Engine Break-in

by Joe Fournier


Here's what I do for break-in:

  1. Immediately upon starting, run engine up to 2000 rpm for 20 minutes. Watch oil pressure and temp gauges. You're letting parts machine themselves to each other for preliminary fit.

  2. Drain oil while it's hot. Replace before starting again. If time allows, let engine cool and check valves.

  3. Inspect drained oil for metal particles. React accordingly; check for magnetic properties to distinguish aluminum and brass from iron. Aluminum = bearings...some wear is expected, but no chunks. Brass = timing gear or valve guides. Shouldn't find much of this, if any. Iron/steel = crank, cam, rings, cylinders...definitely no chunks, but I'd expect *some* of this in breakin oil.

  4. Run engine for 5-10 miles doing the drive up to 55; then wind (down-shift) down to 20 mph...at least 5 times...as many as 10. You're letting parts further machine themselves to each other with the emphasis being on the cylinders, which must machine themselves under load because their position/geometry is slightly different at different RPMs...thus, the variance in RPMs and the downshifting. I don't fully understand this, but Bob Hoover instructed me to do this and I do it religiously. I consider this as important if not more important that the 20 minute breakin.

  5. Let sit over night. Check valves.

    I record all valve settings (per valve) and maintain that information for the first 300 miles. I check and adjust valves at the following times:

    after 20 minute break-in
    after 5-10 mile break-in
    at 25 miles
    at 50 miles
    at 150 miles
    at 300 miles

    If I notice trends, I check more often. Since work is about 25 miles round trip, I usually get pretty close on these.

  6. At 300 miles, pull the engine and retorque the heads. This is a step many people skip, but I'm not inclined to. It will tell you a lot about how your engine is running and is neccessary to assure engine longevity and reliability. It gives you a chance to tighten up tinware and do those things that you meant to do but were in too much of a hurry to do the first time around.


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