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As part of the original engine design, an oil trough was mounted above the lower timing gear to direct oil specifically to the timing gear set.  This trough was discontinued in 1956 with the thought process being that the excess oil from the right side rocker arm assembly still being adequate oil for the timing chain area.  Here’s a link showing the oil trough.

Timing chain oil trough 

If completely pressurizing the rocker shafts, then here’s a link showing what Tim McMaster has come up with to provide some additional oil to the lower gear and chain.  This helps to replace the oil that is no longer coming down the original path.

Pressurized timing chain oiling

Any engine modifications that do away with the additional oiling at the timing set will simply accelerate timing chain wear.  The link style timing chain used in the original engines is more susceptible to wear than the roller types of chains so this is something to keep in mind.  Although there is some oil seepage coming from the front cam bearing during normal running, it’s questionable if that’s enough oil to adequately lube the original ‘wide’ link timing chain that’s being used without using some of the oil that comes from the topend of the engine.

The original oiling system when used with modern oils does actually hold up well over the long haul.  Most of the problems with the early engines in regards to lubrication issues centered around the use of paraffin based oils (big no-no in the Y’s) or inadequate oil change intervals or both.  My own 272 has over a quarter of a million miles and it’s still std/std on the crankshaft with the rest of the engine only showing minimal wear.  This engine has been using TropArctic 10W-40 since 1955 and based solely on this, says a lot about the advantages of modern oils.  TropArctic has been around since 1954 and was actually the first multi-viscosity oil introduced for automobile use.

And here’s the link to a thread with links to several past threads talking about pressurized rocker arm shafts.  http://www.y-blocksforever.com/forums/Topic51052-3-1.aspx 

Doing a search on the site will bring up some more. 

I just recently did a rebuilt on my 312 with all new parts (cam, rocker arms etc.) with no modifications to the oiling system.  While still on the engine engine stan I rigged me a drive to go down into the oil pump with the distributor removed so I could turn the pump to prelube the engine.  I was going to use an electric drill to turn the pump but decided to just put a wrench on the shaft I had rigged up first.  After the oil picked up and filled the oil filter and rocker arms shafts, there was a full volume flow of oil from each overflow tube at the end the rocker arm shafts and that was just turning the pump by hand.  Based on the experience I had with the Y block back in the early 1960's, I never had a problem with oiling to the rocker arm shafts after I rebuilt the engine and cleaned all the oil passage ways and kept the oil change regularly.  That was just my experience.     

Pressurizing the rockers will slow the oil flow in the head resulting in the oil collecting extra heat, especially where it makes the turn in the head, if it bakes there could plug up oil flow in that area.

When in doubt about zinc/phosphorus levels in a particular oil, just read the API oil bulletins to verify exactly which oils have the reduced phosphate amounts.  But as a general rule, the reduced phosphate oils are only those oils being used by the new car manufacturers.  Any oil with 40 or higher in the weight labeling is exempt from the reduced zinc/phosphate mandate as none of these oils are being used by the oem’s in the new cars.  Visiting the oil manufacturers website and bringing up the MSDS sheet for a particular oil will most of the time give you the zinc/phosphate amounts in that particular oil.