The elevation of the radiator or any other part of the cooling system is totally irrelevant. The tubes are there because there is no other way to get air out of the heads without them. Yes, you could bleed the air out of the tubes and then cap them, but you would have to do this every time you filled the cooling system. The air can not flow down into the block to get out. The tubes are at the top of the heads because that is where the air accumulates, and if you do not bleed it out, it will make the head run hot where the air is. When there is a pocket of air in the top of the head, then no water is in that section of the water jacket, why is that so hard to figure out? The engineers made an air trap in the heads of LS engines, but they resolved it with the bleed tubes, I would leave them in service. They did not put them in just for grins, they are needed to get the air out. Other manufacturers have had similar problems in other engines, and they have put in manual bleed valves to remove the air. GM chose to make the air removal process automatic, so why not take advantage of it? GM will not remove the air bleed tubes because they are needed. The routing through the TB on Gen III engines was just convenient. once they found out that heating the TB was not necessary, they removed the tube from the TB. They did not remove the air bleed tubes because they are necessary.
Look at the first entry in the table. How do you know you are only drawing 15" of vacumm in the center of the pump impeller?
Measured it. Since you can measure the vacuum or pressure without actually contacting the chlorine solution in the pool water, I was trying to design an alarm system, to tell me my pump was cavitating without using a flow switch, since they got eaten up every year. So yes I know there was only 15" of vacuum there, actually, it was less then that most of the time. By the way most of the time when the pump cavitates, there is less vacuum present, then when it isn't. Using your 100K mile theory, since I only change my oil every 25K miles and have gotten over 250K miles on several of they doing that since new, it should be OK to do it an any vehicle, using any type of oil. I use Amsoil, but using your logic that should mater. In fact I've never had a motor fail, for an oil issue.
It seems like blocking the steam line/vents and "burping" the system through the block-offs would make sure there isn't any air trapped. GM, likely, wanted to foolproof this system and not rely on some mindless hack (there are quite a few) to vent the system properly...a job well done, by the way. This eliminates any warranty issues related to human error and not venting the system when opening the cooling system.
Why do we mod/tune our cars, at all, if GM has engineered everything so perfectly??
I plan on drilling and tapping mine and putting -3 lines to tie them into eachother and to the radiator.
Should be able to do it and make it very clean.
Tim
__________________ 86 Mustang
428ci w
tfs tw, FTI cam, pump gas, radials, 10.08 133.14 1.374 60' has been 1.3142 60'
418 ci L92, vic jr, 4 hole, c4 8" converter. 9's on pump gas is the plan
as i read this thread i laughed for about ten minutes. "pissing match." "i can out piss you." you guys got to be kidding. anyway my solution is simple, if you dont want to tap the waterpump, tap the radiator like i did. all the books i read have the steam line running to over flow, radiator, heater core, or water pump. my suggestion to you is to send somewhere rather than just capping it. good luck.
