Pressed steel rocker - How it oils the pushrod and valve tip

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stevelemoir
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Pressed steel rocker - How it oils the pushrod and valve tip

Postby stevelemoir » Fri Mar 20, 2020 5:56 pm

I did a total engine rebuild last year but didn't do anything to the rocker assembly.
After running the engine for 20 miles I noticed that the valve tips and rocker contact pads of valves 7 and 8 were dry of oil.
All other valve tips had loads of oil as did all 8 pushrods tops.

This got me trying to work out how the valve tips and pushrods get oiled.

The pushrods are easy because of the oil way through the adjuster to the opening in the
central pivot bush.

The valve tips are more difficult so I wanted to check out where oil was released from the rocker.
Firstly I tried pumping oil through but couldn't get enough pressure.
So I decided to pump air through. To do this I cut up an old push bike tyre valve and used some washers one side of the central pivot and another bit of rubber tyre tube and a two pence coin for the other side. This picture shows the equipment used:
The equipment required.png
The equipment required.png (57.44 KiB) Viewed 324 times
This was secured using two pairs of mole grips:
Secure with mole grips.png
Secure with mole grips.png (71.98 KiB) Viewed 324 times
This was attached to a foot pump:
The set up.png
The set up.png (47.11 KiB) Viewed 324 times
The rocker was put under water and air pumped through.
(This picture is not very good because it was taken from a video file.)
This clearly showed air only coming from the adjuster end but from two places:
1. From the end of the adjuster which impacts the pushrod
2. From the tiny hole under the adjuster nut
Bubbles2.JPG
Bubbles2.JPG (34.18 KiB) Viewed 324 times
So my conclusion from this is that some oil comes out of the tiny hole under the adjuster nut and travels down the groove in the top of the rocker to the valve end and works down to lubricate the contact pad and the valve tip.
Rocker.JPG
Rocker.JPG (71.24 KiB) Viewed 324 times
Am I right in my conclusion or do the valve tips get oiled some other way...by oil splash for example.

Any other theories?

philthehill
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Re: Pressed steel rocker - How it oils the pushrod and valve tip

Postby philthehill » Fri Mar 20, 2020 7:38 pm

Your flow chart is correct except for the flow of oil to the hammer tip.

Examining pressed steel rocker Pt No: 2A964.

1. Oil from the rocker shaft goes via the drilling in the rocker to the waisted rocker adjusting screw. Early rocker adjusting screws were drilled from the waist to the ball. Important Note: The drilling from the waist to the ball and the waist was discontinued on later rockers as the adjusting screw had a tendency to break off at the waist. If you have drilled and waisted adjusting screws they should be replaced with the later solid/non drilled/non waisted screws. I always replace any waisted and drilled screws I come across with the later type.

2. There is no designated oil feed to the rocker tip from the waisted and non waisted adjusting screws end of the rocker but there is a forming between the two sides of the pressed steel rocker which along oil may creep from a waisted adjusting screw and exit at the hammer end of the rocker through the very small fold on the inner side of the hammer.

Because the oil transfer holes are small they can easily get blocked with crud.

Later rockers had a oil exit hole in the rocker pivot boss which sprayed oil around.

There should be enough oil being thrown around inside the rocker shaft to lubricate everything.

You do not need excessive oil around the top of the valve stem as it can get past the valve stem/guide and make for smoky running.

BMC made several modifications/revisions to the rocker and adjusting screw to increase its strength and reduce the amount of oil being thrown around near the valve stem.

If the adjustment threads in the early rockers are filled with crud and stop the adjusting screw moving freely - the threads can be cleaned through with an appropriate size cycle thread tap which does not cut metal but does get rid of the crap.



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