68_Cutlass_S_Convertible

1968 Cutlass 350 original 2-barrel carb. Just had the carb rebuilt so am going through the various adjustments in the manual. I have the warm idle currently set to 600 in drive (manual calls for 575). In Park, the warm idle is about 670 with the idle comp disconnected and 700 with the comp connected. Fast idle cam is in clearance notch. I did have a vacuum gauge connected to the large port at the base of the carb during this test because I had been checking the two idle screw settings. Fast idle set to 900 on low cam position following the manual.

I'm a little confused about what the warm idle speed should be in park. In the tune-up section of the manual, it says to set the idle to 850 to check the timing so I took that to mean that warm idle in Park should be around 850. I'm obviously at 700 (comp connected) albeit with the air cleaner off and vacuum lines capped which I think is still right for checking timing. What's the right warm idle speed in park? It wouldn't really make sense to me to adjust idle to 850 just for a timing adjustment and then reduce it back down but is that the right procedure?

Dumb question time: What causes the Park idle vs in-gear idle to be different and is it possible to adjust the park idle separately? I feel like I followed the manual but my Park idle is definitely not 850.

Thanks in advance.

Fun71

That is exactly what you should do. The spec for my engine is 10* at 1100 RPM, but 1100 RPM is definitely not the idle setting.

Set the timing at 850 RPM, then set the idle speed to 575 RPM in drive like the manual says. The RPM in park will then be whatever it will be.

joe_padavano

Drag from the torque converter. In PARK the trans is in neutral and the converter spins freely with no drag. In gear the engine is loading the converter. The driven impeller in the converter is rigidly connected to the trans input shaft and won't be turning when the trans is in gear. As noted, set RPM in gear. PARK RPM will be what it will be.

68_Cutlass_S_Convertible

Thanks. I raised the RPM to 850 warm and adjusted the timing slightly for 5 deg. Timing adjustment was pretty sensitive so I went back and forth about 5 times trying to get it right. Then back down to 600 RPM in gear (a slight pad over the 575 in the manual).