'91 LS400 Air Cond. Pressure relief valve

[cutlass275]

I just replaced the entire AC system with new parts. Denso compressor, Denso core, etc. The new compressors do not come with the top plate where the lines attach and etc....one must swap over from the old compressor. No problem but....The pressure relief (or pop off) valve is defective we find. Lexus will only sell the entire top piece ($300) even though the relief valve simply screws right into the side very easily. There are multiple thread sizes we see though and rather not resort to a junk yard valve. SO, does anyone know where I can by the valve alone? OR...one that fits....OR what the actual pressure it pops off is, as I have a vendor that I can buy valves like this from (Not necessarily automotive).  Thanks

[Exhaustgases]

Wow a nice way to over charge for a cheap part. Even the whole base plate should not tip the scales more than $50. Please keep this updated if you find the part cheaper some place.

I have a question so if that relief valve pops off does it just release the refrigerant? I don't think the pressure should go higher than 150 psi

[cutlass275]

YES! I did find the proper valve sold separately! A nice service manger (old school) at the local Lexus dealership told me these were GM relief valves! (Yes, Lexus bought some American parts to use on some of their cars in manufacturing).... This relief valve is Four Seasons part #35745. $16.00 total!! This part number crosses over to many different aftermarket AC manufacturers and can be bought at any parts store in the country! The pop off would be in the 400-500 lbs range and yes only Freon would escape. Lexus did NOT want anyone to know that these were U.S. MADE relief valves they used on their 1st gen cars!  16$...it screwed right in and my air is working great!