67Rocket

Does any one know what the factory setting is for the idle mixture screws is for a 69 442 (325 horse power)? I backed the screws out 3 turns from closed position (per chevy tune up guide) but seems to run a little rich. Thanks.

rad

get it running and up to temperature, slowly turn the idle screw in until the engine stumbles then back out a half a turn, thats usually a good starting point for setting it

oldcutlass

Those recommendations are a starting point so the engine will start and run. You need a vacuum gauge or tach hooked up and adjust for highest vacuum or rpm while keeping both air/fuel mixture screws the same amount of turns out.

joe_padavano

^^^THIS!

The three turns out is only a starting point. You need to adjust them with the engine running. Use a vacuum gauge and adjust for the highest vacuum reading. This is an iterative process, as adjusting the mixture screws will change the idle speed. Reset the idle speed to spec then recheck the mixture screws and readjust as needed.

Lather, rinse, repeat.

MDchanic

The above are the correct answers, but let me add the specific answer to your question:

The '69 CSM gives no recommended number or turns to start with EXCEPT for all manual transmission 400s and all W-30s, which it recommends starting 6 turns out (figure 6M-102, panel #11, on page 6M-43).

- Eric

joe_padavano

The 1968 CSM (which is the one closest to me at the moment) says this on page 6M-35:

67Rocket

Thanks