Tappet Clearances?

[Log Skidder]

I just started fiddling with the IXK3 engine on my HG-68.  I just bought a hand crank assembly, a gasket set, and a new intake/exhaust manifold from Zimmerman's Oliver Cletrac.  

Previous to this fiddling I haven't run the crawler in a couple years.

I changed the plugs.  Cylinders 1, 2, and 3 looked like they had dry deposits.  They looked good though.  The "deposits" are a light brownish grey.  I think this many have been from a fuel additive.  Spark plug number 4 was wet/greasy the way an oil burning or rich burning fouled plug would look.  

But then it gets interesting.  I take the valve cover off and was happy to see everything well lubricated.  I watched the tappets as I slowly turned the engine over.  Most of them looked like they had close contact with the valves, except for cylinder 4.  Cylinder 4 looked like there was 1/8" or more as a gap.  The tappets would barely touch the valves stems.  It appeared that there was barely any screw thread exposed on the intake and exhaust tappets for that cylinder compared to the amount on the other cylinders.  I think all that needs to be done is to adjust them properly and my fouled plug problem might go away.  Might have more power too.  

I see in the service manual that the hot intake tappet clearnace is .006 and the hot exhaust tappet clearance is .008.  But what would be a good number to use for a cold engine before you have it warmed up?

[thecatskinner]

Based on an estimated total length of 6" for the valve stem and tappet and a 150 F temperature differential add 0.006" to the hot settings.

(You still need to set hot)

[Log Skidder]

Thanks Catskinner for the recommendation.  

Any idea why someone might intentionally set a tappet as low as it would go?  Almost like they were trying to turn off the cylinder...  Just curious.  

Also I noticed that the tappets seem to rotate about a quarter turn each time they move.  Seems to be mostly in one direction.  (i.e. four valve actuations and they are almost around one turn)  Are they supposed to do this?  Is it an indication of wear?

[thecatskinner]

The tappets should rotate--that is to avoid wearing a groove in the bottom of the tappet.

As to why--I haven't a clue;)

Are the lock nuts tight?

I have seen enough "shade tree adjustments" over the years to understand I don't understand:o:D:D

[Log Skidder]

The locknut and screw were loose on the 4th cylinder.  I brought them up to .012" intake and .014" exhaust.  

I found that some of the other ones were looser than that.  

Now I am on the hunt for one of those old style spring compressors so I can regrind the valves.  I remember seeing them at the parts store long ago, now they have new-fangled ones specifically for GM V-8 engines.  Basically a bracket that you mount to a V-8 head in place of a rocker.  

I still have to play with the valves and get some replacement parts for the magneto.  And paint teh intake/exhaust manifold, etc.  Getting closer to that first firing.  I am wondering if the whole time I was using the crawler a long time ago if that one cylinder had badly adjusted tappets, or if the reason I stopped using the crawler was because it started sounding bad and running poorly due to the tappets.  Anyway, it should be better now.