supercub

What symptoms really, truly, absolutely warrant valve adjustment on the 3zve? To me this seems to really be the questions, not what is recommended as per the FSM or what is considered to be a "good idea".

As it seems often to be the case w/ this engine, I have oil leaks from the valve covers/ cam plug/caps. It seems prudent to adjust the valves since they are exposed during the leak repair process. But... from what I have gathered from reading up on the valve adjustment process it is a huge pain that is more often than not, unnecessary.

Of course if the clearances are way out of spec, then adjustments needs to be made. But is there some fudge factor outside of the factory spec that justifies leaving things alone? Also, lets say if the clearances is ok, are there any other symptoms that would justify/ require the adjustment (idle issues, roughness, fuel economy, noises, etc)?

While being an active and licensed airplane mechanic, OHCs, adjustment shims, and cars in general are a new experience for me and I don't want screw up something major, as the whole point of doing the work my self is to save money (and learn how to work on my truck for fun).

My rig has about 190k and runs great. But I am the 3rd owner and I have no idea if any attention has been payed to the valves during the engine's life. I just figure since I'm gonna go to all the trouble to try and stop the leaks, might as well do the valves, but only if it is really necessary.

Thanks for any advice.

mt_goat

I guess a compression test would tell you if they were badly out of adjustment.

abecedarian

There are no 'symptoms' of valves being out of adjustment- just about any performance issues caused by mal-adjusted valves could just as easily be attributed to ignition, induction or exhaust problems.
What may cause one pause for thought about the valves are engine performance issues that have had everything else BUT the valves checked: no one wants to take the engine apart.
The valve-train is a mechanical wear system. They do wear and need to be checked periodically even when nothing else seems to be wrong. It is a gradual wear process and as such, do not receive the attention they should get until it's too late.
I'd say check the valve clearance at least every 40,000-50,000 miles... and also anytime anything significant (more than an oil/fuel filter, pcv valve, or tune-up/spark plug change) is done to the engine.

To wrap it up, the only symptom that requires a valve adjustment be performed is that the valve adjustments are out of spec.
The important thing is to check them periodically.

Targetnut

Loose valves are noisey
Tight valves cause rough idle and can lead to burnt valves.

If you have it apart to reseal the valve covers you should absolutely check the clearances.

If the clearances are in spec, there is no other reason to adjust them