start then stall...

[Bonnewagon]

Yes. You are closing in on it. Very good. Now you see how it works and can adjust it properly. Being colder weather,it is likely wanting to be closed a tad more. Don't forget to do as pontiacgp suggested. If there is a thermal vacuum valve in the ditributor vacuum line it should be closed (no vacuum) until the motor heats up. Two vacuum lines that meet into one? Sounds like ported (carb) and manifold (manifold) vacuum meeting at a vacuum regulator valve (VRV) that gives about 10 inches of manifold vacuum to the distributor, then as the carb opens ported vacuum takes over the advance function. This can be tested with a vacuum gauge.

 

[billyjack]

You got it. Start it up cold, and adjust the break until it's open about 1/4 inch, using a drill bit or bolt as a gage pin. See how it runs on the next cold start.

Bill

 

[Bonnewagon]

Is this a Canadian 231 V-6 with dualjet? Because I'm not getting anywhere finding specs for you. According to Alldata it should be a ccc motor with computer controlled advance or was it backfitted with non ccc parts? Anyway do as billyjack said and start with about 1/4 inch drill bit and see how close you are to that gap. You allready see how to adjust that. The 83' dualjet specs are listed in degrees of opening and unless you have the tool it is tough to get that measurement.I posted here rather than your PM since others may be reading this thread and might find the information usefull.

 

[83cutlasssedan]

The car is Canadian built. The dualjet is stamped made in USA. I'll try the drill bit and see how it goes. Thanks anyway.

 

[Bonnewagon]

That's what I thought. Pre ccc cars show vacuum break specs like this- front: .117 to .243 which is about 1/8th to 1/4 inch range. Rear-.090 to .220. Apply vacuum to the valve and measure your butterfly opening and proceed from there. I tend to like it a wee bit rich so I adjust it down until it starts and fast idles cleanly with just one pump of the gas pedal. As billyjack said, only way to be sure is a cold start in the morning.

 

[83cutlasssedan]

I would bet that the pre ccc specs would be the right specs for my car. Thanks for looking that up.

 

[pontiacgp]

You got it. Start it up cold, and adjust the break until it's open about 1/4 inch, using a drill bit or bolt as a gage pin. See how it runs on the next cold start.

Bill

make sure you have a magnet with you in case you drop the drill or bolt down the carb...

 

[83cutlasssedan]

I was just wondering about the front vacuum break. I can see the rear vacuum break working so I can understand how that one works, but I am not quite sure how the front break works in the system. Can anyone clarify?
thanks

 

[billyjack]

Every Rochester I've ever seen with 2 vacuum breaks has a bleed hole in the rear break to delay opening. If you check /adjust it with a hand held vacuum source, cover the bleed hole temporarily with a piece of tape. The principle behind two is for one to open the choke as soon as the engine fires, and the second to open it slightly more after a few seconds, allowing more air thru the carb as the rpm ramps up. Pre-emission carbs weren't so finicky about choke adjustment, since they fed so much more fuel at idle. When the mfrs. leaned the carbs way down to meet emissions specs in the 70's, choke adjustment became more of a science in order to maintain decent cold driveability. My advice is to get it in the ballpark, then adjust only one thing at a time until you get it dead-on.

Bill

 

[Bonnewagon]

As Bill said, the front opens the choke butterfly immediatly. Test by either applying vacuum with a MightyVac, or a length of clean vacuum line and just suck on it. It should apply and stay applied. Put your finger over the end of the vacuum hose and if it stays you are good. If it slowly retracts then the diaphram inside is leaking and time for a new one. Another way is to remove the rear one's vacuum hose and start the motor-if the front alone won't open the choke-you have a bad one. The screw on the plunger shaft with the green spring is how you adjust it. Older models, and maybe the rear one, you had to bend the rods to adjust so be glad you have the screw type.