Rebuilt Autolite 2100 swapped in-won't idle < than 1100 RPM

[62Ranchero200]

It does seem like a good idea to call the supplier and tell them of your problem. Sounds like they screwed up on the rebuild.

IF you do wish to continue tackling the problem, the float level needs to be adjusted properly. I found another link for you. There are good pics and a good right up on how to set the float here, but it need to be done properly.

http://www.therangerstation.com/tech_li ... 0_carb.pdf

Also, did you try to run the engine with the top off the carb and verify what is happening with the fuel level? It is a simple test and would give you a good idea of what is going on. If the fuel level is rising and flooding the carb out there is a problem with the needle and seat, or your fuel pump has failed to regulate and is over pressurizing the bowl. The needle and seat will not contain the pressure if the regulator has failed.

Thank you for the link!

I e-mailed the supplier - waiting for a response.

The engine has the stock 200 mechanical fuel pump - is there really any chance that is over-pressuring the needle valve? The Holley 1946 1V that was on the engine before never flooded out - if the stock fuel pump was over-pressuring, it seems that carb would have had the same issue. There is no external pressure regulator - should there be one? If you think that's really a possibility, I could get a fuel pressure gauge and mount it inline.

Thanks for your help,
Bob

 

[First Fox]

If you verify that the float is set correctly and the float bowl is still flooding than yes you should check the fuel pressure. My factory pump internal regulator failed and was seriously over pressurizing the carb. It just started flooding out of nowhere while driving and I couldnt tell untill I stopped at a red light and the engine would barely run. Wouldn't idle but would cruise okay. The thing started pumping so hard there was no way the needle could hold it and it needed replacement. Pulled into a parking lot and diagnosed the problem, bought a new stock fuel pump and it cured the problem.

But one thing at a time. Ya gotta set the float level correctly. Also after re-reading your post, you should not be bending anything on the float itself, but the tab that is directly over the needle.

 

[62Ranchero200]

If you verify that the float is set correctly and the float bowl is still flooding than yes you should check the fuel pressure. My factory pump internal regulator failed and was seriously over pressurizing the carb. It just started flooding out of nowhere while driving and I couldnt tell untill I stopped at a red light and the engine would barely run. Wouldn't idle but would cruise okay. The thing started pumping so hard there was no way the needle could hold it and it needed replacement. Pulled into a parking lot and diagnosed the problem, bought a new stock fuel pump and it cured the problem.

But one thing at a time. Ya gotta set the float level correctly. Also after re-reading your post, you should not be bending anything on the float itself, but the tab that is directly over the needle.

I read your PDF - very informative. However, there are some slight differences between the carb in the PDF and my carb. My needle is just a metal cylinder, it doesn't have the float retaining clip that goes over the float tab in the PDF. I was bending the metal around the float in the wrong place - I'll work on bending it back, using a dry float adjustment instead of trying to adjust the wet level.

Didn't even realize that mechanical fuel pumps had internal pressure regulators - how would I know what the line pressure to the carb is supposed to be? Also, it seems that the mechanical fuel pump would be more likely to overpressure at high RPMs, when it's being driven faster, rather than at idle. That said, you're description of your flooding problem sounds a lot like mine - flooding out of nowhere, won't idle but cruises OK. I'm skeptical of this though because there wasn't a problem until the Autolite 2100 was installed.

Thanks for the help
Bob

 

[First Fox]

It could be that the fuel pump has been over pressurizing for a while and that your other carb just tolerated the higher pressure due to a better needle and seat, or some other reason and this is why the problem appeared when you installed the 2100. Again we are assuming this new carb is rebuilt and set up properly.

The fuel pump pressure would be available in a print manual, or online and a number in the ballpark would be good enough I imagine. Seems to be that around 7 psi should be max, but I am not sure. I know on my Webers it is 3.5 psi and even as little as 4.5 psi will flood it, but any Holley I have owned ran fine @ 8 psi, and adjusting the external regulator 1.5 psi either way didn't bother those carbs one bit.

The 2100 design allows the advantage of running the engine while the top is off and verifying what is happening. This is impossible on most other carbs and makes troubleshooting the problem easier. 8)

BTW, is your carb mounted with the throttle shaft parallel to the crankshaft, or perpendicular?

 

[bubba22349]

I can still see gas droplets dripping down ONE venturi booster. I can't understand how a high bowl level or any other condition would cause gas to drip out of only ONE venturi booster.

This is likely from a loose or bad Power valve, or it's gasket.

 

[62Ranchero200]

It could be that the fuel pump has been over pressurizing for a while and that your other carb just tolerated the higher pressure due to a better needle and seat, or some other reason and this is why the problem appeared when you installed the 2100. Again we are assuming this new carb is rebuilt and set up properly.

The fuel pump pressure would be available in a print manual, or online and a number in the ballpark would be good enough I imagine. Seems to be that around 7 psi should be max, but I am not sure. I know on my Webers it is 3.5 psi and even as little as 4.5 psi will flood it, but any Holley I have owned ran fine @ 8 psi, and adjusting the external regulator 1.5 psi either way didn't bother those carbs one bit.

The 2100 design allows the advantage of running the engine while the top is off and verifying what is happening. This is impossible on most other carbs and makes troubleshooting the problem easier. 8)

BTW, is your carb mounted with the throttle shaft parallel to the crankshaft, or perpendicular?

The carb is mounted with the throttle shaft parallel to the crankshaft. That's how the CI adapter is designed, and I would think that's better for fuel distribution.





Going to pick up an inline fuel pressure gauge so that I can either rule out or confirm acceptable fuel pressure.

UPDATE: The carb vendor replied and told me that the wet fuel level should be 7/8" below the top of the bowl! That's much lower than the level I observed before I adjusted the float. Also, he says that the expected fuel pressure is 5.0 - 6.5 PSI. He advised me to adjust the float, take the needle out and clean it, making sure there's no trash on the needle or in the valve.

Thanks
Bob

 

[62Ranchero200]

It could be that the fuel pump has been over pressurizing for a while and that your other carb just tolerated the higher pressure due to a better needle and seat, or some other reason and this is why the problem appeared when you installed the 2100. Again we are assuming this new carb is rebuilt and set up properly.

The fuel pump pressure would be available in a print manual, or online and a number in the ballpark would be good enough I imagine. Seems to be that around 7 psi should be max, but I am not sure. I know on my Webers it is 3.5 psi and even as little as 4.5 psi will flood it, but any Holley I have owned ran fine @ 8 psi, and adjusting the external regulator 1.5 psi either way didn't bother those carbs one bit.

The 2100 design allows the advantage of running the engine while the top is off and verifying what is happening. This is impossible on most other carbs and makes troubleshooting the problem easier. 8)

BTW, is your carb mounted with the throttle shaft parallel to the crankshaft, or perpendicular?

Installed an inline fuel pressure gauge - fuel pressure is 5.5 - 6 psi at idle (keeping in mind that my idle is higher than normal ATM). So I would say the pump isn't overpressuring the needle valve.

Set the float level properly according to the rebuild instructions - 7/16" dry float setting (from the toe of the float to the gasket surface on the bowl). Then I left the top off, but put a small piece of glass from a photo frame on top of the carb. This let me see the float level, while giving me at least some protection from gas spilling onto the headers below. The fuel level stayed about 1/2" below the gasket surface on the bowl, which I think is how it was before I first adjusted the float. However, occasionally the engine RPMs go down as the engine tries to die. At those times, the engine shakes so badly that gas is sloshed onto the underside of the glass. This is undoubtedly the same as when I see gas coming out of the vent hole on the carb top. Not overflowing, just sloshing violently. I don't think float level or needle valve are causing my issues.



Gas droplets are still dripping from the back venturi booster, and the engine still idles very roughly.

The only other thing I can think of is the power valve - maybe it leaks or isn't closing from vacuum as it should?

Thank you,
Bob

 

[First Fox]

That sucks. Sorry to have you chasing shadows man. I was basing my suggestion on the fact that the carb was rebuilt correctly, perhaps that was a bad idea. It seemed to me that the float level could have been misadjusted for your car due to all the different applications for a given carb. It could be a bad power valve, but if you have a newly rebuilt carb with a bad PV, or one with a missing PV gasket or something like that, then this thing was rebuilt by someone with out a clue and you are probably going to have to end up going through the whole thing again.

I would look toward the power valve at this point. The writeup I sent you should explain the replacement pretty well. Again these are pretty simple carbs.

BTW, how much vacuum is your engine pulling @ idle? You said you had a replacement cam, is it lopey at all? It is a possibilty that the idle vacuum is below what is required to keep the PV closed, but was alright with the old carbs PV rating. In other words if you were sold an economy carb that may have a PV with a rating of 10 inches of vacuum, and your idle is at 9 due to your cam profile or another problem, the powervalve will not close even if the valve is perfect. Perhaps the one in your old carb was of a lower rating (say 7 inches) and it gave you no problems because of this reason. If this is the case you can buy a PV with a lower vacuum rating.


Again sorry for the ghost chase man, just trying to help.

 

[62Ranchero200]

That sucks. Sorry to have you chasing shadows man. I was basing my suggestion on the fact that the carb was rebuilt correctly, perhaps that was a bad idea. It seemed to me that the float level could have been misadjusted for your car due to all the different applications for a given carb. It could be a bad power valve, but if you have a newly rebuilt carb with a bad PV, or one with a missing PV gasket or something like that, then this thing was rebuilt by someone with out a clue and you are probably going to have to end up going through the whole thing again.

I would look toward the power valve at this point. The writeup I sent you should explain the replacement pretty well. Again these are pretty simple carbs.

BTW, how much vacuum is your engine pulling @ idle? You said you had a replacement cam, is it lopey at all? It is a possibilty that the idle vacuum is below what is required to keep the PV closed, but was alright with the old carbs PV rating. In other words if you were sold an economy carb that may have a PV with a rating of 10 inches of vacuum, and your idle is at 9 due to your cam profile or another problem, the powervalve will not close even if the valve is perfect. Perhaps the one in your old carb was of a lower rating (say 7 inches) and it gave you no problems because of this reason. If this is the case you can buy a PV with a lower vacuum rating.


Again sorry for the ghost chase man, just trying to help.

If I remember correctly, I have 15" of manifold vacuum at my relatively high idle. The cam is slightly lopey, but not too much (Clay Smith 264/264/110 hydraulic).

Is there any way to temporarily disable to power valve to test whether it is causing the idle issue?

Thanks for your help,
Bob

 

[First Fox]

I am not aware of any way to disable the powervalve since the passages are all internal. Some racers plug the PV and they re-jet accordingly.

The only way I know of to help diagnose the powervalve is to start it up and turn both of the idle mixture screws all the way in. If the engine dies, the PV is working properly and is closed at idle. If it the engine remains running at that point, it is doing so from the fuel in the PV circuit and it means that the PV has either failed or is the wrong rating for your idle vacuum. Who knows what PV your rebuilder put in it. And again, this is assuming that you are idling at a low enough speed and is indeed running on the idle circuit.

 

[62Ranchero200]

I am not aware of any way to disable the powervalve since the passages are all internal. Some racers plug the PV and they re-jet accordingly.

The only way I know of to help diagnose the powervalve is to start it up and turn both of the idle mixture screws all the way in. If the engine dies, the PV is working properly and is closed at idle. If it the engine remains running at that point, it is doing so from the fuel in the PV circuit and it means that the PV has either failed or is the wrong rating for your idle vacuum. Who knows what PV your rebuilder put in it. And again, this is assuming that you are idling at a low enough speed and is indeed running on the idle circuit.

Happy 4th! Thanks for continuing to give me input.

Pulled the cover off of the power valve, and there was no gas inside the cover. If I understand correctly, this means that the diaphragm inside the PV is still intact (not leaking).

The PV had "75" stamped on the flat accessible from outside the carb, which I understand to mean that the power valve opens below 15" of vacuum.

What is the expected manifold vacuum at idle for a stock 200, is it consistently above 15"? My 200 pulls almost exactly 15" of vacuum at idle, probably because of the aftermarket cam (and maybe also because my DS II has worn shaft bushings and needs replacement). So, with a rating of 7.5 this PV could be opening at idle. I'm thinking I should try a PV with a lower rating. Summit Racing has power valves all the way from 1 (opens below 2") to 6.5 (opens below 13"). I could also order a power valve block-off, so that I could temporarily block off the PV only for troubleshooting purposes. If blocking off the PV doesn't improve the over-rich condition, then the PV is obviously not the problem and I don't need to continue troubleshooting that.

Other than the PV, the only other strategy that occurs to me is to gradually lower the float level to see if that improves the situation. It's very hard to guess how float level affects the mixture of the idle and main circuits. I suppose there could be crack deep inside the carb casting that's impossible to see from the outside. I don't see how anyone could ever diagnose that.

Thanks
Bob

 

[JackFish]

I seem to recall wsa111 had a 6.5 power valve in his 2bbl, but it's a 500cfm Holley.
He also put some .010 guage wire in the idle circuit. I think.
He did some tuning with a wide-band and got his carb dialed in.

 

[Frankenstang]

It's very hard to guess how float level affects the mixture of the idle and main circuits.

Fuel is fed to the venturi of a carburetor by a prescribed/designed ratio of vacuum to fuel inlet. Whether it is the main (jet) fuel circuit or idle (an adjustable air/vacuum bleed) fuel circuit the feed is a carefully ‘calibrated’ ratio of vacuum (neg pressure) to fuel inlet/feed.

From a FSM, “The fuel inlet system of the carburetor maintains a predetermined fuel level in the fuel bowl. The fuel level in the bowl is extremely important to carburetor calibration. If the level of the fuel in the bowl is below the specified setting, a lean fuel-air mixture will result [feeding less fuel at each point in the pressure/vacuum range].
A rich fuel-air mixture will occur from a higher than specified fuel level [feeding more fuel at each point in the pressure/vacuum range]. The entire calibration of the carburetor is disturbed if the fuel level is not set as specified.”
http://falconfaq.dyndns.org/display1.ph ... age=10-008

Happy 4th :USA:

 

[69.5Mav]

One of my sons friends rebiult his two barrel autolite off his 302 maverick engine. They spent all day tring to get it to idle and failed.

The next day I worked on it and found that a perfectly good power valve was dripping fuel with the carb off the engine. I reinstalled the "old" power valve and the problem was solved.

The upshot is that you could pull the carb and with a full fuel bowl look to see if the carb is leaking fuel.

Good luck.

 

[62Ranchero200]

I am not aware of any way to disable the powervalve since the passages are all internal. Some racers plug the PV and they re-jet accordingly.

The only way I know of to help diagnose the powervalve is to start it up and turn both of the idle mixture screws all the way in. If the engine dies, the PV is working properly and is closed at idle. If it the engine remains running at that point, it is doing so from the fuel in the PV circuit and it means that the PV has either failed or is the wrong rating for your idle vacuum. Who knows what PV your rebuilder put in it. And again, this is assuming that you are idling at a low enough speed and is indeed running on the idle circuit.

Have ordered the #65 power valve and a PV block-off from Summit Racing. In the meantime, have done the following:

Disassembled the carb except for the automatic choke, throttle plates and throttle lever to check for cracks or other damage (found none). Idle mixture screws were not damaged.

Blew carb cleaner through all of the passages at high pressure.

Verified that the venturi booster gasket was present, the accelerator pump check ball was present and the weight inside the hollow venturi boosters screw.

Removed the jets and verified that they are the same size (#46) and not obstructed.

Will try the #65 PV first; if that doesn't resolve, will try the PV block-off next.

Bob the Builder

 

[First Fox]

I have no idea what you paid for this rebuilt carb, but it was too much. OR, the price was very reasonable considering you now know how to rebuild one yourself.

I hope the PV solves your problem. Please keep us posted!

 

[jahearne]

Learning about carburetors the hard way!

It's fustrating but I can appreciate your efforts. I first carb experience was with a Holley 1904 tri-power. I too bought a carb from Gotta Fish, a 1.08; he's a good vendor and I feel that he would not purposely try to screw someone. My carb had the same issues as yours. Trying to set the wet float level is one heck of challenge with a rough running motor!

I'm running a 274* cam with ClassicInine 2V conversion. Upgrading to 50 jets and setting the float level at 3/8" wet is what worked best for my setup. I had to use a pressure regulator and eventually, I bent the metal tab on the float to give it more leverage (make it longer, think seasaw). Then I was able to open up the pressure regluator all the way. But that didn't fix the fuel dripping down the venturi. I had a heat sink problem; the gas was literally boiling out of the carb. Finally, minimized that problem (nearly eliminated it) by swapping out the aluminum 2V adaptor for a 1/2" phenolic one and using a thick 3/8" gasket.

Hang in there!

 

[62Ranchero200]

Learning about carburetors the hard way!

It's fustrating but I can appreciate your efforts. I first carb experience was with a Holley 1904 tri-power. I too bought a carb from Gotta Fish, a 1.08; he's a good vendor and I feel that he would not purposely try to screw someone. My carb had the same issues as yours. Trying to set the wet float level is one heck of challenge with a rough running motor!

I'm running a 274* cam with ClassicInine 2V conversion. Upgrading to 50 jets and setting the float level at 3/8" wet is what worked best for my setup. I had to use a pressure regulator and eventually, I bent the metal tab on the float to give it more leverage (make it longer, think seasaw). Then I was able to open up the pressure regluator all the way. But that didn't fix the fuel dripping down the venturi. I had a heat sink problem; the gas was literally boiling out of the carb. Finally, minimized that problem (nearly eliminated it) by swapping out the aluminum 2V adaptor for a 1/2" phenolic one and using a thick 3/8" gasket.

Hang in there!

Jahearne,

Are you running a 200 or a 250?

Haven't had time to work on this since Friday because my first grandchild arrived over the weekend , then I had a medical appointment yesterday morning.

Since I have about 15" of vacuum at idle, and my 1.02 came with a #75 power valve, I'm thinking that that power valve may be opening up at idle, enriching the mixture too much. I'm going to swap out the power valve for #65. If that doesn't do it I'm going to temporarily block the power valve to see if that helps (I won't leave it blocked, if that helps will keep lowering the power valve # until the carb no longer runs rich).

If I could find one of those thick gaskets I would use one, but so far no luck. ATM I'm using a FelPro gasket, high quality, but less than 1/8" thick.

Thanks
Bob

 

[62Ranchero200]

I have no idea what you paid for this rebuilt carb, but it was too much. OR, the price was very reasonable considering you now know how to rebuild one yourself.

I hope the PV solves your problem. Please keep us posted!

Finally got back to the Ranchero this week after the new grandchild and eye surgery.

Installed the #65 power valve and also found an application specific float level guide by year and engine size. For my '62 vintage 2100, that came out to 21/32 dry float level. Carburetor re-installed, the engine idles incrementally smoother, but still not as well as I would like (will idle well in park and roughly in gear, once it has warmed up; difficult to drive without stalling until warmed up).

I have come around to believing that the engine is running lean at idle, because closing the choke plate by hand still makes it run more smoothly and at higher RPMs, especially when cold. Moved the PVC connection from manifold vacuum to the air cleaner, which I believe should make it run a bit richer (PVC is essentially a small, controlled vacuum leak, right?). Am probably going to adjust the choke plate position re: the choke shaft to be a bit richer (close the choke plate a bit). Have not been able to find a thick carb gasket so far. Mike's carburetor parts has one, but oddly enough it has cutouts where the carb studs go; if the carb mounting nuts are overtightened slightly, the lack of support underneath could cause the carb base to crack.

I'm sure some of the rough idle is ignition related (DS II has bushing wear), so in the near future I will turn to addressing that.

Thanks
Bob the Builder

 

[First Fox]

Good to see you are still at it man. I believe a rebuilt DS2 distributor will only run about 30 40 bucks and would be a good investment at this point if you know it is shot anyway. Drop it in and see if it help the idle enough that you can live with it.

Now if you are still seeing raw fuel AND you can improve the idle by hand choking the engine, that would probably indicate you are running lean in a major way. Try looking for a vacuum leak that would have been carb swap related, mainly the adapter, gaskets etc. Get her running at best idle and spray the adapter plate with small shots of carb cleaner and see if the idle improves. Disconnect and block off all vacuum lines while doing this to eliminate that as a possibility, (except the distributor as the loss of advance would only make it run worse) and hook them back up one at a time. If the idle worsens when a given line is reconnect, then that will need to be explored. (leaky PCV valve, brake booster, heater control etc).

Good luck!