Model: WP7 / WP8
Part Number: 1004744376
Brands: Weichai Power
Engine Model: WP7, WP7H, WP8, WP8H
Engine Type: Diesel
Scope of application: medium and heavy trucks, buses, construction machinery, generator sets
Rings seal combustion gas, conduct heat from the piston into the liner and scrape oil back to the sump. On the Weichai WP7 and WP8, set 1004744376 provides two compression rings and one oil control ring per piston, sized to the groove geometry of these engines.
Worn rings do not stop an engine; they make it tired. Oil consumption rises, crankcase pressure builds and performance fades as gas escapes past the piston. Owners often blame the turbo first, which is why a compression test and a blow-by check come before any part is ordered.
The set fits WP7, WP7H, WP8 and WP8H engines in trucks, buses, loaders and generator sets. Confirm the piston part number and whether the engine is standard or oversize. Mixing sets between variants is a common cause of oil consumption after a rebuild.
The top ring is barrel faced and chrome plated for the highest temperature and pressure. The second ring is taper faced to scrape oil and support gas sealing. The oil ring uses two chrome rails with an expander spring sized for the correct radial tension.
A tight gap breaks the ring when it heats, and an oversized gap allows blow-by that no tuning can remove.
If the bore has a ridge at the top of ring travel, replace the liner instead of fitting new rings into a worn bore.
New rings cannot fix a worn piston. Measure groove width with the old ring and a feeler gauge; an opened groove lets the ring flutter, which breaks it and damages the land. Carbon packed in the groove corner also prevents seating, so clean properly rather than scraping the surface.
Check the crown for cracks around the bowl and the skirt for scuffing. A piston that has been hot may look acceptable but has lost hardness and will fail again soon.
New rings need cylinder pressure to seat. Gentle running glazes the bore and leaves rings skating on a polished surface. After assembly, warm the engine and apply moderate load in cycles, varying speed. Change oil and filter after the first hours to remove metal produced while rings and bores mate.
Match the piston part number, bore size and engine rating. Standard and oversize sets look similar and cannot be interchanged. For a rebuild, order rings with liners and pistons as a matched set, which removes clearance uncertainty.
Oil that passes the rings burns in the cylinder and raises particulate emissions. In markets with emission testing this becomes compliance, not just maintenance. A failing oil ring often shows as a slight haze under load rather than visible smoke, so oil consumption records are the better early indicator.
Clean air and correct oil keep rings alive. Replace the air filter at interval, keep intake hoses sealed, use the specified oil grade and change it at the severe-duty interval. Fix overheating promptly, because heat softens ring tension.
Ring gaps must be measured in the liner the ring will actually run in, with the ring pushed square to a depth near the bottom of ring travel. Measuring in a different bore, or with the ring tilted, gives a reading that is wrong by enough to cause a failure. Use a feeler gauge set and record every gap for reference.
If a gap needs adjustment, file the ends square and deburr them before refitting. Never grind a ring by hand against a bench grinder, because the ends will not be parallel and the gap will open unevenly as the ring heats.
One set covers one piston: two compression rings and one oil ring.
Only if the bore is within specification and shows a proper cross hatch.
Only if the measured gap requires adjustment.
Glazed bores, wrong gaps or rings fitted upside down.
Browse the Weichai piston and components category, and pair the rings with the WP7 and WP8 piston 610800030035 or the WP7 and WP8 cylinder liner 610800010503.
Weichai WP7 Piston Ring (1004744376). These rings are the interface between piston and bore. Their radial tension and face profile decide whether the engine burns oil or blows it out of the breather.
Confirm the ring set matches the piston groove width and the rating. Rings are specified per engine rating, not by bore diameter alone.
Numbers beginning 1004 are numeric-series numbers used on later WP7 and WP8 production, where mounting detail changed without a change of nominal type. On this engine, confirm the WP7 application against the engine plate before ordering.
Measure end gaps in the bore the ring will actually run in, with the ring squared by the piston crown. Measuring at the top of the bore or in a different liner gives a false reading.
Ordering note. Lead time depends on whether the item is in stock or has to be produced; the position is confirmed before the order is accepted rather than after payment.
Related reading: Piston Ring Selection: Gap, Tension and Bore Condition
| We Are 30 Years Diesel Engine Parts Supplier | |
| Brand | EPID |
| Warranty | 12 Months |
| Condition | 100%New |
| More Models | Weichai: WP7, WP7H, WP8, WP8H, and other Weichai series. |
| Shipping | By sea / air / express (DHL, FEDEX, TNT, UPS, EMS) |
| Packing | Standard exporting packing or as required |
| Payment Term | L/C, T/T, Western Union, Trade Assurance |
| Delivery Time | 3-7 days (depend on order) |
| Selling Point | 1. On-time Delivery 2. Genuine Quality Assurance 3. Professional Supplier |
The top ring is barrel faced and chrome plated for the highest temperature and pressure. The second ring is taper faced to scrape oil and support gas sealing. The oil ring uses two chrome rails with an expander spring sized for the correct radial tension.
A tight gap breaks the ring when it heats, and an oversized gap allows blow-by that no tuning can remove.
If the bore has a ridge at the top of ring travel, replace the liner instead of fitting new rings into a worn bore.
New rings cannot fix a worn piston. Measure groove width with the old ring and a feeler gauge; an opened groove lets the ring flutter, which breaks it and damages the land. Carbon packed in the groove corner also prevents seating, so clean properly rather than scraping the surface.
Check the crown for cracks around the bowl and the skirt for scuffing. A piston that has been hot may look acceptable but has lost hardness and will fail again soon.
New rings need cylinder pressure to seat. Gentle running glazes the bore and leaves rings skating on a polished surface. After assembly, warm the engine and apply moderate load in cycles, varying speed. Change oil and filter after the first hours to remove metal produced while rings and bores mate.
Match the piston part number, bore size and engine rating. Standard and oversize sets look similar and cannot be interchanged. For a rebuild, order rings with liners and pistons as a matched set, which removes clearance uncertainty.
Oil that passes the rings burns in the cylinder and raises particulate emissions. In markets with emission testing this becomes compliance, not just maintenance. A failing oil ring often shows as a slight haze under load rather than visible smoke, so oil consumption records are the better early indicator.
Clean air and correct oil keep rings alive. Replace the air filter at interval, keep intake hoses sealed, use the specified oil grade and change it at the severe-duty interval. Fix overheating promptly, because heat softens ring tension.
Ring gaps must be measured in the liner the ring will actually run in, with the ring pushed square to a depth near the bottom of ring travel. Measuring in a different bore, or with the ring tilted, gives a reading that is wrong by enough to cause a failure. Use a feeler gauge set and record every gap for reference.
If a gap needs adjustment, file the ends square and deburr them before refitting. Never grind a ring by hand against a bench grinder, because the ends will not be parallel and the gap will open unevenly as the ring heats.
Browse the Weichai piston and components category, and pair the rings with the WP7 and WP8 piston 610800030035 or the WP7 and WP8 cylinder liner 610800010503.
One set covers one piston: two compression rings and one oil ring.
Only if the bore is within specification and shows a proper cross hatch.
Only if the measured gap requires adjustment.
Glazed bores, wrong gaps or rings fitted upside down.
EPID supplies diesel engine parts for Weichai, Baudouin, Yuchai, Caterpillar, Sinotruk, FAW Xichai and Cummins engines. Every order is checked against the original part number before packing, and our team can identify a part from a photo of the engine plate. Ask for a quotation with your model and quantity and we will reply within one working day.
