Twan Sloot

Hi guys,

Today was the first day I had a long drive with the c2 and I noticed that when the fast idle cuts out the idle will go to 450 or so. When I am parkerd it will run 450 but of course that's t too low, and while driving it will die when you brake and the clutch is fully pressed. As soon as you give a little throttle it runs great and won't die.
The car also gives little humbs when you drive a constant rpm let's say 1800 rpm in first gear, if you try to keep it at that rpm constant it will humb a little.

Ps the first 10 minutes of driving when the choke is still engaged the car runs absolutely great without any mistake, and no humbs at all

I know the idle should be around 750 but I am not a carb guy so what's the best way to approach, I have a 1966 327 300 and the carb is a holley with electric choke.

Thanks!

Scott Marzahl

It sounds like your curb idle screw needs a slight adjustment. Just go to youtube search holley curb idle adjustment. You need about 1/2-3/4 turn on it to bring idle up to 750-800 rpms.

Twan Sloot

Great will try that tomorrow

Thanks

Nowhere Man

Make sure all your vacuum lines are good first

irwiny

Maybe also check your return spring. My car would idle inconsistent high and at times when coming to stop. Low(500~600) when the car was parked after driving -> restart. I reduced the length on mine to minimize any free play and it worked so far for the high idle and starts up fine after parking.

Twan Sloot

Okay I turnend the curb idle screw clockwise 3/4 of a turn, it didn't seem to do so much, it did idle a little higer I think. Didn't had the time to test with engine running and turning the screw at the same time, just turned the screw 3/4 and went for a drive, after 5 minutes idle dropped pretty low again did not die allthough.

Give it some more turns or start to look for other things?

Nowhere Man

Sounds like you got a vacuum leak or its running out of gas

Twan Sloot

I kind of get the idea it runs to lean because with the choke engaged it runs absolutely fine and drives fine, and when the choke cuts out after 5 minutes it only runs good when you have the throttle pressed (even a little is enough).

Nowhere man, you are talking about the vacuumadvance I suppose, how to check? the line from carb to distrubutor is fine.

phil2302

Twan dont be fearful of giving the idle screw some more turns. Do it after the engine is warm. Worst case is you wind up with an idle that is too high. If that happens you can lower the idle by turning the screw in the opposite direction.

Twan Sloot

Yeah that was my planned next step, but I ran out of time.
And it started raining

Nowhere Man

You have the vacuum Advance can that can leak or your intake gasket could have a leak or the carb gaskets. If you have power brakes that could be anther source. Plenty of problem areas but should take less then 10 mins to figure out

Frankie the Fink

Snug down the carb mounting bolts and any screws that hold the carb body together (WCFB or AFB). An unlit propane torch passed around likely leak points with the engine running will show up a leak if the idle increases at some area...

leif.anderson93

Key word here...maybe a quarter turn past finger tight. You can bend the carb ears very easily.

Twan Sloot

I will try to give the curb idle some more spins tomorrow and if that doesn't help, I will dive into the vacuum.

Will update tomorrow

Thanks!

Twan Sloot

That's a cool tip

Frankie the Fink

And it actually works...

Another key word: UNLIT

Twan Sloot

Yeah luckily I already took notice of that one
But pretty logical since you want the propane to be sucked in

tbarb

Is this a problem that just started and the carburetor and adjustments were fine before. How old is the fuel in the tank.

The proper method to set the A/F screws is the get the engine good and hot and set the idle speed at your 6-700RPM then adjust the A/F emulsion screws to get the highest vacuum or idle, keep the screws on both sides approx the same turns out.

Twan Sloot

Well I only have the car 7 months or so and because of our really wet winters this was my first longer drive than 10 minutes, and I first noticed the problem after leaving the highway the engine was nice and hot and it would idle real low it even idled for 350 for a second or 10 after that it died and would fire right up and as soon as throttle is applied it drives like you would expect it to do. The next day nothing wrong start up the car idles at 1500 until I drive it for 5 minutes (choke cuts out because engine is warm) and the car idles at 450 again and eventually it can't stay on with the extreme low idle and dies, again fires right up.

Edit: forgot to mention the fuel is 7 months old, filled it up when it arrived with 98.

tbarb

Get it good and warm and go through the idle adjustment mentioned above. It's a pretty standard procedure that is used when a engine is tuned up. Take a few minutes and make sure the dwell and timing is good, gotta start there.

FWIW, to set the idle speed on my 1967 300hp engine the idle speed screw is usually turned approx 3/4-1 turn after contact which yields approx 650rpm. If you are way off that it's possible there is a problem with the carburetor.