Quote:
Originally Posted by jnewt
I believe the automatic trucks had three lines. Supply, return and the EEC vent. The manual trucks had two lines. Supply and EEC vent. Ive read somewhere the return line was to help with vapor lock issues.
|
No
If we assume GM's parts book doesn't lie on the subject, and I don't believe it does in this case, return lines were installed beginning in 72, not to say late model 71 wouldn't have one. My 71 A/C 402/400TH didn't have a return line. The pick-up is one line and the pump the same. More confirmation is my retainers took no more than three lines (brakes, vapor, gas). Some of the retainers take four with a return.
But seems you're right about automatics, at least some. I know a 72 with a TH transmission calls for a return line. You may be right about vapor lock too, perhaps more prone with A/C on? My truck has never vapor locked, knock on wood.