings have not seated," are pretty common expressions, and I bring this up for one reason. In 44 years of building engines, I have not had one case in which the rings did not seat-in. The ring manufacturers I spoke with about this were very surprised, as rings not seating properly was one of the biggest break-in issues they had to face. At the end of each discussion, the conclusion was that I was one of those freaks of nature-a racer who actually read the instructions pertaining to bore finish and such for the rings in question. I am sure that using new rings on old glazed bores could be a problem, but I am also equally sure that the rings will seat-in just fine if everything is done right. The question is, what is right?

To get rings to seal and deliver low friction levels, the bores must be correctly honed with a finish to suit the ring material and subsequently cleaned. Even the more modern honing techniques and equipment can still leave a certain amount of honing stone debris in the finish. The first part of breaking in a bore is to see that it is absolutely spotlessly clean. I use a Scotchbrite pad intended for pot scouring and Gunk engine cleaner to both clean and prep the bore surfaces. When inspected under a microscope, even the best bore finish has jagged spikes of material that will tear into anything that rubs against it. When I clean the bore with an up and down action, the Scotchbrite pad lops off the peaks of these microscopic spikes. The amount of material removed with the Scotchbrite pad is a fraction of one ten-thousandth of an inch, so it's not really a measurable amount. The same treatment should also be applied to the ring faces.

So, how does this help the break-in procedure? After all, everything will smooth out as the engine runs. The key is the break-in procedure. When the newly machined parts rub over each other, there is microscopic welding and tearing. Each time a weld is torn, it creates another microscopic rough patch or surface wound that also needs to be broken in. In essence, the mating parts need to either very finely machine their mating counterpart or knock down the microscopic spikes to smooth the surface. If too much microwelding occurs too quickly, the surface finish is worn out rather than improved. We need to avoid too much speed and load to prevent excess microwelding and surface tearing. So far, the bore prep is off to a good start.

I use a lot of Total Seal rings, so when the Quickseat powder bore lube was introduced, I gave it a try. I used it on about a half-dozen engines, and it appeared to work just fine, but nonetheless I stopped using it. The very fine black composition of Quickseat not only stuck to bores like it is supposed to, but also my hands, cameras and white walls. This stuff is cheap. If you have any doubt about the rings in your engine seating in-use it.

Your carefully built engine is now ready for its first run. There are three places this can happen: in the car, on a break-in stand, or on the dyno. Running the engine in the car is the least costly option of the three, but going that route has only cost as an advantage. If the engine has even a minor problem, such as a leaky seal (hey, it happens), it has to come back out. It is really a great asset to break-in an engine prior to installing it either in the car or on the dyno, unless you happen to own your own dyno. Dyno time typically costs $80 to $100 per hour, and a proper break-in session with a post-break-in service can use two to three hours. After about your third engine, you will have paid for a professionally built engine break-in stand.

Regardless of where the engine is first fired, the perennial question is, should it be broken in on mineral or synthetic oils? Allowing that a successful break-in is an accumulation of build procedures as well as lubes and techniques applied during the break-in, I have found little difference between top-quality mineral or synthetic oils over the past 15 years. My policy has been to break-in for the first 20 minutes with a quality mineral oil, such as Castrol GTX. Its low cost figures into the equation pretty heavily considering it will only be used for 20 minutes before being dumped along with the filter.

I recommend using a quality oil filter because the amount of debris the engine creates in the first few minutes of running is at its highest. At this point, I cut open the filter and inspect what is inside. There will always be a certain amount of fine metallic particles, and these are hard to see. If you see particles that might have originated from bearing material, and they are not in the realm of fine particles, there is probably a problem with the bearings. If the engine is on a break-in stand, it does not take long to dump the oil and drop the pan to make a check on the bearings.

After 20 minutes on the first oil fill, the filter and oil are changed. Again, use a good mineral oil along with a quality filter for the second round of the break-in. This next fill should be run for about an hour to maybe an hour and a half with the engine progressively cycled to higher rpm. The engine should be up to about 75 percent of the rpm it will eventually reach. At this point, the sump should be refilled with the oil you intend to use during a race or dyno test. Make some provisional pulls once the engine is on the dyno. Work up to the redline to ascertain all is well, and then go for it.

Let's discuss in greater detail oils for break-in. EPA mandates placed on street usage oils have brought the removal of additives that are historically effective high-pressure lubes. This makes any off-the-shelf, street-type oil less effective as a break-in oil than it was just a year or so ago, which necessitates modifying this year's break-in procedure. As a matter of course, I always put Oil Extreme into the break-in oil. If you are not using a high-pressure additive, you might consider using a bona fide race oil as a break-in oil-especially if the motor is a flat-tappet cammed unit. Suppliers such as Redline, Joe Gibbs Racing, Royal Purple, and others have oils specifically blended for flat-tappet cams. The most critical time for a flat-tappet cam is the first 20 minutes. Such cams demand a lube with high pressure capability. If the springs have over 350 pounds of force over the nose, the cams need to be broken in with Comp Cams low-lift rockers and/or a softer break-in spring.

Cylinder Bore Specific Break-In LubesNow that we've handled the flat-tappet cam situation, it's time to consider the source of the engine's greatest frictional losses-the bores, rings, and pistons. A steady and lengthy break-in helps cut the final frictional level where the parts stabilize, and the same procedure also leads to the best cylinder seal. But there is something of a compromise going on here. We need a lube on the bores to cut friction and wear, but we do not need lots of oil in the upper cylinder or on the cylinder walls because the octane value of the fuel can be compromised and unwanted additional drag on the rings is produced. But the bores will experience more friction and wear without adequate lubrication, and we don't want that, either.

Here, it's worth taking a few pages out of Caterpillar's test portfolios. Quite a few years back, an experimental marine-sized diesel was giving the company severe problems with bore and ring wear. A rather unique and effective upper cylinder fuel additive was used, and the problem simply went away. I did some 250 hours of A-to-B tests on this additive about 15 years ago for an EPA report and found that in a worst-case scenario for the test engines concerned, ring and bore wear was axed by no less than 600 percent!

Here is how it apparently works. First, this additive (now commercially known as American Clean Energy Systems or ACES) must be mixed in very low concentrations with the fuel. When the combustion cycle takes place, the additive burns into a high-grade synthetic lube that coats the cylinder walls from the topside down with a lube layer just a few molecules thick. Remember, on the way down, the rings scrape much of the oil off the bores. The lube component is spread thinly on the bores with this additive, so on the way up, pistons and rings should not even touch the bores.

Over the years I have found this additive to be really effective at prolonging the life of rings and bores. Given a top-notch air filter, 2,000 racing miles result in near-zero wear on rings and bores. Last year, I tore down the engine from my GMC Sierra tow truck. The intent was to install a valvetrain and heads to complement the Magnusson supercharger that was to be subsequently installed. This engine had 106,000 hard miles on it (and I mean hard). I followed my own advice here, and as with all my other engines, the result was near-zero wear. This engine went back into the truck with the original factory rings and bearings!

T&L Engine Development
12303-A Renee Ford Rd.
NC  28163
Performance Racing Warehouse
Total Seal
BND Automotive (American Clean Energy Systems)
  • «
  • |
  • 1
  • |
  • 2
  • |
  • 3
  • |
  • View Full Article