by Joe Fournier
Here's what I do for break-in:
- 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.
- Drain oil while it's hot. Replace before starting again. If time allows, let engine cool and check valves.
- 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.
- 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.
- 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.
- 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.