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| Slant six running rough/lean and not performing right. SOLVED!! https://slantsix.org/forum/viewtopic.php?t=63294 |
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| Author: | matv91 [ Sun Feb 17, 2019 1:08 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
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| Author: | matv91 [ Sun Feb 17, 2019 1:36 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
In the black circle is where main jet goes,behind it is idle fuel feed tube. Green is fuel supply to main system air well. Make sure its open. White is cross connection between air well and main. There are sealed ,leave alone. |
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| Author: | matv91 [ Sun Feb 17, 2019 3:19 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
could the idle air bleed hole really be that much too big. Yes, my 1920 carbs still in good shape not rebuilt have brass insert in idle air hole. Some not in good shape the insert is gone, just a big hole. After market rebuilt ones the idle air hole is just plugged solid. Some 1971 1972, 1920 carbs the size of idle air bleed was adjusted with a screw and then sealed. |
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| Author: | matv91 [ Sun Feb 17, 2019 5:11 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
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| Author: | matv91 [ Sun Feb 17, 2019 5:26 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
The hole inside the black circle contains the idle air adjustment screw |
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| Author: | matv91 [ Sun Feb 17, 2019 6:18 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
More idle thoughts. 1966 carb set up for use with 1966 gas, camshaft, pcv valve and correct valve adjustment,and non worn throttle shaft or other vacuum leaks. All this could affect idle system. Low fuel level in bowl means ,fuel level in idle draw tube and accelerator pump well is also low. |
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| Author: | JukkaK [ Sun Feb 17, 2019 9:04 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
Quote: In the black circle is where main jet goes,behind it is idle fuel feed tube. Green is fuel supply to main system air well. Make sure its open. White is cross connection between air well and main. There are sealed ,leave alone.
I'll make sure it's open.Quote: could the idle air bleed hole really be that much too big. Yes, my 1920 carbs still in good shape not rebuilt have brass insert in idle air hole. Some not in good shape the insert is gone, just a big hole. After market rebuilt ones the idle air hole is just plugged solid. Some 1971 1972, 1920 carbs the size of idle air bleed was adjusted with a screw and then sealed.
Why would the plug the idle air hole shut? Or is that what you mean?
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| Author: | JukkaK [ Mon Feb 18, 2019 7:51 am ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
I installed a size 60 jet in there just to see what it'll do, again it got a bit better but still not smooth. With the size 60 jet acceleration is a lot more "stable" and responsive but I still am not able to punch it to the floor, it feels like it'll die but then all of a sudden the engine responses to that and accelerates. With the carb in the car and float in place I wasn't able to see that tiny hole that feeds fuel to the main system airwell, have to wait till the weekend. I will also check if the timing chain is worn because it might cause false readings on the ignition timing. I currently have it at 12 degrees BTDC, if I retard it from there it'll gets worse performance wise. Oh and I'll also check the fuel level at the bowl by doing that wet measurement. One thing I wonder is how much the float bowl vent valve adjustment matters? It says in the manual that, at the curb idle, a 0.0937 inch drill bit should be able to fit in between the valve and the valve seat and the gap should never exceed 0.125 inches. It doesn't say why in the manual. Anyway I had a way way waaay over 0.125 inch gap in between the bowl vent valve and seat. I now set it closer to the spec. I mean what does it matter if the gap is too big? |
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| Author: | THOR [ Mon Feb 18, 2019 1:53 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
When you are setting base timing, you have the vacuum advance disconnected right? ~THOR~ |
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| Author: | JukkaK [ Mon Feb 18, 2019 8:31 pm ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
Quote: When you are setting base timing, you have the vacuum advance disconnected right?
Yes, I have the vacuum advance disconnected when I set the timing. And also I have tried many different timing settings.~THOR~ One thing though, I checked the vacuum advance system by applying vacuum with a hand held vacuum pump. It responses to vacuum but not instantly, actually it needs quite a bit of vacuum to get that vacuum advance to work (about 17 - 18inHg or 0,6 bar absolute pressure). And when manifold vacuum drops at the moment when the throttle plate is being opened at low rpm, I'm not sure if the vacuum is enough to operate the vacuum advance system. In the manual it says that the vacuum advance system should respond immediatly when applying vacuum with the hand held pump... like I said, mine does not. |
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| Author: | JukkaK [ Tue Feb 19, 2019 8:22 am ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
Update Now that I put the size 60 jet in the carb I thought that I'll take the idle airbleed restriction, I installed earlier, out and set the idle mixture (only by ear for now) and do some testing with the ignition timing. I set the ignition timing at 5 degrees BTDC. To my surprise the car is working perfectly at the highway at light throttle and the stumble when accelerating hard is WAY smaller. It still isn't perfect at low rpm, light load (light throttle) situations and it has a tiny bit of hesitation when trying to accelerate from low rpm. I also checked the fuel level in the bowl by measuring from the economizer hole. It is kinda hard to measure it that precisely because my engine mounts are very worn and the engine shakes a bit. But from the outer surface of the economizer hole to the fuel the distance is about 26/32 inches, this is the right way to measure it, right? |
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| Author: | drgonzo [ Tue Feb 19, 2019 8:29 am ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
I suspect the carburetor is performing better and a bit more timing might eliminate the stumble all together. 8-10 BTDC. |
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| Author: | JukkaK [ Tue Feb 19, 2019 8:45 am ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
Quote: I suspect the carburetor is performing better and a bit more timing might eliminate the stumble all together. 8-10 BTDC.
Actually, I went from 12 BTDC to 5 BTDC. It was way worse at 12 but when I had the size 58 jet in there it was best at 12 BTDC. The idle is also very smooth at 5 BTDC now with the size 60 jet, if I'll move up from there the idle will start to get a bit misfireing/uneven.
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| Author: | drgonzo [ Tue Feb 19, 2019 8:48 am ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
That's interesting. Makes me think the timing marks may be off a bit. |
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| Author: | JukkaK [ Tue Feb 19, 2019 8:56 am ] |
| Post subject: | Re: Slant six running rough/lean and not performing right. |
Quote: That's interesting. Makes me think the timing marks may be off a bit.
You mean the plate which has the 15 - 0 scale in it and the mark in the damber? How could they be off? Could the mark in the damber maybe move somehow? The damber seems fine to me, there's no sings of breakage in it or anything like that. Maybe someone has installed the timing gears and chain one tooth off, don't know.
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