Gipper

While looking through the Tune up procedures in the factory service manual I see 2 different fast idle specs are given. (330 HC V8 - 4bbl carb with A/C)

In the text and tuneup chart it says to set idle to 850rpm with distributor vacuum plugged, but in the on car adjustment page it says to set the idle to 1100 rpm and that this is a new spec for 4 bbl carbs. 1100 rpm seems a bit high to me so my question is what do you guys set your fast idle speed at?

Brian

joe_padavano

1100 RPM fast idle speed with the car warmed up and the choke open (but with the fast idle screw on the fast idle cam) will NOT be that high when the engine is still cold and the choke is closed. Keep in mind that it is extremely difficult to exactly meet the cold conditions while setting this idle speed, as the engine is constantly warming up when it is running. The factory simply selected an equivalent fast idle speed to be set with the engine warm that will give you the correct speed when the engine is cold.

oldcutlass

Brian your idle speed should be 500 in drive, I've found sometimes 550 if it's equipped with air conditioning. The 2 rpm speeds your referring to is the rpm for setting your timing.

joe_padavano

Just so we're all clear, is the O.P. asking about the FAST idle speed, set with the fast idle screw on the fast idle cam, or the CURB idle speed set with the regular idle screw? These are two completely different idle settings for different conditions.

oldcutlass

I was also looking at this statement Joe, where he stated the vacuum advance needed to be plugged. I'm assuming the notes he is looking at are for setting the timing.

Gipper

THis is what I am talking about......
http://wildaboutcarsonline.com/membe..._Section_5.pdf

Look at page 5-6 step 3. Near as I can tell it is OFF the fast idle cam so it is curb idle. Am I missing something? I also am pretty sure if I set to 1100rpm curb idle 500-550 rpm in drive is not going to be doable.

What do ya think?

Brian

oldcutlass

Those are 2 separate adjustments with 2 separate adjustment screws. Step 3, the fast idle overrides the curb idle screw and is operational only when the choke is engaged. Step 2 is curb idle, normal operating temp and the choke is not engaged.

MDchanic

To be clear, here is the illustration you are talking about:



It says clearly: "Fast idle screw on low step of fast idle cam, and against shoulder of next stop."

I'm not sure what you're confused about.

- Eric

Gipper

I think what had me confused is that the car is fully warmed up. Isnt the fast idle cam used to bump the idle on a Cold engine?

Thanks for the clarification.....you guys are great!!


Brian

oldcutlass

Yes, when the engine is cold, and you pump the gas pedal to set the choke, the arm swings over and the fast idle screw will sit on the step once the pedal is released. After the engine warms you bump the gas pedal the choke releases and the arm swings back out of the way and the other adjustment takes over for curb idle.

Gipper

I knew thats what is supposed to happen so it seemed odd to me that you would set the idle with the engine hot....Thanks again for the clarification.


Brian

joe_padavano

Yes, and as I noted above, by the time you finish setting the fast idle, the engine won't be cold anymore, so it really isn't possible to set it correctly under those conditions. This adjustment is much more repeatable if the engine is at normal operating temperature and you set the fast idle speed under those conditions. When the engine is warm, you have to manually place the fast idle screw on the appropriate step of the cam. The factory determined that if the fast idle is 1100 RPM when warm, it will be appropriately lower when cold.

MDchanic

When the engine is operating properly, it gets to operating temperature and stays there indefinitely.
Therefore, operating temperature is an ideal temperature to specify for making adjustments of the type that would vary with temperature (such as idle and valve lash).

If not operating temperature, what temperature would be good? The temperature you would encounter on a winter day? Do you put it in the freezer if you are tuning it up in the summertime? "Room temperature"? But the car is outside. 70°? But what if it's 60° today?

Get the picture?

- Eric

joe_padavano

Gipper

Thank you all for the clarification. You guys rock.


Brian