Secrets on How to Break an Engine In for MORE HORSES

Here is what we have always done on race engines.

On roller cam engines we.......
Fire the engine and run it at roughly 2000 rpm for three to five minutes. This allows for oil and coolant circulation, checking oil pressure, verifying/setting initial timing. Once the engine is up to around 180 degrees and everything looks good we shut it down. Change the oil and filter. We use standard Valvoline 10w30 oil in the initial firing and the following runs. We cut open the oil filter to double check for metal. Load the car up and head to the track. We make four to six hard runs on the car to seat the rings. Typically, we see the mph numbers come up as the rings seat. It never takes over six runs to get them set. Change the oil (Royal Purple regular 10w30) and filter (Motorcraft FL series). Check the valve lash and go have fun.

Flat tappet cams require.......
Fire the engine and immediately bring the rpm's to 2500. Keep a very close eye on coolant temperature. Run the engine for 15-20 minutes to break in the camshaft and lifters. Vary the engine rpm by 300-500 rpm every five minutes. Our ranges are from 2500-3500 so the oil splash is directed to different areas of the cam/lifters. We also try to keep the engine below 210 degrees during this process. (One key thing here is to use a lighter valve spring if the spring pressures are up there a bit. Keeps from flattening a lobe.) Once the cam break-in period is done, change the oil and filter (again....Valvoline 10w30) and check the valve lash. Go to the race track and make five to six hard runs on the car. Once you see the mph numbers settle you can change the oil to synthetic (again...RP 10w30) and go play.

Street engines get the same treatment. If you can't go to the track then find a 30-50 mile trip you can take. After the cam break in go hit the road. Vary your mph from 55-70 mph if possible. Do this for 30-50 miles and find a place to get a Coke. Let the car sit for about 20 minutes then come on back. After you return you can change the oil/filter to whatever oil you want to use and you are good to go.

Well.....
1) No, they are not. The term "race engines" has far reaching coverage. This could mean bracket race engines, high rpm small blocks, monster big blocks, blowers or turbos or nitrous, etc. Just for example sake, Dad's 512" big block has gone four seasons with nothing other than a valvespring change at mid-season (around 75 runs), plugs and oil/filter. Still leaks less than 6% in all eight holes.

Most of my modular engines were built as race-only engines but found their way onto the streets.

2) Roller rockers maybe. Roller cam bearings are not nearly as popular as you think.

3) Loose engines come apart quickly. Ours are built to very close tolerances. Just because you are running the piss out of an engine does not mean you set it up with loose clearances. Daily driver or race engines....you can't set rings "loose" either. It'll never seal.

 

Sounds like a reasonable approach to race engines.
Especially the part about flat tappet cams.
Your take on street engines is more or less what I was getting at too, varying things alot.

Concerning "loose rings", I was refering to low tension rings that are often used in racing.

 

Things to consider during "break-in"

The max height the compression ring sees in the cylinder is directly proportional to the RPM the enigne sees. Higher RPM stretches the rod more pushing the comp ring up. If the engine does not see this max RPM during your break-in procedure the first time it will see it is when you hammer the engine. This means you will have a transition area in your cylinder that the compression ring will travel over. Most of the time, not a super big deal, but it can be avoided by maxing sure your engine sees max RPM in the first tank of gas. Granny driven cars will develop a carbon deposit ring or ridge at the top of the hole. The first time junior gets in and romps on it he crams the comp ring into that carbon ridge and damages it.

Secondly, nothing "wears in" on the engine during break in. If something is wearing, then there is nothing to stop it from wearing. What does happen is microscopic deformation of the metal. Any high spots will be flattened out and fill in the low spots. All at the microscopic level.

The myth that race engines are put together "loose" comes from the use of forged pistons that have a high rate of thermal expansion compared to cast or hyper pistons or reinforced forged pistons. An engine with forged pistons will generally have a larger piston to wall clearance than a street engine when COLD, and have the same piston to wall clearance as a street engine when HOT. All bearing clearances are the same. This is because you are shooting for an oil film thickness. Race engines are put together with more attention to this clearance and are generally much closer bearing to bearing tolerance wise than a street engine that is put together with whatever comes out of the box. Same thing for ring gaps, deck clearance etc.

Not all race engines will run low tension rings, and very rarely is it ever the compression ring. If you want your bracket engine to hold together for a long time, then standard tension oil rings are what you want.

If you are running a stock class, and are trying to squeeze max HP per CI out of your engine, then you run a very low tension oil ring pack and burn lots and lots of oil compared to the bracket or street engine. Low tension compression rings will only result in more blow-by and power loss. Not worth the couple extra ponies you get from lower tension. 25 in-lbs of resistance in the short block is what we shoot for as far as ring drag goes. The higher RPM you run, the more important this number is as power loss will increase with speed.

 

The thing that no one here is discussing is the fact that the breakin procedure will be slightly different depending on what type of parts are in the engine. The item that most affects breakin time/method is the type of piston rings used. Chrome-faced rings take forever and a day to fully seat, but when they do they are not affected by dirty cylinders and dirty oil. They were often used in tractors and off-road vehicles. Cast iron rings often require several hundred miles to seat, are inexpensive (that's why most OEMs used them for about 70 years), and hold up for 100,000+ miles. The longer runin time required to seat these types of rings are what lead to the use of non-detergent oil for breakin, it was felt that keeping the cylinder walls "rough" helped to seat the harder cast iron and chrome-faced rings. The idea of frequently varying rpm during breaking, rev up to 4000 or so rpm then let off the throttle, is to alternately flood and then starve the rings/cylinder walls with oil to help seat the harder rings. Nowadays, moly-faced top rings are popular with a cast iron second ring. The moly-faced ring seats almost as soon as the engine starts, the cast iron second takes a little longer, but combustion is basically being sealed by the top ring. Engines with moly-faced rings are good to go a lot sooner than than those that use the harder rings. OEMS like 'em 'cause the quick sealing makes for better emmisions and fuel economy numbers.

 

Of course it is wearing in. At the microscopic level maybe, but it is wearing in and that is the bottom line. No one ever said it was wearing out.

No myth.
Yes close attention is paid on clearance. Blueprinting is the process.
However, race engines are generally set up with more clearance than stock specs. There have even been many threads here on the subject. Probably in the Drag forum, don't recall.

 

breakin

I worked as a tech. As did my uncle for 45 years at a Ford dealership, who did it the same way. And if you think they take it easy on that vehicle from the factory to the parking lot to the train to the truck, you'r ein for a big surprise. The drivers get paid for how many cars they move. They don't even let them warm up. Just start them and then race each other to the parking spots. I've watched for years new cars and trucks offloaded at Seattle and Tacoma ship docks and then loaded on trains and believe me your drive train is hammered pretty good by the time you even see it.
Bottom line IMO is drive it. By the time the cam is broke in, leaks are fixed, warmed up, and timing setup, if it was going to happen, it would have by now.
The problem with dealerships isn't hammering someone's car it the charging of parts not replaced, charging for work not done and ripoffs in the sales dept.

 

forgot

And as for dealerships, it's stealing from the coin box and other things left in the car and video taping how stupid you are in someone's car as those 2 fools did a few years ago.

 

Dont know if it applies to car engines or not but every new snowmobile i had that the engine overheated (from idling too long) always seemed to run better.