Valves, valve guides and valve seats work as a set. The valve seals the chamber, the guide keeps it running true, and the seat gives it something hard to close against. Wear in any one of them shows up as the same handful of symptoms — oil smoke on start-up, a lost compression reading, a tappet noise that will not adjust out — so the three are diagnosed and quoted together. This article explains what each part does, how to tell guide wear from seat wear, and what a machine shop needs to know before you order.
Valve, valve guide နှင့် valve seat သုံးမျိုးသည် တွဲဖက်၍ အလုပ်လုပ်သည်။ တစ်ခုပျက်ပါက ကျန်နှစ်ခုလည်း စစ်ဆေးရမည်။
In This Article (ဆောင်းပါးအကြောင်းအရာများ)
1. The three parts and what each does
2. Symptoms and which part they point to
3. Telling guide wear from seat wear
4. Intake and exhaust valves are not the same
5. What the machine shop needs from you
6. Fitting notes
7. How to order from Win Auto Parts
1. The Three Parts and What Each Does
အစိတ်အပိုင်း သုံးမျိုး
| Part | Job | Typical wear |
|---|---|---|
| Valve | Opens and closes the port; the exhaust valve also runs very hot and sheds its heat through the seat | Burnt or pitted face, worn stem, stretched or bent stem |
| Valve guide | Holds the stem square so the valve lands on the seat the same way every time | Bore wears oval, usually worst at the ends — the valve then rocks |
| Valve seat | The hard ring the valve closes against, and the path heat takes out of the valve | Recession into the head, pitting, or cracking between seats |
| Valve stem seal | Meters oil down the stem — supplied in gasket sets | Hardens with heat and stops sealing |
| မြန်မာ | Valve, guide, seat နှင့် stem seal | တစ်ခုချင်းစီ မတူညီသော ပျက်စီးပုံ ရှိသည် |
2. Symptoms and Which Part They Point To
လက္ခဏာများနှင့် အကြောင်းရင်း
| Symptom | Points to | |
|---|---|---|
| Blue smoke on start-up that clears after a few seconds | Valve stem seals, or worn guides letting oil drain down overnight | |
| Blue smoke on overrun, going downhill off the throttle | Worn guides — high inlet vacuum pulls oil past the stem | |
| One cylinder low on compression, no improvement with oil in the bore | A valve not sealing — seat or valve face, not rings | |
| Tappet noise that returns soon after adjustment | Seat recession — the valve is sinking into the head and closing the clearance | |
| Popping back through the intake or exhaust | A burnt or held-open valve on that cylinder | |
| Rough idle that improves under load | A partly sealing valve | |
| မြန်မာ | စက်နိုးစ မီးခိုးပြာ — stem seal သို့မဟုတ် guide | Compression နည်းပါက valve မပိတ်နိုင်ခြင်း |
The oil-in-the-bore test separates rings from valves
Squirt a little oil into a low cylinder and test compression again. If the reading rises, the rings are at fault. If it does not, the leak is past a valve. It takes two minutes and it decides whether the head comes off or the engine comes out.
Cylinder ထဲ ဆီအနည်းငယ် ထည့်၍ compression ပြန်တိုင်းပါ — တက်လာပါက ring, မတက်ပါက valve ဖြစ်သည်။
3. Telling Guide Wear from Seat Wear
Guide နှင့် Seat ပျက်စီးမှု ခွဲခြားနည်း
- Rock the valve in the guide with the valve lifted a few millimetres off the seat. Side-to-side movement at the head of the valve is guide wear.
- Measure stem to guide clearance with a bore gauge and a micrometer where accuracy matters; the limits are small and feel is not reliable.
- Look at the seat width and position. A wide, sunken seat means recession. A narrow, pitted band means the seat needs cutting.
- Check installed valve height against the specification. A valve sitting too deep means the seat has receded and the head needs new seats, not just a grind.
- Look at the wear pattern on the valve face — an uneven band around the face indicates the valve has not been landing squarely, which is the guide.
- Replace guides before cutting seats. Seats are cut using the guide to centre the tool; cutting first and replacing the guide afterwards undoes the work.
Guide အရင် လဲပြီးမှ seat ကို ခုတ်ပါ — seat ကို guide အတိုင်း ချိန်၍ ခုတ်ရသည်။
4. Intake and Exhaust Valves Are Not the Same
Intake နှင့် Exhaust Valve မတူညီပါ
| Intake valve | Exhaust valve | |
|---|---|---|
| Head diameter | Usually the larger of the two | Usually smaller |
| Temperature | Cooled by the incoming charge | Runs far hotter — often the hottest part of the engine |
| Material | Ordinary valve steel is adequate | Heat-resisting alloy, sometimes sodium-filled or with a hardened tip |
| Failure mode | Wear and deposits | Burning, stretching and cracking |
| Do not substitute | Fitting an intake valve in an exhaust port will fail quickly | — |
| မြန်မာ | အဝင် valve — ကြီးသည်၊ အေးသည် | အထွက် valve — အပူခံ သတ္တုဖြင့် ပြုလုပ်ထားသည် |
5. What the Machine Shop Needs from You
စက်ရုံသို့ ပေးရမည့် အချက်အလက်
- Engine code, not the vehicle model.
- Stem diameter and valve length, measured with a micrometer.
- Head diameter of both intake and exhaust valves.
- Guide outside diameter and length, and whether it is a plain guide or has a flange or circlip groove.
- Whether the head has been skimmed before — it affects installed height and valve timing.
- Whether you need standard or oversize guides; oversize guides are used when the head bore has been reamed.
Engine code, stem အချင်း, valve အရှည်နှင့် guide အချင်းကို တိုင်းတာ၍ ပေးပါ။
6. Fitting Notes
တပ်ဆင်ရာတွင် သတိပြုရန်
- Guides are an interference fit. They are fitted with heat and a driver, to the correct depth — not hammered in cold to an arbitrary depth.
- Ream or hone the new guide to final size after fitting; it closes as it is pressed in.
- Cut the seats after the guides are in, then lap and check the seal with a pencil line or a light test.
- Always fit new valve stem seals. They cost very little and they are the usual reason a head is taken off again.
- Check installed valve height and spring free length after seat cutting; a valve that sits deeper changes spring installed height and reduces seat pressure.
- Recheck valve clearances after the first heat cycle on engines with mechanical adjustment.
Guide အသစ်ကို အပူပေး၍ တပ်ပြီး ream လုပ်ပါ။ Stem seal အသစ်ကို မဖြစ်မနေ လဲပါ။
7. How to Order from Win Auto Parts
Win Auto Parts မှ မှာယူနည်း
Win Auto Parts stocks engine valves, valve guides and valve seats for the Japanese and commercial engines common in Myanmar, and can supply them alongside the matching gasket set.
- Call 09 5105768 with the engine code and the measurements from section 5.
- Say whether you need intake, exhaust or both, and how many of each.
- Ask for the gasket set and valve stem seals at the same time — the head is already off.
- Or email support@winautoparts.com with photographs of the old valves laid out in order.
- Or browse the engine range at winautoparts.com.
Engine code နှင့် အတိုင်းအတာများဖြင့် 09 5105768 သို့ ဆက်သွယ်ပါ။ Gasket set ကိုပါ တစ်ပါတည်း မှာပါ။
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