Lycoming Rocker arm differences ?
Peter Trost
out which rocker arm is the exhaust and which is the intake. These were
rebuilt by aircraft specialties and came back wrapped up in plain
paper. I can't find any markings that correspond to lycoming part
numbers. They are almost the same except that one type has an oil
passage drilled from the push rod to the rocker bearing, and the other
type only has a hole drilled from the topside of the rocker to the
inside of the bearing. Anyone know which is which ?
Thanks,
Peter Trost
Whunicut
put an engine together without some kind of guide.
The exhaust valve rocker arm is part # 74636. Bushing is 74637. The one that
has the oil hole drilled from the topside in to the bearing is the exhaust
rocker. That hole is supposed to squirt oil onto the valve stem and spring and
*hopefully* cool them. ;/))
The intake rocker is # 69444
Hope this helps,
Warren
Peter Trost
I have both the Overhaul manuel and O-320 parts manual. The parts manual is shows
the part numbers, but the diagrams are not detailed enough to identify these parts.
The casted in part numbers on the rocker arms are not at all legible. I figured
that the hole on the valve side was to dribble oil on to valve stem, but examining
the part, it looks like this is the only hole into the bearing. The intake looks
like it gets oil to the bearing from the pushrods. The pushrod end on what appears
to be the exhaust rocker has no oil passage. This doesn't make a lot of sense after
examining things.
Peter
Whunicut
>shows
>the part numbers, but the diagrams are not detailed enough to identify these
>parts.
Peter, in your parts cat. Figure 3-4, parts # 2 and 4. On the left page is a
list and explanation of parts.
>The casted in part numbers on the rocker arms are not at all legible. I
>figured
>that the hole on the valve side was to dribble oil on to valve stem, but
>examining
>the part, it looks like this is the only hole into the bearing. The intake
>looks
>like it gets oil to the bearing from the pushrods. The pushrod end on what
>appears
>to be the exhaust rocker has no oil passage. This doesn't make a lot of sense
>after
>
>examining things.
>
>Peter
*********************************
No, it doesn`t make any sense. I suspect the rockers somehow slipped by
inspection at the factory and are some that did not get through the complete
machining cycle.
The rockers must have a hole in the push rod end because this is where oil is
fed in to the bushings.
Hope this helps,
Warren
Peter Trost
Whunicut wrote:
> *********************************
> No, it doesn`t make any sense. I suspect the rockers somehow slipped by
> inspection at the factory and are some that did not get through the complete
> machining cycle.
> The rockers must have a hole in the push rod end because this is where oil is
> fed in to the bushings.
>
> Hope this helps,
> Warren
Warren,
Upon further inspection, ( i.e. blowing air through the oil passages ) the exhaust
rocker has a passage from the pushrod to the bearing and then on to the hole that
dribbles oil on the valve. However, the intake has no passage from the pushrod at
all and all there is is a hole just under the arm that engages the pushrod
(topside) that goes through to the bearing. There is a oil passage here, but it is
a drip system and not in the oil system directly. I guess that the oil just leaks
out of the pushrod cup and dribbles down the lifter and into the hole that goes
into the bearing.
Excuse me while I go rinse the oil out of my mouth now.
Peter