Choke Pull-off

[rcmaniac791]

So whenever it is really cold, I have noticed that the 318 runs really rough until it's warm, then it runs fine. I also never have any problems starting the car. Anyway, I went under the hood while it was warming up and manually pulled on the choke linkage, and the idle smoothed out. It seems like the vacuum canister pull-off is pulling harder than the spring, and the choke is turning off too fast. Is there any way to adjust the rate of the choke pull-off? I did just replace the choke thermostat.

 

[AJ/FormS]

Many things are going on during the first three or so minutes after the car is started.Three things that are walking a tight rope, are the vacuum break(choke pull off), the choke spring preload, and the fast idle rpm. These all have to be synchronized. And as the engine gets older, the factory sync may no longer be perfect.
Without a service manual, the syncing of these is a trial and error procedure.
I'm guessing if this condition was pre-existing to the thermostat replacement, then the vacuum break needs to be increased. If this is a new thing, then I would back off the spring preload.
And don't forget the electric assist. If this is not functioning, then the choke spring will not come off fast enough, and the engine will run rougher as it warms up faster than the choke backs off.
The initial settings of these items sets the stage for a nice,quick, warm-up and a no-issue drive-away.
I would Check out the electric choke assist, and increase the vacuum-break a hair.

 

[shadango]

Timely post for us! We were tinkering today on the Volare and testing stuff, observing stuff etc.

Noticed that when vacuum is applied to the vacuum choke pulloff assist, it does work...however, it deosnt seem to "do" anything.....the linkage is attached to a slot in the choke linkage, where the electric choke thermostat gizmo is attached....the electric part does move the choke open....but the vac assist just moves in the slot.....effectively doing nothing....uploaded a video of what I am talking about. You can see the choke slowly open , its all the electric assist doing that.....

 

[AJ/FormS]

That is working perfectly.

1) The choke pull-off is inactive with the engine off.
2) When the engine is cold you pump a shot or two of gas into the carb
3) This action allows the choke spring to push the choke blade closed.
4) The closing choke drags the fast idle cam with it.
5) The choke blade should now be fully closed, and the fast idle screw should be on the second highest step of the cam. Now the engine is ready to spring to life.
6) So, you turn the key and it cranks, and starts to run.
7) Immediately the choke pull off receives it's vacuum, and cracks the choke blade open, about 1/8" to 3/16", to prevent flooding and/or rough running.
8) This action readies the fast idle cam to drop down to the next step.
9) You, the operator then tap on the gas pedal, releasing the cam, which reduces the racing engine to some more reasonable fast idle speed.
10) Over the next three minutes or so the choke blade will crank back to vertical as the Bi-metal spring unwinds due to the heat it is receiving.This step is where the video comes in.
11) At the end of this period you can tap-down the fast idle to the curb idle and if everything else is working right,motor away.
This is how it is supposed to work

I suspect your engine is running rough because at #7 the vacuum break is too much or too little. This is easy to prove. The next time the engine is cold, remove the air filter house but leave all systems attached to it, working. Then start it up as usual.
A) When the engine begins to run rough,open that choke blade just a wee bit. If it runs better; stop the engine.Turn the key all the way to off, to disable the electric choke assist. Find the loop in the connecting link, and close it up just a smidge. Reset the fast-idle cam by lightly closing the choke blade, while simultaneously opening the throttle. Close the throttle and then release the choke blade, which may or may not stay closed, depending on how long the engine was previously run.
Ok now start it up again, and notice the improvement.
This adjustment is a one time per cold start trial. If it doesn't seem to work you will have to try it again tomorrow, or at least 4 to 6 hours later.

B) But if opening the choke blade made it run worse, then stop the engine, and open that little loop a smidge. Reset the fast idle and restart the car. And note the improvement.
C) repeat as often as necessary
D) And that brings us to the timing of the choke element. If at the time of the full choke opening, the engine is not yet willing to be driven, Then it will want the choke to stay on a little longer. We make this happen in various ways with various carbs. I think your choke is stuck down in the cast iron manifold with a long link going up to the choke blade . This link usually has a loop in it for adjusting the decay rate.Make the link longer from end to end,by opening the loop,to make it stay on longer.
E) But before you do that, make certain that the engine is mechanically in good shape. That the valves are properly set and that all the timing systems are working and correctly set.And that the hot air system to the carb is also working properly. Any one of these systems,if not working right, will negatively affect the drive away of a cold engine.
F) The cold engine wants lots of timing, and a good amount of gas, and as little resistance to moving as possible. That means the brakes need to be releasing, the tranny is free,the A/C is off, the valves are not too tight, that neither the diff oil nor the engine oil is like tar, that the crankcase is not overfilled,and that the vacuum advance is working. From idle to 2000rpm or so the vacuum advance will be your primary source of timing at part throttle. If it ain't working, it's gonna be a sad day for you.
G)Remember, getting the choke system working on a 30,or 40 year old car is one of the most difficult things to do. Take your time. One change atta time, one cold-start atta time....Ok I think I about covered things, good luck

 

[Justwondering]

I have so much to learn.

 

[rcmaniac791]

Great info! the video is good to see as well.

I did the test yesterday where I opened the choke manually, and the engine smoothed out a lot. I also could tell that it was running extra-rich because the exhaust was extremely gassy during the warm-up period. I closed the loop in the linkage a bit, and this morning's cold start went a lot smoother. It didn't run nearly as rough, and warmed up faster. However, I think I closed the loop a bit too much because it took me 3 cranks to finally keep it running. I'm going to open the loop up just a hair and I think it'll be dialed.

It seems crazy to me that the adjustment is to physically BEND the rod.


As always, I really appreciate the help.

 

[volareandgtcat]

With all the help from this forum I got my choke working properly (last month) .. take your time and If I can do it most anybody can.

 

[AJ/FormS]

Great info! the video is good to see as well.

I did the test yesterday where I opened the choke manually, and the engine smoothed out a lot. I also could tell that it was running extra-rich because the exhaust was extremely gassy during the warm-up period. I closed the loop in the linkage a bit, and this morning's cold start went a lot smoother. It didn't run nearly as rough, and warmed up faster. However, I think I closed the loop a bit too much because it took me 3 cranks to finally keep it running. I'm going to open the loop up just a hair and I think it'll be dialed.
It seems crazy to me that the adjustment is to physically BEND the rod.
As always, I really appreciate the help.

Don't do it!
That is the wrong solution!

The correct solution is either
1)to increase the choke spring tension by lengthening the rod, or
2)More initial pump-shot.
But which one?
Well, the next time it is cold, and as soon as the choke is all the way open, tap it down, put it in gear, and attempt to drive away.
A) if it takes off without hiccups of any kind, then go to #2
b) if it sputters or stalls,the choke will need to stay on a little longer; go to #1.

But before you do anything; check that the accelerator pump is correctly adjusted, that it is correctly working, and that you are working it correctly with your foot!
Make sure that on a warmed up engine(key-off,lol) the butterflies open all the way when the gas pedal is floored.
When you first go to start the cold engine, You must pump the gas pedal all the way to the floor! Depending on the outdoor temperature, probably more than once.
If the engine starts revs up and then quits; then it needed more pumps. Add one pump and repeat.
On the next attempt when the engine is again cold you must remember how many pumps it took last time and repeat that.
When the overnight temp was close to freezing, it might only take 1 pump in the morning. If the temp dropped to -10*C overnight,(+14*F if my math is right) then it might take 1.5 or 2 pumps. If it dropped to -20*C(-4*F,I think) it might take 2 or 3 pumps. And so on. Every engine is different. You will have to get to know yours.
It is very difficult to flood most slantys.
Sometimes I have splashed about an ounce or more straight down the carb,got in, cranked it with the pedal down about half-way, and just held it there while it sputtered to life, then backed off as the revs began to climb.In summer even,lol.
OK, let me rephrase that; all the slantys I have ever had the chance to test, were hard to flood, by excessively pumping the pedal. I think you will nearly pump the bowl dry before you flood it,lol. So....point is ; don't be afraid to pump that pedal. And when you do, it's all the way to the floor!
But DON'T MESS WITH THAT ROD! if it runs good on the choke.
OK so good luck

 

[rcmaniac791]

DON'T MESS WITH THAT ROD!

I think that there is the possibility that you and I are talking about different rods.....I'll put a picture of the choke spring rod below. As you can see, mine is straight. The rod that I was messing with was the vacuum choke pull-off linkage.

I probably should also mention that this is a 318 and not a /6.

Typical start-up procedure that I do:
1. pump gas petal 2-3 times (I'm not afraid of wide-open, running or not!)
2. turn key, always fires right up
3. run at fast idle until I see some temperature in the gauge
4. tap throttle to lower RPM
5. let engine settle for a second
6. drive off.

It is also worth mentioning that I installed a reman. Carter BBD a little less than a year ago, and never did any adjustments to it.

 

[BudW]

Carburetor linkage is normally adjusted by bending the rods at pre-determined bends.

The rod coming from choke thermostat is different and that rod stays straight (ie: not bent).

IF there is ever a need to adjust that rod (thicker than normal carburetor gasket, is one example), then there is another method of adjustment – which (again) is trial and error.

Take the picture above, and flip the choke thermostat over (wire side down). There will be a nut, some lines with a “+” and “-“.

Now with that said – I have made thousands of carburetor adjustments over the years – and have yet to make a choke thermostat adjustment.

Generally, the problem I find with it, is the bi-metallic spring in the thermostat has rusted or basically wore out and won’t move to specs anymore (which requires a replacement).


AJ/FormS did a very good write up on what takes place on startup. I have a few very minor differences – but for the most part not enough to alter what he said.

It helps to know what happens - then watch it happen.
BudW

 

[rcmaniac791]

I know that Chokes are never really easy to adjust, I'm just being patient with it and doing a little here and there.

that being said, It warmed up good this morning. Fired right up and didn't run rough during warm-up. I looked at it more and determined that the choke was not being pulled off enough during the initial start by the vacuum canister on the carb, causing it to run extremely rich and run rough.

If it keeps running like it did this morning, I should be good. Now that I said that, I'm sure it will need more fiddling haha.

 

[AJ/FormS]

Hyup, I blew it. So sorry. But I see Bud got you fixed up, in post #10.
I guess I ran off the rails at #3 already . My apologies

 

[kkritsilas]

I think that there is the possibility that you and I are talking about different rods.....I'll put a picture of the choke spring rod below. As you can see, mine is straight. The rod that I was messing with was the vacuum choke pull-off linkage.

I probably should also mention that this is a 318 and not a /6.

Typical start-up procedure that I do:
1. pump gas petal 2-3 times (I'm not afraid of wide-open, running or not!)
2. turn key, always fires right up
3. run at fast idle until I see some temperature in the gauge
4. tap throttle to lower RPM
5. let engine settle for a second
6. drive off.

It is also worth mentioning that I installed a reman. Carter BBD a little less than a year ago, and never did any adjustments to it.

View attachment 19369

Is there a name for the little fasteners that keep the choke spring rod on the carb choke lever? They look like aluminum push washers, but I don't know the correct name for them. I need to find one for the 1981Mirada CMX, as the P.O. lost the rod, and the fastener with it. I have a replacement choke unit and rod, but would like the fastener as well.

 

[BudW]

I’m not sure which part you are referring too.

Can you “copy” the picture below?
Open the picture in Paint (or whatever photo editing program you have) and draw an arrow or circle on where you are referring to, exactly.
Then repost the picture here?

With that information, I can get you an answer.

Note: the picture is from my ’86 5th Ave 318, which has a Chinese repop non-Lean Burn ’77 Carter BBD on it.
Holley 2280/6280 will look close, but not quite the same.
BudW

 

[rcmaniac791]

AJ, It's all good! That's the beauty of this site is that we are all here to learn from each other.

a Chinese repop non-Lean Burn ’77 Carter BBD

I didn't know china was producing those. How's the build quality/price compared to an original or reman Carter?

 

[BudW]

My ’86 5th Ave still has the Lean Burn (ESC) computer onboard and is controlling the ignition timing and is thinking it is still controlling the carburetor (but this carburetor has no mechanisms for electronic fuel control).

I have the parts needed what I needed to get rid of the computer – but is on a long list of things to do. It might get done before the big block gets installed, maybe . . .

I bought that carb on eBay about 5 years ago. It was advertised as a “new” ’77 318 BBD. No mention of Carter or China in the listing.

The carburetor has been working fine for me. My Holley 6280 is in my garage (hiding from me) somewhere – which I could bolt back onto car if I wanted to.
FYI – I am not a Holley person and will remove one/get rid of one ASAP.
Carter carburetors has always been kind to me – and I have rebuilt hundreds of them (not quite thousands – but close)

This arrived in mail in a plain cardboard box and was packed so-so (had better and seen a lot worse).

It came from California, I believe. There is NO Carter markings anywhere on it. It also did not have any carburetor stampings on it (like 8145s which is the number on my Wagon, or any date codes) – which is why I call it a Chinese repop.
There are casting numbers on the different parts.

Looks and how it functions, I don’t see any differences (other than what was mentioned above) and it performs like it should, out of the box.

- - - - -
I DO NOT recommend anyone purchasing a “rebuilt” carburetor. If you do, at least keep your old one until the replacement works ok.

Carburetor rebuilders keep carburetors in groupings like ALL BBD’s are in one group. They will build a group of say 30 or 40 BBD’s, then 30-40 of Quadajets, then 30-40 of (pick a name). So during the build session, they will dissemble all 30 (or 40) of that carburetor iype and toss all of the parts in one pile for cleaning. They then wash all of parts, picking out the good from bad. Replating what needs refinished, and so forth.

Then they stack all of the parts in different piles (all jets in one pile, all tops in another, etc.).

Then reassemble the group of 30 (or 40). Jets get mixed up, well – everything gets mixed up. It is a wonder that much of anything rebuilt in that fashion even works.

I don’t know all of the differences on BBD’s - but I do know them on TQ’s.
There are 5 basic different groups of TQ’s, that fit Mopars. All 5 are different and only a few items can successfully be swapped between the 5 different groups. Jets, floats and metering rods will interchange on the last 3 groups (the most popular ones). Jets for a 440 will be different then say a 318, and so forth.
Example jets on a ‘79 318 car has 0.089” primary and 0.110” secondary jet sizes.
’78 440 HP 49 state has 0.100” primary and 0.143” secondary jet sizes.

Can you imagine how well either engine will run, if you had one primary jet at 0.089” and other at 0.100” (or Secondary’s at 0.110” and 0.143”)?
One side will be way rich (or lean depending on engine).

Note: Carter jets come in 0.001” increments

I have seen main body’s, tops and bases miss-matched and so forth. I just have to shake my head on what they will let out the door.

Really, if you re rebuilding carburetors in mass as a business – I don’t know of a better way to do it – unless you could keep all of one carburetors parts together – but mass production just won’t allow it.

A local carburetor rebuilder (for those few left out there) do them one at a time (the right way and way I have always done it).

Getting your existing carburetor rebuilt or getting a new one – go for it.
Getting a box marked “rebuilt” – no way – not without going completely through it first (which defeats the purpose).

If you get a box marked “rebuilt” and it works fine for you – then you are one of the few.

If I talk to someone and they said, I just had a carburetor put on it and car is acting up, I can just about guess with a high percentage of accuracy, they had a ”box marked rebuilt” installed.
BudW

 

[rcmaniac791]

If you get a box marked “rebuilt” and it works fine for you – then you are one of the few.

I guess I am one of the few. I bought one of those "rebuilt" carbs from summit. Well, re-manufactured is what it said technically. No adjustments needed, just a quick bolt-up and turn the key. I did have to replace the bowl gasket, but only because I bought the carb in 2016 and it was rebuilt in 2010. 6 years of sitting on a shelf dried out the gasket I suppose.

 

[kkritsilas]

I’m not sure which part you are referring too.

Can you “copy” the picture below?
Open the picture in Paint (or whatever photo editing program you have) and draw an arrow or circle on where you are referring to, exactly.
Then repost the picture here?
View attachment 19404
With that information, I can get you an answer.

Note: the picture is from my ’86 5th Ave 318, which has a Chinese repop non-Lean Burn ’77 Carter BBD on it.
Holley 2280/6280 will look close, but not quite the same.
BudW

BudW:

I am looking for the round washer on the inside of the clip and washer your picture shows. It is for a TQ, if it makes a difference. The choke rod goes through the clip, washer, add plate, and comes out the other side ( between the inner surface of the carb plate and carb body). There is usually some sore of retainer/push washer (most are aluminum, I think) to keep the rod from pulling out. I need to know what that retainer/push washer is called.

 

[AJ/FormS]

I have not seen that many TQs but all the ones I have seen, used the same clip as shown.

But it sounds to me like you are after something called a Tinnerman nut: tinnerman nut - Google Search:

 

[BudW]

I have somewhere around 80 to 90 TQ’s in my garage (I’ve no idea why that many). I can look when I get home and provide some pictures and measurements

I provided a couple of pictures I swiped from eBay.
Could you point out which items you are looking for (picture number and area within that picture), please?

1.

2.

3.

4.

5.

6.

7.
BudW