Sounds are very difficult to describe on the written page or verbally. To one
person it might be a tap, to another it might be a thump, and on and on.
If the engine has a good many miles on it the main bearings are probably worn
and you will hear a dull thump when you first start the engine because the
crankshaft isn't yet supported by the oil pressure. This usually quiets down after
the engine starts and the oil pressure starts to show on the gauge.
There are ways to isolate a loose connecting rod (rod knock) but I would agree
that the best way to isolate where your noise is coming from is with a
stethoscope. This discussion on engine noise is very well done and may help you
. But as is pointed oout even for an experienced mechanic engine noise can be a
tough nut to crack.
http://www.supramania.com/forums/showthread.php?20486-Rod-Knock-Diagnosis-and-FAQ Unless the truck has had someone that took good care of it and gave it all the
required maintenance over the years you most likely have bad motor mounts
. This usually results in the engine sitting unsupported on the cross member
because the rubber has turned to jelly. That can transfer a lot of the engine noise
into the cab.
As far as setting the valve lash or adjusting the rockers or valve adjustment (all
the same ting) there are a number of instructions here on the ‘Bolt that describe
how to do it with the engine off once it is warmed up. Some people prefer to
adjust the valve lash with the engine running. That is a bit more difficult but it
assures that they are all adjusted at the same temperature. It could take fifteen
minutes to a half hour to adjust them and with the engine off that’s enough time
for the last valve to cool down a lot more than the first one.
Properly adjusted, a valve train with solid lifters will have some high-pitched
metallic sound similar mama’s sewing machine.
Don’t rush into tearing your engine down if it’s got good oil pressure and running
ok. These old Stovebolts will run for a long time even after they are well worn. To
cure your oil burning your only option is to have the engine rebuilt, which will
run you somewhere around 3k.
Denny Graham
Somewhere north of Sandwich, IL
