Valve Seals

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Valve stem seals. Datsun 1200 originally use an umbrella type fitted to the intake valves only. Later A-series engines moved to a Lip-seal type that fits over the valve guide (positive seal) and were fitted to all valves.

Overview

B110 used umbrella seals on intake valves only. B210 used positive seals on all eight valves.

Aftermarket seals come in various types, as this MGB graphic shows:
photo

diymark: I used the positive type seals on the inlet so oil doesn't get sucked in under vacuum and the umbrella type ones on the exhaust as the extra oil allows better lubrication and cooling of the exhaust valve.

The O-ring is an original A-series item. The later spec is the positive seal (fits on the guide).

ddgonzal: I like the umbrella seals best -- they just fit on the stem, not on the guide. Umbrella seals shield the valve stem from getting oil in the first place, so keep oil from going down the guide. For racing where the heads rebuilt regularly either will be fine. For new heads, Nissan chose to use the positive seal.

If it's totally white and disapates into the air, it is water vapor. If it is white with a tinge of blue that blows away, but doesn't evaporate into the air, it is burnt oil, yes probably from the valve seals. Sometimes just replacing the seals will help (and you do not need to remove the head). But replacing the valve guides is usually needed to clear it up 100%.

Diagnosis

Also see Smoke

Symptoms of bad valve seals include 1) Puff of bluish smoke on starting the engine. But no smoke when revving the engine.

• worn or cracked valve guides
• incorrect size valve stem seals (not tight enough around the valve stem)
• Hard and brittle valve seals
• Torn valve seals
• Improperly installed valve seals

Remove the Rocker Cover and use a flashlight to look between the valve spring coils. If you see torn or missing seals, time to replace them. Or if you see one or two that have popped up off the guide, time to replace them.

Do a Wet Compression Test to verify that the rings are still good. Otherwise, no valve seals won't fix the smoking problem.

The valve stem seals go bad due to:

• Heat causes them to get brittle and break
• Heat causes them to get hard and so stop sealing well
• Tearing or other physical damage sometimes occurs

Valve seals don't dry out as they are surrounded by oil, but Positive Seal types can get brittle and thus stop sealing correctly. Umbrella seals generally keep working when they get brittle.

In a good engine, oil covers the valve stem. The seal keeps it out of the guide. With old seals, there is no seeping, but oil runs down the valve through tiny gaps in the seal.

Replacement

1. Compress the valve springs and remove the keepers, then the springs
2. Remove old seals and put new seals on
3. Re-fit the valve springs

Remove Valve Springs

Cylinder Head Off

Template:Valve Compressor Traditional

Cylinder Head On

You can replace the valve stem seals without removing the cylinder head. It's far more work to remove the head.

The valve springs be replaced without pressurising cylinder. You can change the valve springs without taking the head off, without using air pressure. I have used the following methods:
1. Clean rubber hose fitted into the cylinder
2. Clean thin rope pushed into cylinder
Then rotate the piston up, and it holds the valve from dropping

Method 1: Rope Trick
Remove all spark plugs and turn the cylinder until distributor rotor is pointing somewhat before the plug. Then feed in clean 1/4" (5mm) rope until the cylinder is filled. You can also use clean new vinyl hose. Then rotate the engine the rest of the way. The rope will hold the valve from dropping when you undo the spring.

Method 2: Compressed Air
By pumping the cylinder full of air with piston at TDC. I got an old spark plug, and busted the ceramic part out, and then braised in a fitting that is the same as the tire valve stem.

If you use air you need to have the piston at top dead center otherwise it will try and turn the engine. 10 psi is all that is needed to hold the valves up. A Leakdown Tester is an ideal tool for adjusting the air pressure.

Spring Compressor
Use a fork type or bar type or an On-Engine Valve spring compressor.

On-Engine Valve Spring Compressor

If it's still on the engine, you can do what I always do:

1. remove spark plugs
2. feed clean small-diameter soft tubing
3. turn crank until piston stops
4. change the seals
5. repeat next cylinder

The tubing inside the cylinder holds the valves from falling down.

With head on engine, take out spark plug, rotate to TDC for that cylinder, insert clean rubber tubing, as much as will fit. This will hold the valve in place. Remove rockers from shaft (on some engines, you can leave them on). Use a forked bar with a hole in it to push the spring down, remove the keepers, replace the valve seal (and spring, if that's your goal), then put it back together. The bar I have is basically flat stock turned up on the sides for strength. It's a simple device.

Part Numbers

A-series valve seals (positive seal type) are the same as the Nissan SD25 engine.

Aftermarket

• Fel-Pro SS27283
• Beck/Arnley 0221446
• Sealed Power MV1796 (Umbrella type)
  • Upper Inside Diameter: 0.315
  • Overall Length: 0.718
  • Inside Length: 0.625
  • Seal Outside Diameter: 0.89
  • Type: SS

B110

• 13207-18000 SEAL-OIL VALVE (INTAKE ONLY) 8 A12 -672 2 $1.11
• 13207-H2301 SEAL-LIP VALVE OIL (INTAKE ONLY,KEEPER) 4 OP A12
• 13207-H2310 SEAL-LIP,VALVE,OIL (INTAKE ONLY,NOK) 4 OP A12 - $4.62

B310 - positive seal type

• 13207-H7200 SEAL-OIL VALVE (8)
• 13207-H7210 SEAL-OIL VALVE (8)

L-series

L20B

• 13207-21002 SEAL-OIL,VALVE
  • Upper Inside Diameter: 0.27
  • Overall Length: 0.56
  • Inside Length: 0.35
  • Seal Outside Diameter: 0.64
  • Type: TP

The lip-seal type is different for A-series and L-series. This is the type that fits over the valve guide. It is the "normal" type for L20B, is the same as Chevy 4, Isuzu, KA, VG and L-series.