Rocker cover oilways

[PX207]

Afternoon all,

Whilst my cylinder head is with Ken De Groome it's given me a chance to get some other things done on my G3LS. Having looked at the oil circulation diagram in the maintenance manual I believe there at meant to be 2 oil ways behind the tappets (highlighted). As can be seen by the photos below of my rocker cover the seem to have been blocked!

[Duncan]

They may be the type of metering jet that has a small flat on one side, try passing some fluid or air past them to confirm.

[PX207]

They may be the type of metering jet that has a small flat on one side, try passing some fluid or air past them to confirm.

cheers Duncan

[jackstringer]

IIRC they are not blanked but baffled. They allow oil to ooze rather than just spurt everywhere. If you ever want to you can run the engine with the cover off and watch them things go up and down.

[56G80S]

I can't think why someone would do that! My concern would be that it was done to compensate for some other fault; the standard arrangement works fine. Jack is right about watching but in my case I cut the bottom out of a transparent food container, scissors only, punched the holes for the studs and watch all you like without the risk of oil shooting everywhere.

Johnny B

[jackstringer]

Its easy,



This was filmed on a very old camera.

[PX207]

Johnny B & Jack many thanks, once I get my head back I'll be sure to upload a little video of my own

[Les Howard]

That is a very weird. The 2x jets that are in all AMC cylinder heads appear to have been blanked off. Having the oil jets directly above the pushrod cups, ensured their lubrication and also damped some contact noise. The surplus then runs down to the push rod and down that to lubricate the cam follower tappets. Furthermore having a decent amount of oil being flung from the rocker arms meant some of it landed near or down the hole which is drilled through to the inlet valve guide, the amount being regulated by the screw. (see horizontal hole at the front just right of centre)... Restricting or removing this entire oiling route as just described can only result in an inferior lubrication of the engine. I show an image of the correct jets...Please note although they are known as jets, the amount of oil they pass is quite small and they never really squirt oil...just ooze which is sufficient.

Rockers.jpg

[mdt-son]

PX207, 56G80S, and Les, I suggest you read the thread "Oil metering hole size" in the Public Forum/Help group. There was a changover for 1954 models apparently, aimed at increasing the oil flow to the rocker arm bushings and to the pool at the exhaust valve guide, at the expense of the pushrod cup lubrication.

I just received a rocker box with previous jets behind the rocker arms blanked off, identical to the one shown in the picture above. It is essential to know the orifices are not truly blanked off, they are minimized. Having examined the blanks under a magnifying glass, it's hard (well, impossible) to detect the small flat Duncan refers to (width is 0.3mm apparently). How does one preserve this feed from contamination and clogging up? Any oil feed should be large enough to use some thin wire (e.g., as used for cleaning carburettors) to poke through, me thinks.

The 1963/4 spares list mentions 3 metering jets (018890). An obsolete entry? And where is the third - should there be one for the oil pool? My rocker box has a very thin bore at this location, no metering jet.

- Knut

[56G80S]

Knut

Was that change for 1954 models only? When I bought my 1956 G80S in mid 1970's it was very original in every other way. Perhaps it had an earlier rocker box fitted but mine has "jets" and were I to run without the tappet cover on oil would come out of the rocker box. I've not experienced undue wear on the rocker arm bushes. I replaced these a long time and many 1000's of miles ago and they're fine.

I don't see how plugging these jets would increase oil in the pool feeding the exhaust valve as it's not a pressure feed.

Johnny B