How Much R134a Charge for My A/C System?

[DoctorMuffn]

I have a '73 240Z with a retrofitted (if that even qualifies as the 240s didn't come with A/C anyway) A/C system. I need to know how much of a R134a charge it will need.

I'm working on my system at school in automotive A/C class, but I've yet to find any hard facts on how much charge it takes. The most I know about it right now is that it has a massive York Compressor. Unfortunately the compressor's clutch is constantly engaged when I turn the A/C on which will be another problem I have to address.

Any help on how much charge I put in the system will be great. Thanks!

The Doctor

[Xargon321]

its like 85% percent of what it fills with r12

[DoctorMuffn]

How much charge of R12 would I need? I can do the math, but I need to start with a base figure of something.

Thanks