quote Originally posted by dcarrd: I looked at some of the writeups in the forum and Im still a bit confused about this topic. What I gathered is that the Fiero compressor wont run at full capacity? Better off with the 3800 compressor but will have to get modified lines? To start: Its an 85 GT converted to a 5 speed 3800 sc Series 2 conversion(unknown donor, no AC compressor (blank pulley installed) PO removed the following for his other Fiero: Condenser Evaporator Collector I have: 84 Fiero with condenser, Evaporator and ac lines(no compressor) New collector My questions: 1. Can I use the 84 parts on the 85? 2. What setup works best, FIero compressor or 3800 compressor? 3. If a Fiero compressor is used, which one, 84 or 85+?(I think they are different)? 4. If a 3800 compressor is used, what part or donor info can I use at the parts store? 5. Is anything additional needed to be done to the 3800 or Fiero setup as far as hi/low pressure switches, lines, electric, relays, etc? 6. Which setup works best for this engine conversion? Thanks in advance...

1) 84 lines are completely different from 85-up lines since they were run differently in the 84 Fieros than later ones.

2) The stock Fiero A/C compressor has the wrong pulley on it for a 3800's serpentine belt. Also the spacing of the mounting lugs on the Fiero compressor may be incompatible with the 3800 A/C compressor mounting bracket.

3) If you can't use the Fiero compressor due to what I mentioned in #2, then this is a moot point. But if you can get the pulley changed and find a bracket to make the Fiero compressor work, then all you need is whatever set of Fiero A/C lines are required to mate up with the compressor you are using.

4) 96-03 used two different A/C compressors on the FWD 3800s (SC and N/A didn't matter). The compressor from a W-body (Grand Prix, Regal, Monte Carlo, Impala, etc) had both the discharge and suction ports the same size. The compressor from a C/H/G body (Bonneville, Park Ave, etc) had the discharge and suction ports different sizes which means the A/C lines that fit this compressor won't hook up to the W-body compressors. ~04-up 3800 A/C compressors were generally of the new Scroll type which use different A/C lines yet. These compressors are considered to be more efficient than earlier designs and directly mount to the 3800 block without needing additional brackets.

5) If you wish to place the A/C clutch control under 3800 PCM control, you will need to install a 3-wire A/C pressure sensor from a 96-up GM car on the high side line (requires welding on a fitting somewhere between the compressor and Fiero body A/C lines on the smaller of the two lines). This sensor will need to be wired up to the PCM. The PCM will need to be wired up to the A/C compressor clutch relay and the A/C request wire coming from the Fiero HVAC control panel. I have wiring instructions on my website describing how to do all of this. Once all this is wired up, there will be NO NEED for any additional pressure switches in the system so they can all be bypassed.

6) If you are doing an engine conversion and are going to be making A/C lines and don't yet have the compressor you want to use, I would get the ~04-newer scroll type compressor. If you order one for a 2005 Grand Prix with the 3800 Series 3 engine, it should be the scroll type. The scroll type directly mounts to the block without the need for any extra mounting brackets.

-ryan

------------------
OVERKILL IS UNDERRATED

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

[This message has been edited by Darth Fiero (edited 09-04-2014).]