roadblock69

I just picked up a '74 with an L82 and AC. It does not have a 6,000 rpm red line tach. I looked at an interchange manual and it does indicate that a car with AC uses a different tach than the a car without AC. The manual does not indicate the red line on either. I would like to know what the red line should show in my car. Thanks in advance.

jb78L-82

My 78 L-82 4 speed with AC redlines with the L-82 tach at 5,600 and my friends 78 L-82 without AC, redlines at 6,000. GM didn't want the R4 compressor spinning that high with AC. There is no difference in the motors. I don't have the compressor in mine installed and have not for years-rev it to 6,000. Hope that helps!

roadblock69

Thank you! I was surprised to see the tach red line at 5600 rpm. I knew the reason but failed to understand why GM would do that. If I remember the LT-1s with AC had a 6,000 rpm redline as opposed to 6500 red line on the cars without AC. I was surprised, and concerned that someone had messed with it. Thanks again!

calif phil

My '73 L82 A/C is also 5600