Tom,
There is a special tool for removing the valve springs while
they the engine is in place.
While you can find universal OHC tools, usually they are too
large around the valve keeper and hit the side of the cam tower.
The tool I have, sold by Nissan, for the L series engine needed
a little clearance grinding to clear the cam towers on the U20.
Only comment is to stuff a rag down into the front of the engine,
by the chain. Also something to block the rear oil drain hole. Toss
a shop rag around the top of the valve as the keepers like to "pop"
off and go flying once broken loose.
The rope trick is a good one. For the rest of the list that is
when you feed in some 3/8" rope into the cylinder, then rotate
the piston up so the rope is between the valve and top of the piston.
Keeps the valve from dropping into the cylinder.
One problem I have had with air pressure, if you are not exactly
at TDC the piston will move downward. I've had wheels climb over
a 4x4 with ease from the torque of the air pressure! Takes a
little practice to get the piston right at TDC!
I've had luck with replacing the valve stem seals to keep from
sucking in the oil in pass the valve guides. If the guides are
worn (100K miles) then regard this as a temporary fix. Then again
I only drove the roadster 3K miles a year, so sometimes those
fixes will be fine for quite a few years.
Oh, you only need to replace the four seals (intake) as oil
leakage is not a problem with exhaust valves.
Cheers,
Tom Walter
Austin, TX.
Tomet9@aol.com wrote:
> Hi list,
>
> I've finally got enough courage up to replace my valve seals on a U20. I do
> not have a air compressor and so some have suggested doing the old rope in
> cylinder trick to do the replacement. Would I have to create any special tool
> for the job to relieve the keepers on the stem ends? Does anyone have
> experience along this line? Any precautions I should know about? I just hate
> to take the head off and seals are cheap. If any one out there can give me a
> few tips I'd appreciate it.
>
> Thanks,
> Tom Prather 69/U20 lady in red
>
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