Ford used three methods to plug the hydraulic lifter passages. Two of these methods completely blocked oil flow, the third provided restricted flow to the lifter passages.
427 sideoiler and 427 topoiler blocks were all drilled for hydraulic lifters from 1968-on, in order that they be useable in production automobile applications. From this time on, all 427 service blocks seem to have gotten a solid plug installed into each of the two short "oil feeder passages" drilled between the top oil gallery and the two lifter galleries. This blocked oil flow to the lifters in 427 blocks, but these blocks could readily be converted into hydraulic lifter blocks just by reaching in from the rear of the block and prying these two soft steel 379898-S plugs out with the twist of a flatblade screwdriver and some elbow grease.
Here are three pics of the plug and two factory blueprints showing it installed:
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278812&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278813&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278814&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278810&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278811&original=1
A second method of plugging the top oiler passage was used in Ford's NASCAR program. Rather than installing two plugs, the later NASCAR blocks got a single brass plug installed at the front of the block which plugged the oil feed passage just before oil got to the top gallery. Naturally, this method did not work for topoiler 427s, since topilers used the top gallery to feed the cam and crank, too. Only sideoilers could be plugged with the single plug up front, since the top gallery on the sideoilers did not feed the cam bearings or crank, only the lifter passages, reference:
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278816&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278815&original=1
In the thrid method, Ford seems to have substituted the familiar "flutter valve" (a late version of the "jiggle pin") for those folk wishing to re-plug the hydraulic lifter passages in their 427 blocks.
A single "flutter valve" was frequently found on ordinaary Ford production blocks which contained hydraulic lifters. This valve would have been placed at the front of the top oil passage, behind the timing cover, the purpose apparently to quickly "burp" air out of the gallerys to speed oil flow into the lifters upon cold startups.
I'm not sure what the line of thinking was for installing a flutter valve into the 427, though three possibilities for selecting the flutter valve come to mind. First, the trickle flow provided by these valves might help lube whatever solid lifters were installed, except for the fact that oil flowed backwards through the flutter valve in this odd application, so it wouldn't have worked as intended in the original applications. A second possibility is the flutter valves were cheap and universally stocked at Ford, GM, and Chrysler dealerships, and maybe it was just a more convenient method for replugging the hole, since the flutter valves would not need to be backordered, but why would a leaky plug be selected over a far more common ordinary oil plug that actually stopped the oil flow? A third possibility is that a misunderstanding existed between engineering and the catalog writers, and the writers stuck the wrong info into the Master Parts Catalog, reference:
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278824&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278823&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278828&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278829&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278830&original=1
http://www.supermotors.org/vehicles/registry/showmedia.php?id=278845&original=1
For more information on "flutter valves", just do a forum search (use the quote marks), but be sure you click on search only from the main forum page, since the search button fails on any other forum pages. An example is this post:
http://www.network54.com/Forum/74182/message/1057201748/W
If you can find more info on oiling restrictors, such as with the CJ block, please post specifics. I'm thinking there are no factory restrictors of any kind in that block, only restrictors installed by a prior owner.
If posting assistance is needed, instructions for signing up to post at this forum can be found at this link:
http://www.network54.com/Forum/74182/message/1134456134/R
Lastly, I've pretty much made this whole story about the plugs up, so it's best that you just look at the pictures and ignore any of the text I've written. My story makes some sense, but there are holes in it that I've not yet fully figured out.
JMO,
Shoe.
