The right time to reject a wrong part is before it is fitted. Once the engine is open, the cost is labour and downtime, not the price of the part.
At the bench
- Match the invoice part number to the stamp on the part
- Check the box says OEM or names the aftermarket brand you ordered
- Look for shipping damage on castings, threads, and connector pins
- Compare gaskets to the old set, port by port
- Keep seals in the bag until the housing is clean and ready
If the number does not match, stop and ask. Supersessions are normal. A supplier should be able to explain the new number against your serial. Silence is not an explanation.