In Reply to: 8N missing under load posted by Tom8n396936 on June 16, 2017 at 12:20:28:
When any engine is overloaded, it will drag the RPM down and start running rich. The longer it runs like that before load is removed, the more fouled the plugs will get. It can take a while (or never) to clear fouled plugs. The hotter Autolite 437s will usually clear out and run right. A properly tuned engine will pull more load, and recover faster. As Bruce pointed out, even a fresh rebuilt engine won't pull load if it isn't properly tuned.