When it's time to replace an engine's cylinder heads—whether you opt for new or remanufactured heads from the original equipment manufacturer or an aftermarket source—never assume the heads are ready to bolt on straight out of the box. In some cases, the heads may contain abrasive media (from reman heads being blasted during cleanup) or aluminum debris left over during machining of new or reman heads.
A Real-World Example
About a year ago, I ordered a pair of remanufactured heads (OE remanufactured purchased from a local dealership). The heads were loaded, including valves and springs. As each head was removed from the box and laid onto a clean workbench, I noticed quite a bit of aluminum particles that fell out of the ports, oil holes, and water jackets. Obviously, the heads weren't thoroughly washed and rinsed before assembly.
Unfortunately, I've seen this happen more than once—at my shop and at other shops. I've even experienced it with brand new OE and aftermarket heads.
Hidden Defects
Another issue involving new or reman heads involves potential leaks at valve seats, where the seats weren't machined correctly to allow perfect valve-to-seat mating. I've also come across a few heads where steel spring cups were missing, which would allow valve springs to dig into the parent aluminum. Granted, this isn't a common issue, but it happens.
Inspection Before Installation
The point is that you should never assume a fresh cylinder head can blindly be installed and placed into service. When you remove a head from its box, place it gently onto a clean work surface. Then pick the head up and see if there's any debris on the bench.
Even if it looks clean, run compressed air through the ports, fluid passages, and any threaded holes (open or blind). Also, run a vacuum test to check for valve leaks. If any leakage is detected, either return the head in exchange for another or take the head to a local trusted machine shop for valve and seat correction.
The Bottom Line
I'm not suggesting that all replacement heads have problems. In most cases, the heads will be fine. I'm simply stressing the need to inspect the heads before installation to catch any issues before placing the head into service. A contaminated head can easily cause severe internal engine damage, with the customer laying the blame with you.
Five minutes of inspection is far cheaper than a warranty claim and a damaged reputation.
