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Tom-----
You are faced with a daunting problem here. In fact, I've given a great deal of thought to this type of situation for quite awhile now, even though it's not one that I, personally, have encountered or expect to encounter.
First of all, I presume that you don't want to add grommets to the early style valve covers. That's just as well, too. Although you could, theoretically, add the grommets, you couldn't add the oil seperator baffles which all 68+ small block valve covers used inside the valve covers, under the grommet hole. These baffles are critically important to oil control.
Basically, what you need is a "suction" point for the PCV system; you already have the intake point which is the tube which runs between your air cleaner and oil fill tube side fitting. There are two approaches that I could suggest as POSSIBLE ways to go.
First, you could check to see if your block has an unmachined boss on the rear which is the 'vestige' of the crankcase vent tube fitting. I don't know what era your block is from, but some of the "older" modern engines still had the block casting boss. If it is of very recent vintage, though, it will not have any boss at all. If there is a boss, you could drill and tap it for a 1/2" NPT nipple and use this as your "suction" point. If there is not a boss, you could drill and tap your intake manifold in an area that goes directly through to the lifter valley. The area between the coil mount and the rear intake passage might be a convenient point. The main problem with either of these "suction" points is that you will need some sort of an oil baffle/oil sperator on the underside to prevent excessive atomized oil from being drawn into the PCV system. I just can't figure out a way to do this, so I offer my second alternative.
In the second alternative you could install a fitting in either of the two places described above, but use it for the ventilation INTAKE point a la 1964-67 configuration. Then, use a the PCV valve in the line which runs to the oil filler tube, also like the 64-67 configuration. That would put the PCV system "suction" end at a point that wouldn't require an oil baffle/seperator. You still wouldn't have one at the the frsh air inlet end, but, perhaps, it would be less critical there.
The real "sticking point" in this whole conversion has to do with the installation of some sort of oil baffles/seperators, which are a critical element of the system. I have to admit that these are "far out" and untested schemes to deal with this installation, but they are all that I can think of.
By the way, another problem that you may face if you have an 1987+ model engine is that you may have cylinder heads which use centerbolt style valve covers. The original Corvette aluminum valve covers were perimeter bolt style. For this problem, if you face it, there is an easy solution. GM offers conversion plates to adapt center bolt style heads to perimeter bolt style valve covers. These machined billet aluminum plates are sold in a kit under GM #24502540 which includes 2 plates and fastners. It currently GM lists for $159.00.
You are faced with a daunting problem here. In fact, I've given a great deal of thought to this type of situation for quite awhile now, even though it's not one that I, personally, have encountered or expect to encounter.
First of all, I presume that you don't want to add grommets to the early style valve covers. That's just as well, too. Although you could, theoretically, add the grommets, you couldn't add the oil seperator baffles which all 68+ small block valve covers used inside the valve covers, under the grommet hole. These baffles are critically important to oil control.
Basically, what you need is a "suction" point for the PCV system; you already have the intake point which is the tube which runs between your air cleaner and oil fill tube side fitting. There are two approaches that I could suggest as POSSIBLE ways to go.
First, you could check to see if your block has an unmachined boss on the rear which is the 'vestige' of the crankcase vent tube fitting. I don't know what era your block is from, but some of the "older" modern engines still had the block casting boss. If it is of very recent vintage, though, it will not have any boss at all. If there is a boss, you could drill and tap it for a 1/2" NPT nipple and use this as your "suction" point. If there is not a boss, you could drill and tap your intake manifold in an area that goes directly through to the lifter valley. The area between the coil mount and the rear intake passage might be a convenient point. The main problem with either of these "suction" points is that you will need some sort of an oil baffle/oil sperator on the underside to prevent excessive atomized oil from being drawn into the PCV system. I just can't figure out a way to do this, so I offer my second alternative.
In the second alternative you could install a fitting in either of the two places described above, but use it for the ventilation INTAKE point a la 1964-67 configuration. Then, use a the PCV valve in the line which runs to the oil filler tube, also like the 64-67 configuration. That would put the PCV system "suction" end at a point that wouldn't require an oil baffle/seperator. You still wouldn't have one at the the frsh air inlet end, but, perhaps, it would be less critical there.
The real "sticking point" in this whole conversion has to do with the installation of some sort of oil baffles/seperators, which are a critical element of the system. I have to admit that these are "far out" and untested schemes to deal with this installation, but they are all that I can think of.
By the way, another problem that you may face if you have an 1987+ model engine is that you may have cylinder heads which use centerbolt style valve covers. The original Corvette aluminum valve covers were perimeter bolt style. For this problem, if you face it, there is an easy solution. GM offers conversion plates to adapt center bolt style heads to perimeter bolt style valve covers. These machined billet aluminum plates are sold in a kit under GM #24502540 which includes 2 plates and fastners. It currently GM lists for $159.00.