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Engine Break-In Guide: 10 Tips to Help Properly Break in Your Engine

 

Proper engine break-in procedure is critical.

The right steps during this procedure can save your engine, your bank account, and ultimately your sanity. With help from the engine experts at ATK High Performance Engines and Summit Racing, this post will provide you with invaluable tips to help protect your engine during the critical break-in period.

hpe-hp40c_mlStart with an Inspection

Before you start the engine, ensure that all accessories, such as the headers, alternator, and power steering pump, are tight and check for any water or oil leaks. Even if your engine came as a complete, turnkey assembly, it’s best to check all major components such as the distributor, spark plugs, ignition wires, carburetor. These items could have been damaged or disturbed during shipping.

Lubrication Considerations

When installing an oil filter, fill it about half way with oil, lube the rubber gasket the surrounds the filter with oil, and then tighten by hand. Consider using a premium brand oil and filter—a cheap filter will not be cheap if it costs you an engine. Use a 5w-30 or 10w-30 motor oil with an engine break-in additive (ZDDP or zinc camshaft additive), especially with flat tappet camshafts.

Prime the Pump

To avoid dry start-up, it is best to prime the oil system with an engine-priming tool or a pre-luber, even if the engine has already been dyno tested.

jgr-01806_mh_xlUse Conventional Wisdom

Even if you plan on running synthetic oil, you should break a new engine in with a conventional, mineral-type engine oil for the first 4,000-plus miles. If you fail to follow this procedure, the piston rings may never seat.

Change Oil Often

On freshly built engines, you’ll need to change your oil and filter much more frequently. After using a break-in oil, you should change your oil at 50 miles, 500 miles, and 1,500 miles. Again, at 4,000 miles or so, it’s fine to switch to a synthetic oil if you choose.

Timing is Everything

Set the ignition timing after starting the engine. The starting point for most carbureted engines is 34 degrees before top dead center with vacuum advance disconnected at 3,000 rpm. Some experimentation with timing is required for optimum results with locally available fuel, but it should be between 32-38 degrees BTDC.

Take Care of Your Flat Tappets

If your engine uses a hydraulic flat tappet camshaft, keep the engine between 2,000 and 2,500 rpm, with no-load on the engine for the first 30 minutes. This is critical to break in the camshaft, although roller cams really do not need to follow this step.

SNN-10331_xlKeep Your Cool

Most often, the cooling system on a fresh engine swap will have a lot of trapped air, which will lead to wild temperature gauge readings and possible water pump cavitation. To help alleviate trapped air in the cooling system, fill the cooling system with a 50/50 mix of quality coolant and water a few hours before you plan on starting the engine. Leave the radiator cap off during this time. This tends to help purge a fair amount of trapped air before you start the engine. You can also use a lever-vent type radiator cap on your radiator so you can manually purge trapped air while the engine is running. Your normal cap can then be re-installed after the engine cools off.

Vary the Load for Initial Break-In

For the first 200 miles, drive the vehicle with varying speeds and loads on the engine. Occasional full throttle runs from a rolling start (2,000 rpm or so) to 4,500 will help seat components such as piston rings, but the engine should be cooled after doing this. Also, it is wise to check rocker and valve clearance after 150-2oo miles to insure adjusters are tight and lash is proper. Re-check again at about 500 miles.

Break-In Plan

Although it isn’t necessary, ATK says the following procedure will help speed up the break-in process:

  • Make five or six medium-throttle accelerations to about 4,500 rpm before letting off in gear and coasting back down to 20 miles-per-hour.
  • Run a couple hard throttle accelerations up to about 5,000 rpm and once again coast back down to 20 miles-per-hour.
  • Let the engine cool, change the oil and filter, and check the coolant level.
  • Drive the next 500 miles normally, keeping the engine below 5,000 rpm and minimizing operation at idle.
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27 Comments

  1. These break-in procedures all seem very good, except #4, don’t use synthetic for break-in. Many modern cars use a synthetic factory fill. A machining technique called “plateau honing” pre-breaks-in the jagged peaks of the honing process, which is what happened during break-in in the old days. This caution would apply, however, if your machinist does not use this procedure., In this case, #4 would still apply.

    • Unless this blog has been edited since you commented, #4 specifically says *don’t* use synthetic until after 4K miles.

    • Brandon Hardesty says:

      Yeah you’re absolutely right synthetic oil won’t let motor break in

    • Sarina Hernandez says:

      yes i have a question, I have a 1972 Dodge dart and the engine has been rebuilt. My lifters and rods and rings were replaced when my head gaskets blew which was right before the engine was rebuilt. After it was completed my mechanic (who was my friends dad) drove it to me. Well let me put it in his words “it runs great drove it at 102 mph all the down the hill (which is about 27 -30 miles). After i got it back it went to shop to rebuld the radiator. which was leaking profusely to begin with. then picked it up few days later and put it back in. Went to get coolant 3gallons of 50-50. And when we started her up she was knocking bad. worse than what she sounded like before. So my boyfriend checked out oil and to our surprise it was a milkshake once again.So we changed oil thinking maybe someone put water in with it and we were wrong cause it turned back again to milkshake come to find out the headgaskets have been blown again, and to boot the radiator has a leak again too. What can i do? can u please tell me. Thanks Sarina

  2. Loris Williams…… the rude @##$#@$ who has never made a mistake

  3. Robert Thiel says:

    Good stuff, but if your a local Bracket racer, like myself, break in is, 30 to 45 minutes in the garage, running, couple of laps around the neighborhood, as long as no one calls the Police, 2 to 3 low RPM passes, on a Wednesday night test & tune, back home at the Garage check everything over change the oil and back to full throttle.

  4. I dont baby any of my builds…I tell people I do engines for, break it in the way you’re gonna drive it…never had a failure. If you do your build right, checking all bearing clearances and such, should never have a problem. I don’t change the oil at 50 miles, it’s a waste of oil. Better to pull the filter, cut off the case and inspect it…no metal, you’re good. Install new one, too off the oil, run it to 500 then change and inspect filter..

    • Improper break-ins can cause failure. If a new engine is ran for a long time at a constant RPM a ridge in the cylinder wall can develop. The rods stretch more at the top and compress more at the bottom with higher rpms so when the rings hit this ridge it anti-pretty. Usually, only happens if people go for a very long highway drive right after the rebuild and don’t vary the rpms like they are told to! This is why you want to take it to the redline while breaking it in here and there. It will ensure that the cylinder wall doesn’t wear unevenly.

      I usually try to drive at least the first 100 miles on new engine but it’s not always practical.

  5. Keep a fresh fire extinguisher close by..seen a lot of close calls with fuel leaks on new motors. Once saw a fuel leak drip onto a drop light and burn up a corvette because there was no extinguisher anywhere in the shop…

  6. yeah & dont buy a performer intake if you have a holley d/p in my case i had to buy a adapter plate to keep the fuel from boiling and vapor locking my engine back then the fuel was ok to run

  7. Pingback: Issue with engine using oil - Pontiac GTO Forum

  8. sheemaroy01 says:

    First of all, being bored at work does pay well if you have a Smartphone and you browse through blogs.Amazing information with facts thoughtfully incorporated within. Definitely going to come back for more! 🙂

  9. I have caprice 1994 v8 4.3l
    change pistem and complete valves accessory and timing chain , honing cylinder and start
    does the EMC need to be programmed ?
    the mechanic I doubt he did not know how to put hoses in its original place
    need picture show details of hoses connection
    my car now run but rough idling I replace new Control Idle Air Valve and new map sensor and
    new egr and new throttle sensor

  10. has anyone used the Amsoil Break in Oil ?

  11. I have different clearances for race and street engines. Street engines require a longer break in race engines fo right on the dyno.

  12. Zeppo Jaworski says:

    If you read this man’s column why would you vary from his advice. He is the professional and knows right from wrong. No major automotive company in the world would disagree with his formula for breaking in an engine. You don’t break them in like you plan on running them. I have broke in many hundreds of engines on an electric dyno as well as water brakes and a few went into major race cars and we never abused them on break in. We ran break in engines for 18 hours with intermittent oil changes. That is how it is done professionally.

  13. I have a freshly rebuilt 350 engine that shakes while in gear (automatic) trans. is this normal until break in or is there something wrong?

    • could be a slight timing problem or the tranny could be causing the shakes, try to determine if the shakes happen when its in neutral or only in gear.

    • First, check it is not engine timing/misfire/etc. Overly-retarded timing can cause a sloppy and unstable idle and generally poor performance.

      Secondly, check motor mounts. Sloppy mounts are often overlooked in a rebuild and can appear to be an engine problem.

      If the vibration is definitively related to RPM, it may be possible you lost a bolt on the torque converter/pressure plate, or that they have come loose, but this is a worst case scenario. Make sure no “accessories” are causing the problem, like the alternator/power steering pump, etc.

      For automatics in particular, make sure the governor is clean and moves freely (with many older GM trannies, you can easily get to the governor under a cap held down by a spring clip; only attempt this when the TX is cold…you don’t need to remove it, just fiddle with it and see that the parts still move fairly well), check fluid level/condition (bubbles are no good, try letting the car sit undisturbed for a few days if you can, and try again), and make sure all mounts are correct and undamaged. If vibration worsens under load like a “stall test”, you may have a tranny problem. If it worsens with engine speed, you may have a mechanical problem (such as losing a bolt off the flywheel/flex-plate. If it worsens with vehicle speed (and is not caused by anything else), you have a transmission/driveline problem.

      Always recheck later to make sure all fasteners are still tight, just as you would recheck your lugs after changing a tire. Proper and tight engine/transmission mating is absolutely essential, and in many cars they work as a singular supporting unit.

      Fluid level in an automatic is critical. Do not under or over fill. Keep in mind that level reading may have do be done under certain conditions to be accurate, such as engine running in park for 2 minutes and after 5 miles of driving, etc. Your transmission may vary.

      I know it’s a bump, but for anyone else who stumbled upon this article as I did, it may be helpful.

  14. Sounds rational

  15. Sounds more like the torque converter may not be balanced correctly. some have weights welded to them for “externally” balanced engines, while other have no weights and the engine is internally balanced. Wrong combination and it will shake a lot, and tear up transmission input bearings and seals, as well as crank rear main bearings and seals too. Verify what your build is supposed to have, and then check those part numbers.

  16. Kekeli Buckner says:

    Very enlightening. Thanks

  17. Great read, however I’m wondering whether there would be any changes to the advice given for a motorcycle engine?
    Thanks

  18. How about a boxer engin specifically corvair cast rings (deves) 2000 miles on 10w30 still uses 1 qt per 2 hrs drive no additives witch weirdly enough is was the exact same issue before rebuild. Sent camera down cylinders no scoring. What the heck? Also first time using deves 4 piece oil rings installed exactly as instructed all cylinders seem to be burning oil going by look of spark plugs don’t think too much of deves 4 piece. Do you think it’s too late to run break in oil? Or should I toss the deves.

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