Rough Idle and Occasional Stall on 68 200

[dudeigota66]

Ive got a 200 that takes quite a while to warm up and will not start without me having to press the gas pedal. Once it does start it idles for a few turns then shakes a little, then it idles fine and does everything again. It runs perfect! Absolutely great on the road its just at idle it lags. We recently changed it to electronic ignition and it has one of those Holley/Autolite replacement carbs for the 1100. It has the choke with the pipe that goes down to the exhaust.

This wouldn't be an issue because it runs absolutely smoothly, but after i start it and then drive without giving it at least five minutes to warm up it stalls. I don't like it when it stalls which is why im coming to you guys to see if anyone had an idea of what it could be. La ter on today I was gonna vacuum gauge the carb to make sure eveything's right. I might also do a timing check with a light or something. Or is this normal? It does however take a while to run up to eighty or ninety on the freeway, and it has trouble with uphills but I think that's my tranny it might need a rebuild because it takes quite a while to shift from first, i can tell it holds on to that gear for quite a while cause once it lets go the car gets a nice speed boost. Any help is great. Thanks guys.

 

[JackFish]

What is the timing set at?
Bumping it up a little bit can make a difference in throttle response, but you might have to adjust the carb idle to compensate for the increased rpm.

 

[dudeigota66]

I think the timing is around ten or twelve. I havent messed with the carb much because at one point i had it as low as i could without it stalling and it would take ages for it to warm up. I finally got tired of it stalling when i shifted that i decided i would run it a little higher.

Could it be a timing issue though? Would that affect the way it idles?

 

[chad]

Ive got a 200 that takes quite a while to warm up and will not start without me having to press the gas pedal. Once it does start it idles for a few turns then shakes a little, then it idles fine and does everything again. It runs perfect! Absolutely great on the road its just at idle it lags. We recently changed it to electronic ignition and it has one of those Holley/Autolite replacement carbs for the 1100. It has the choke with the pipe that goes down to the exhaust.

This wouldn't be an issue because it runs absolutely smoothly, but after i start it and then drive without giving it at least five minutes to warm up it stalls. I don't like it when it stalls which is why im coming to you guys to see if anyone had an idea of what it could be. La ter on today I was gonna vacuum gauge the carb to make sure eveything's right. I might also do a timing check with a light or something. Or is this normal? It does however take a while to run up to eighty or ninety on the freeway, and it has trouble with uphills but I think that's my tranny it might need a rebuild because it takes quite a while to shift from first, i can tell it holds on to that gear for quite a while cause once it lets go the car gets a nice speed boost. Any help is great. Thanks guys.

I'm a lill embarrassed to answer cuz I'm such a newbie but here's some info.
Or is this normal?
Is not normal
I got the 'feed back' on a '68 170. W/ the Carter YF (sounds similar) it takes one tap to the floor before turnin the key. Starts every time (I don't use that procedure in the summer if I don't wanna set the choke). The choke will release @ about 3 min. I'm really happy since the rebuild. Always start w/the sm/simple/cheep stuff like fuel filters, is it clean gas, etc, no?

 

[ludwig]

You can make sure you have the engine adjusted more or less properly with the vacuum gauge. Hook it up to a manifold (not carb) vacuum port. Usually there is one right below the carb on a brass block. If you have it adjusted right, the vacuum will read a steady 18* or more. Minimum vac is 18*. Adjust the distributor until you have the highest possible steady vacuum you can get.

When you get this, then adjust the air/fuel mix for the idle. That is the screw next to the choke mechanism. Turn it clockwise (tighten) until the engine starts to stumble. Then back it off until you get the highest possible vac reading above 18* and then loosen it a scant 1/4 turn more. If the idle seems a little fast at this point, you can back it off to an acceptable speed at the idle speed screw. Similarly, if it is slow, step it up some. Idle with an automatic is set in Drive and needs to be 700 to 750 RPM. Stick shift is lower, 550 or so I believe (don't know exactly).

This will get a pretty good approximate idle timing. You want to use a light and dwell tach to get the real close setting. When I installed the Pertronix, the idle rpm went up quite a bit. Also, you are burning the fuel much more efficiently with EI, so you may be getting a rich condition at idle and you are flooding until it warms up all the way. Taking all these factors together, you have to tweak the idle and the A/F mix.

 

[dudeigota66]

Where exactly would i hook up the gauge? Beneath the carb on the plate theres two connections, one for the manual tranny and the other is for something else that i cant seem to remember right now, would i hook it up there? Also i saw some mention of a PCV valve on the classic inlines tech page. Where would this be if i have the Holley replacement carb? Would it be this piece by the water pump with a hose connected from the vacuum advance and another connected to the carb? Which one should i use?

 

[ludwig]

There is usually a brass plug on the intake manifold with a couple nipples. One of them is blocked off on mine. That's the one I use.

You could pull off the spark advance hose to the distributor since you are setting the idle, not the fast cruise. There is the auto tranny modulator nipple - but you have stick. There is the power brake nipple but you probably have manual brakes. You could use the nipple at the base of the carb, but the manifold port is the better one.

As for the PCV valve, which has nothing to do with idle IFAIK should be stuck on the top of the valve cover and run underneath the air filter cover.

 

[dudeigota66]

Oh sorry about that i meant to say auto nipple, i have the c4. But anyways im gonna hook it up to the nipple right next to the tranny vacuum, is that a good spot?

 

[JackFish]

There should not be any "open" nipples.
You should have to unplug something to hook in, or use a "t" to splice in.

 

[dudeigota66]

Everything seems to be connected right now, im gonna plug it into the vacuum right next to the auto tranny vacuum, or should i plug it into the tranny plug? Basically i see five vacuum lines one running from the advance tip to the valve atop the water pump another running from the round part of the advance to the carb, another running from the valve atop the water pump to the nipple by the tranny plug, and then the other line running from the intake to the tranny. Where would be the best place?

 

[ludwig]

Any one of those below the carb. Like I said, it's a block. Off the front is the tranny modulator vacuum. Off the carb is the distributor advance. I have two free: one for power brake and one for something else. Vacuum windshield wipers or something.

I am not familiar with the Holly but there has to be some vac hose that you can pull out. If you have the metal tranny modulator line, it may have a rubber connector that you can open. Then put the vac gauge on it.

Where have you been putting the vac gauge up to now?

 

[JackFish]

That's interesting, the one on the front of my manifold tee goes to my brake booster.

 

[dudeigota66]

This is the very first time i have ever tried to vacuum tune a car. Ive never even messed with a carburated engine before which is why im asking about everything. Thanks for that . But any ways, Ive been reading about putting this in a manifold vacuum but i dont know what that is.

 

[JackFish]

Manifold vacuum is any source that is below the throttle plates on the carb. Some are on the carb itself, and others come off that tee with the nipples. It's on the "intake manifold". Carbs also have vacuum ports that are above the throttle plates, and these are called "ported" vacuum sources.
The major difference between them is that manifold sources pull a vacuum at idle, and ported sources do not.

 

[dudeigota66]

Oh! Alright, sweet. So if i hook the gauge up to the auto tranny nipple id be good?

 

[ludwig]

What I'm tellin' ya.

 

[anotherhassel]

When I had my autolite on my car it would take a while to get to 90 and it wouldnt pass 90. UntilI swapped out for th dual out header and the weber carb. So in my caes the speed thing was norm. my timing was set pretty much by ear. I would just turn the dizzy to where the engine idled the highest. Then adjust carb and go for a ride. If it pinged I just backed the timing off a bit til the pinging was gone. Good luck and let us know how you make out.

 

[dudeigota66]

Alright will do.

Hows the Weber treating you as far as MPG and the Hood clearance issue? Did you use an adapter or did you do the conversion?

 

[anotherhassel]

Not sure how the mpg is but the performance is nite and day over the autolite. I am using the adapter with no clearance issues and i guess if I could keep my foot out of it it would get better mpg lol. Between the performance and the exhaust note I am having major arguments with my right foot. I also want a t5 for even more giddy up. You can check out my setup in the eye candy section. I would post a link but I dnt know how lol.

 

[dudeigota66]

I decided that it would be better for everything if i just left the Holley be and put on the 1100 from my old block. I did it in about five minutes and bam, turned it on clean without pressing the pedal. The choke is set, it has a little miss at idle and it shakes some still but not even half of what it used to. It runs smooth, so smooth. I am very satisfied with everything and indeed there's a world of a difference. Im gonna check out the Holley later on when i get more into carburetor engineering but as for now im gonna do a vacuum gauge check on the carb to get everything fine tuned and set. Im gonna try and get the tuning done today or monday, i think im gonna make a trip to the auto parts store and borrow a gauge from them to do the job today. Im feeling pretty determined right now.