I installed a remanufactured carb on my 68 Camaro with the inline 6 250 with Powerglide trans. It has the 1 barrel Monojet Carb.

I solved the off idle hestitation problem, but now have another issue.:(

It does not run very well for the first minute or so after starting it. It surges and dies unless I give it throttle, or manually open the choke.
After it warms up and the choke is open it runs fine.

I know it is a choke/fast idle cam problem , but I am not sure what to look for or how to properly adjust it.
I am ready to throw in the towel and take to a shop to have it adjusted.

Anything I can check or adjust to fix this?

start it up cold and adjust the fast idle speed screw

Search online for the "rebuild directions" for that carb. Most carbs have some sort of "choke pulloff" to open the choke slightly, generally 1/8" of an inch, immediately after the car starts.

When you start the cold engione, you should jack the gas once to set the choke. At this point, the choke should be completely closed, and the throttle on the top step of the fast idle cam. Do this with the air cleaner off, from stone cold.

Then start the car without touching the throttle. She should start. Adjuct the fast idle screw to give a comfortable fast idle, and observe that the choke has opened slightly.

The whole thing is kinda tricky. Chokes just aren't a very good way to do this.

On the side of the carb, there is a fast idle cam with 3 steps on it. When the rod coming up from the choke stove is adjusted correctly, the flat part of the linkage should be resting on the step that is protruding the most. That will give you your fast idle. Make sure the eng. is cold, remove the air cleaner and pump the throttle by hand to set the choke. If the choke is not closed as it should be, bend the rod coming up from the choke stove to close the choke and see if the flat is on the highest step on the fast idle cam. I too put a new carb. on my 67' and had to tweak it a little to get it right

Tom

I took it back to the carb shop and they determined that the choke pull off was not working.
They repaired it and it starts and runs better now, but I am trying to get the idle mixture dialed in to get it to idle smoothly. It runs on/diesels when turned off at times. Is this too rich or too lean?

The timing is right at 4 degrees btdc. as per specs.

The run on could be from too high of idle or very rich leaving deposits that glow and keep ingnition going. You can set mixutre good at home with alot of fiddleing around with propane and other ways but best get it right at a shop with a co hc detector and be done worth the couple of bucks and time. you should see readings around 2. to 3. % co. try to obtain low hc as posible then lean it just a touch from there. Before you go run some carb cleaner though it and then change the oil. High speed should be leaner around 1 1/2 % co. May have to rejet to get that.

I would check the idle when warm as previously stated. That will cause a run-on condition. I have my timing set a 8btc and my eng runs very good there. I might bump it up to 10btc and see how it works out. I set my mixture by running the screw in until the rpm starts to drop off then back it out until it does the same and set it where i get the highest rpm and reset the idle.

Tom

67, Do you have the 250/Powerglide in yours?

The spec is 4 degrees btdc. Doesn't retarding the timing bring the idle down.

I just can't seem to find the right mixture.

It still runs way too rich when started cold, I am assuming the choke is not opening far enough. Is there an adjustment for that?

I am ready to take the carb back and demand another one, but I am worried that they could give me one that is worse....

I may just bite the bullet and take it to a shop and have them mess with it.
It runs fine going down the road(higher rpm), so It must be in the idle circuit or choke.

I checked for vacuum leaks and all the vacuum hoses are new.

One thing I noticed is that the Vacuum port at the base of the carb that goes to the trans modulator has little or no vacuum.
Is this normal?

When warm, after starting it the engine it kind of surges until you press on the throttle, and then evens out.

That could be a lean surge. That would also make it seem rich due to smell, High hc.
When cold try taking the air cleaner off then have someone start it by pumping the gas twice then cranking. Watch what the choke is doing. It should be all the way closed untill the engine vacume opens it up a crack. It may need to be a little more closed or open. Just something to try. You say it runs fine when warm right?

yes, it runs fine when warmed up.

How is the choke opening adjusted?

Well , I havent looked at that carb for 20 years so this is my best at memory. On that carb I think you could adjust the high Idle with a cam screw, and to adjust the choke time it stays active was just a coil spring that would loose its umpf, to adjust the position of the blade in the carb after the pull off was active (engine running) was bending the rod. Before you do anything tho try moving that choke blade ( it has some play) when cold (engine running) to see what helps ( alil more open or closed) If the engine speed picks up when you close it some its too lean of a choke. I only check the site in the morning.

The engine speeds up and smoothes out when the choke is opened more.
There is no screw for fast idle.
It is adjusted by bending the tab that rests on the fast idle cam.
It looks like the choke needs to open more, but I am not sure how to adjust it open more.

OK its too rich, double check the choke pull off is really moving when you start the engine. ( Its a plasitic diaphram with linkage to the choke). If not replace it. ( you will need the carb # to get the right part) Does it get a faster idle when cold? I know it runs rough but does it seem a bit faster than when hot? You dont want to adjust anything untill all the parts work for sure.

I do have a 250 and (formerly PG) now 200-4r. When you set the timing at btc, you are actually advancing it. Atc is retarding it. Assuming the carb was rebuilt correctly by where ever you got it,try this. Remove the air cleaner and pump the throttle by hand to set the choke. The flat tab on the linkage should be on the highest step on the fast idle cam. Start the eng,the choke should open slightlyto let some air in. If it does not,and you have already said the carb people fixed the choke pull-off, it could be the rod coming up from the choke stove is adjusted wrong and is holding the choke closed too much.You can bend the rod a little at a time to correct this.Also, does the choke open completely when the eng is up to temp? If possible, have someone look at the tailpipe when it's running to see if there's a lot of black smoke. Hope this helps.

Tom

I dropped it of at a shop today. He mentioned that it may have the wrong base gasket which makes sense to me.
As I mentioned before,there is no vacuum to the port at the base of the carb that goes to the Auto trans modulator, and he is guessing that the same vacuum supplies the choke pull off.
Looking at the gasket, it is a solid gasket(no holes except for the mounting bolts), but I looked up the gasket online at Partsamerica and Autozone and they both show pictures of the gasket, but the gaskets they picture have holes or notches in them that mine do not. He is guessing that the holes need to be in the gasket to supply the vacuum to the choke pull off.
Does this sound like it makes sense? Here is a picture of the gasket that both Autozone and Kragen picture as the correct gasket for my car.
http://www.partsamerica.com/product_images/img/thumbs/fel/tn_60258.jpg (http://www.partsamerica.com/ProductDetail.aspx?MfrCode=FEL&MfrPartNumber=60258&PartType=520&PTSet=A)

Sure does todd. Its worth a try. If you dont have vacume to it thats just what will happen in the mornnin. Once that choke pull off works it will act very different when cold. probably all good different. Let us know how it turns out.

Thay was it.....I was using the generic gasket that the carb rebuilder gave me.
I went and picked up a new $2.00 base gasket at Carquest, and the Mechanic installed it for me and set the mixture.....problem is solved...

thanks for all of your help and tips..