THe 2.5L engine (9.3 : 1 CR. S2 cam, triple 40DCOEs, 4yrs/ 20,000 miles since
rebuilding, lightly radiused edges on head after milling ) in my 71 GT-6 is
dieseling. For the first 10,000 miles I was able to use reg unleaded (87
Octane). When the engine began to diesel (too much, about 1.5 years ago) I
switched to mid grade unleaded (89 octane). Now it diesels too much on mid
grade. I backed off the timing to 10 deg. BTDC (was running at 12 deg BTDC) and
this improved the situation for a few months. I prefer not to use ($$) premium
Could the dieseling be caused by carbon build up? If so, what is the
appropriate quantity of water to spray down the carb throats? I am thinking of
using a spray bottle (such as window cleaner comes in). If this is an
appropriate water applicator - how many squirts / unit of time / cylinder? I
have never tried to do such a thing.
Another question in the same vein. Sometimes (maybe once in 100 times) when
shutting off the engine, it runs in REVERSE direction or a second or so. Why?