Hi, Using a diagram from a place like Ricambi (or a photo) would anyone be kind enough to show me where the idle adjust (valve?) is? My car is '76 308 carb. Does it ever get "sticky"? Thank you very much in advance, Mike
No such (singular) thing on a carbed 308. The airflow entering the engine at idle is controlled by the physical adjustments of the throttle linkages (which controls the positions of the throttle plates). There is a fast idle cam that should only be holding (all) the throttle plates more open when at cold start-up (but often this system is adjusted to be disabled). What is the symptom that you are experiencing -- too high warm idle sometimes? If so, the three most likely suspects are 1) carpet in the footwell , 2) a binding throttle linkage system, or 3) a sticky distributor advance mechanism.
Hi Steve, Thank you. The symptom that I am experiencing is that after I start the car (I'm not using the choke) the car idles around 1500. However, if I leave it alone longer most often (and, I would say always) the idle wants to creep up to 2000 and higher and higher. By pumping the gas pedal a few good times I eventually get the needle to rest at 1000. This is when I start driving. When I drive, the car performs fine and I have no high idle issues when at a light, etc. Thank you very much again.
That sounds more like your fast idle system is adjusted as intended (although your carbs must be set a little rich if it runs well at a higher idle RPM cold without the choke). Item 40 here: THROTTLE CONTROL - Ricambi America, Inc. is the thermo-mechanical eccentric cam that rotates as the engine temperature increases. When cold, it holds the throttle linkage more open via screw 45. As things heat up, it rotates and no longer contacts screw 45. If you'd like to disable, just back off screw 45 so that it doesn't contact the cam 40 when cold.
Thank you, Steve. Is this possible to do without having to remove the air box, etc., that sits on top of the carbs? Mike
Not sure (as it's been quite a while since I had a carbed 308) - "maybe" would be my guess, but perhaps a 308 carb Owner can comment more direclty.
Thanks, Steve. Hopefully someone will chime in here. Guys, my car is 76, very early steel carbed 308.
My car is an early 308 GTB S/N 20589. Attached are two pictures that show the cold idle mechanism. The first picture is a plan view of the device's location (it is the round shiny thing in the middle). There is an arm contacting it with a pivot point (under the bolt for the carburetor banjo fitting). Between the carburetor fuel line and the carburetor linkage is an sideways "L" shaped member. The cold idle device arm contacts this "L" piece to open the carburetor linkage. If you look closely at the contact area you can just see a nut. This is (on my car) the jam nut to keep the adjustment nut from moving. The second picture is a view showing the adjustment nut (it is the black button head for an Allen tool. I hope the orientation of pieces is understandable. I'm sorry that I do not know how to annotate the pictures themselves with arrows and the like. It might be possible to reach the device without removal of the airbox, but I don't think you'll be able to reach the jam nut. You might consider removing the screw altogether - it will not harm anything. Image Unavailable, Please Login Image Unavailable, Please Login
Using a jam nut isn't a bad idea, but the stock system uses a coil spring (item 46) to try to prevent the adjustment screw from turning.
Hi Hank and Steve, Thank you very much. Both replies are very helpful to me. And, appreciated. Would you know "why" the higher idle issue seems to "clear" eventually for me after a few good gas pedal pumps?
The spring inside the cold idle device is really rather weak and is insufficient to overcome the friction when the car is at temperature. I think when you depress the gas pedal it releases the friction and the cold idle device is no longer in action. Hope this is makes sense.
For what it's worth I can't seem to do *anything* worthwhile in that area without removing the bonnet and the airbox. Certainly makes things easier.
Steve and Hank, Thank you guys for the replies. I found them super helpful. The screw is visible under the airbox and I did not have remove anything. I was able to back it off (8mm) and now my car idles around 1000 like it used to - which is the way I like. I keep my foot to warm it up a bit around 1500 and this was the way I usually did it. I think the cars idling super high on cold is a lot to take on the engines. Thank you, again.
