OK, set my lash yesterday, and put in new plugs while I was at it. Installed valve covers and let gasket shellac dry overnight.
Now, the performance test today. Well.....darn, I can't tell for sure if there was an improvement or not BECAUSE when I removed the plugs, I found a badly fouled one. More on this below (sidenote). However I am sure the plug did fire under light load, so I can say (without 100% confidence):
1/ With the tighter lash (Crane correct lash), the idle dropped. I had to turn both carb idle stop screws in a little over 1/4 turn. Best guess for this was tightening lash increased valve overlap.
2/ Low rpm power seemed snappier, but this could also have been from changing plugs. But I do believe it helped as the cam should appear more "advanced" with a tighter lash.
3/ It seems a little bit quieter (as one would expect) but hard to tell over the exhaust, even while cruising.
4/ high rpm was always great and I admit to never taking advantage of all the power available, so no difference there that I can see, but that's due to my driving style.
Sidenote:
Seeing that 1 bad plug was worriesome. I knew the engine doesn't smoke, so that was in my favour. I did a compression test and a leak-down test, and compared it to another cylinder. Identical readings. Compression test was wacky (as in very high)....after I rebuilt this engine in the spring, I got 195 psi. Now I am getting 220 psi. Must be due to rings wearing in, although I can't remember for sure if I held the throttle open during the first compression test last spring. I also checked valve rise and fall and found everyting OK in that regard.
I had an internal carb leak on the rear carb, which I recently fixed. Before I fixed it,. back four cylinders were running richer than the front four as indicated by reading the plugs. So it's possible this plug fouled due to the carb leak, and couldn't clean itself after I fixed the carb, while the others did.
But, even though I say I checked them, the truth is I never did check #4 cylinder as the plug is a bit tricky to remove/install due to the close proximity of the battery. Actually, it's getting the plug wire back on securely that's the difficulty....dont' laugh until you try it! So, the plug could have been damaged by the crossfire I was having during the humid part of summer, although I can't see a crack in the porcelin. I did test the plug on my ancient AC Delco SparkPlug checker/cleaner and it failed miserably.
This plug was one of a set of RF11YCs I installed as no RF9YCs were in stock. I did acquire 8 RF9YCs the other day, but NAPA said there was none at the warehouse so manged to get me NOS from two of there other stores.
By the way, I think Champion quality is going down hill. Check these pics:
One of those two is not like the other......top one is constructed properly
Hard to see, but threads are deformed at bottom. Note how threads converge near side electrode. Came that way. I didn't notice until I tried to install it. I guarentee I didn't cross-thread it myself, as I always use my fingers to start plugs. Of course, maybe I had Wheaties for breakfast that day.....LOL.