valve adjustment

[budgerian]

What is the reason the valves need to be adjusted in sequence (1-5-3-6-2-4). Is it just because it's easiest that way as they'll be sequentially closest to the point where one should adjust them, or is their another reason?

Second, if one exhaust valve eccentric is near the end of it's adjustment range, what could be the cause?
Has anybody ever experienced a problem with one of the eccentrics, causing the above?
I'm asking because eveything on the head looks to be in great shape, no strange wear on the cam, oil getting everywhere and compression was near perfect as well.

Also, how would the engine run when one exhaust valve is a bit too loose for comfort (I managed 0.30 just, but I won't be able to adjust it any more next time.) I would assume better to loose than too tight, but look forward to hearing your opinions.

Roger

 

[MMercury]

What is the reason the valves need to be adjusted in sequence (1-5-3-6-2-4). Is it just because it's easiest that way as they'll be sequentially closest to the point where one should adjust them, or is their another reason?

Second, if one exhaust valve eccentric is near the end of it's adjustment range, what could be the cause?
Has anybody ever experienced a problem with one of the eccentrics, causing the above?
I'm asking because eveything on the head looks to be in great shape, no strange wear on the cam, oil getting everywhere and compression was near perfect as well.

Also, how would the engine run when one exhaust valve is a bit too loose for comfort (I managed 0.30 just, but I won't be able to adjust it any more next time.) I would assume better to loose than too tight, but look forward to hearing your opinions.
Roger

You answered your own question regarding the suggested valve adjustment sequence. It is presumptively simpler to do it in some sort of order. Nevertheless, you can do it in any order you please as long as the bottom of the cam lobes are at their furthest point from the rocker (in other words - with the valves closed you want to make sure the subject cam lobe is positioned to least affect the rocker). Aftermarket cams may require different methodology depending upon the cam design. This is fairly basic and I would suggest you search any number of texts that cover tuneups and engine maintenance.

Eccentric wear can be common. Rocker bushings do wear and valve stems are occasionally mushroomed, lightly ground or worn too. And - cam lobes have a tendency to wear, especially if they receive inadequate lubrication. This issue has been addressed with the used of oversized eccentrics. Oversized eccentrics used to be available at dealers and the usual part suppliers. Machine shops that worked on M30 engines might also keep a few around for obvious reasons. I would think you could make your own with a little welding and grinding but if the repair were to last, the metal would have to be heat treated and possibly nitrided. Other engine designs surmount the problem with shims typically placed above the valve, but I cannot recall seeing this done with an M30 Single overhead cam engine.

If I had to err on the side of caution for a questionable valve adjustment, it would be toward a "looser" adjustment. Valves must be cooled in order to prevent burning or warping. Cooling may occur via the incoming fuel/air mixture but the majority of the heat transfer is said to occur via the valve contacting the valve seat/cylinder head. A tightly adjusted valve (with little clearance) has less time in contact with a valve seat than a loosely adjusted valve. If you have a rich mixture or water injection on your engine used predominantly for drag racing - this may be a non issue.

I couldn't say how your engine would run if one or more valves were adjusted with far more clearance than designed. Altering valve clearance can affect both valve lift and duration of time open. There are exceptions to this rule, yet reducing lift and/or duration generally has negative consequences for engine efficiency.

Good luck!