The reason I ultimately took the head off this go round, was because my exhaust manifold was glowing red when I kept the engine under sustained load (up a hill 2-3000 rmp for 30 seconds or more). Because I've had this engine rebuilt essentially twice in the past 3 1/2 years, I'm perhaps being a little gun-shy and over critical.
The original rebuild I paid around $1700 for 3 1/2 years ago blew pistons 3 and 4 last summer. When it was all rebuilt this past september and put back together-running, the engine had a stumble, so I pulled the head off (again), and the rebuilder identified a bad exhaust valve. I ran it from october till about a month ago when I smelled what I thought was that 'too hot' paint smell on the engine doghouse (it's a 62 econoline with 200ci) so I popped the lid (still driving) and to my astonishment the exhaust was glowing red from the stock manifold clear down into the exhaust pipe where it turns (I have limited mechanical experience).
Thanks to all the help I received here, I have since this past summer installed a DS II and a Weber 32/36 and a new exhaust tip to tail. I have tried every possible combination of timing advance and carb jets, with no change in the exhaust's apparent temperature (though the engine runs great!) I have carefully checked the cam timing, fuel pressure, vacuum, vacuum advance, on and on.
So now with the head off (scare of burning more pistons), and the head in the hands of a new machinist (different shop, same parent company, still warranty work
) the machinist has recognized that the intake valves were not seating properly. He cannot positively determine if this was because the previous machinist was doing shoddy work, or if there is some other factor in the valve train geometry. There are no cracks in the head and the head thickness seems to be normal (I measued 2 heads, the one in question and a spare, both of which were about 2.430 thick measured from the deck surface to a head bolt surface).
So it seems like we're close to having identified darn near ever possible consideration (near as we can tell), and we have decided to go with an adjustable rocker arm assmbly to make up for any unknowns.... I figure therefroe we've ruled out everything except the cam (and I can't help but wonder if the previous rebuilder put an older non-hydrolic cam in with hydrolic lifters, and I wonder what that mismatch might do?).... sorry for the long story... trying to get this right before I have to have my credit limit extended again...... thanks for reading... David SoCal
