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

[62Ranchero200]

Just installed a rebuilt Autolite 2100 2V on my 200 using the 1V-2V adapter from CI. The
Autolite is a 1962 vintage 1.02 ( = 245 CFM), complete with automatic choke. I used a new inline fuel filter (screws into the fuel fitting on the carb), a lokar throttle cable, and a homemade throttle cable bracket.

To give a bit of background, it's a recently refreshed '79-80 200, stock bottom end, Large log
head with pocket porting, Clay Smith 262H cam, DuraSpark II with wear issues (soon to be
replaced), and Pacemaker headers. With the old carb (an emissions Holley 1946 1V), the 200 idled well enough, although there was some roughness in the idle (I think partly due to the cam, and partly to distributor bushing wear). Once warm, the engine would never die at idle with the Holley. The same gas, fuel pump, and fuel lines are in the car now.

With the Autolite 2100, the engine seems to cruise, rev, and accelerate well, but won't idle any lower than about 1,100 RPM. If I set the idle any lower than that, the engine will idle for a short time, then stumble and die.

Have done the following so far:

Checked the timing without vacuum advance: 12 degrees initial advance, as I expected
With the vacuum advance connected, timing is being advanced as I expected
Adjusted the idle mixture screws (there are two of them), no discernable difference
Opened the choke plate by hand, in case the engine needed more air at idle - no difference

The only possible cause that occurs to me is the idle passages are clogged with a foreign particle. If the power valve wasn't getting vacuum for some reason, and so was stuck open, could that cause an inability to idle?

Note: seems to idle a little smoother if I leave a vacuum line disconnected, allowing a small vacuum leak.

Thank you,
Bob the Builder

 

[First Fox]

When you say the carb was rebuilt, does that mean from a reputable manufacturer or a guy you bought it from on Craigslist or did you do it yourself? If it were done properly the power-valve should be fresh and there wouldn't be any trash in any of the circuits. If someone did a questionable job on a rebuild and only replaced a few gaskets so it didn't leak, you could have any number of problems. If that is the case and the power-valve is blown then yes it will idle like shit. Try to introduce a vacuum leak by disconnecting a vacuum line while it is idling as low as possible. If you notice any difference in the idle speed that would indicate a rich condition and certainly could be a faulty power-valve. Also try to placing your hand over the choke horn to restrict the air and see if the idle speed raises. That would indicate a lean condition and is probably due to a vacuum leak. A bad fitting gasket at the adapter could be to blame there.

It could also be a float level set too high. Are you familiar with how to set that?

 

[62Ranchero200]

When you say the carb was rebuilt, does that mean from a reputable manufacturer or a guy you bought it from on Craigslist or did you do it yourself? If it were done properly the power-valve should be fresh and there wouldn't be any trash in any of the circuits. If someone did a questionable job on a rebuild and only replaced a few gaskets so it didn't leak, you could have any number of problems. If that is the case and the power-valve is blown then yes it will idle like doggie doo. Try to introduce a vacuum leak by disconnecting a vacuum line while it is idling as low as possible. If you notice any difference in the idle speed that would indicate a rich condition and certainly could be a faulty power-valve. Also try to placing your hand over the choke horn to restrict the air and see if the idle speed raises. That would indicate a lean condition and is probably due to a vacuum leak. A bad fitting gasket at the adapter could be to blame there.

It could also be a float level set too high. Are you familiar with how to set that?

Carb was rebuilt by the EBay vendor. Apparently, the vendor specializes in restoring Autolite carbs, has been in business doing so for many years, and has many positive reviews from EBay customers. Of course, all of this could probably be faked if someone wanted to go to such lengths.

I've already tried disconnecting a vacuum line and it seems to idle a little smoother when doing so. Will try closing the choke plate a bit to see how that affects the idle.

Have not set a float level before, but for starters I could simply take the top off the carb (with the carb still on the engine, but the engine off) and visually check the fuel level, right?

Thanks for your help,
Bob

 

[First Fox]

Sorry I missed you writing that you tried the vacuum leak already. That means a rich condition of course and could be a float that's a bit high. Below is a link to a pdf file that I used to rebuild my first 2100 series carb and it was very helpful. Gives some good tuning tips for a fresh carb setting the choke, pull-off and idle speeds etc. along with pics for setting the float. The float would be a great place to start. If your carb is fresh, it wont even cost you a gasket, as long as you are careful taking the top off.

www.therangerstation.com/tech_library/. ... 0_carb.pdf

 

[170-3tree]

What vendor did you get the carb from? I got one on eBay and basically had to rebuild it again to get some kinks worked out. The float was way to high with the wrong type of needle and one of the idle needles was mauled up a bit more than it should be. It caused a few problems to say the least.

 

[62Ranchero200]

Sorry I missed you writing that you tried the vacuum leak already. That means a rich condition of course and could be a float that's a bit high. Below is a link to a pdf file that I used to rebuild my first 2100 series carb and it was very helpful. Gives some good tuning tips for a fresh carb setting the choke, pull-off and idle speeds etc. along with pics for setting the float. The float would be a great place to start. If your carb is fresh, it wont even cost you a gasket, as long as you are careful taking the top off.

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

Couldn't access the link at this time - something about updating the site.

Pulled the top off of the carb tonight. The float doesn't have any gas in it, doesn't have any holes and seems to float as it should. When I first pulled the top off, the gas level was about 3/8" - 1/2" below the top of the bowl. The needle valve moves freely. I don't really see how a high level in the bowl would cause a rich condition - looking at it with the top off, it seems that it would just overflow out of the vent on top of the middle of the bowl.

Noticed a couple of adjustments with the accelerator pump. Moved the rod up higher on the throttle lever, so that the pumping action is less for my 200 (carb was originally designed for a 292!). Also moved the other end of the rod to the outside hole on the accelerator pump arm, again so that the pumping action is less.

Also checked the timing again - it was advanced a little too much, so I corrected that.

Noticed that when I close the choke with my hand, the engine idles a little smoother.

At this point I have no theories other than an idle circuit obstruction or an issue with the power valve.

Thank you,
Bob

 

[62Ranchero200]

What vendor did you get the carb from? I got one on eBay and basically had to rebuild it again to get some kinks worked out. The float was way to high with the wrong type of needle and one of the idle needles was mauled up a bit more than it should be. It caused a few problems to say the least.

Vendor was Gotta Fish Carbs.

Thank you,
Bob

 

[JackFish]

Do the throttle plates close all the way?
Where are you connecting the vacuum, ported or manifold?
Ported off the carb will (should) give no vacuum at idle which is what a DS2 needs to see.

 

[170-3tree]

What vendor did you get the carb from? I got one on eBay and basically had to rebuild it again to get some kinks worked out. The float was way to high with the wrong type of needle and one of the idle needles was mauled up a bit more than it should be. It caused a few problems to say the least.

Vendor was Gotta Fish Carbs.

Thank you,
Bob

That's exactly who I bought from. It was a good deal and ran with the carb, but after a $20 kit, it did so much better. Still working kinks out with a vastly different engine, but its better after that.

 

[62Ranchero200]

Do the throttle plates close all the way?
Where are you connecting the vacuum, ported or manifold?
Ported off the carb will (should) give no vacuum at idle which is what a DS2 needs to see.

Yes, throttle plates close all the way. To my surprise, the spark port on the Autolite does act like ported vacuum, giving no vacuum at a normal idle and vacuum at higher RPM. Currently though, I have the idle set so high that the spark port is giving vacuum, because the engine will not idle at a reasonable RPM (say, 850-900 in park).

After I noticed that closing the choke plate by hand smooths out the idle, I'm beginning to think that it's running lean, either because of a vacuum leak, or because the choke plate wasn't adjusted properly when the carb was rebuilt. Earlier, I opened a small vacuum line and that smoothed the idle out a bit, but that came from a vacuum tap at the very front of the intake, near #1, and perhaps it smoothed out the engine because of the somewhat uneven air/fuel distribution with a log type manifold.

I'm going to pull the carb off today and check the fit between the manifold, adapter, gaskets, and carb closely. May also try adjusting the choke plate.

Thank you,
Bob

 

[62Ranchero200]

What vendor did you get the carb from? I got one on eBay and basically had to rebuild it again to get some kinks worked out. The float was way to high with the wrong type of needle and one of the idle needles was mauled up a bit more than it should be. It caused a few problems to say the least.

Vendor was Gotta Fish Carbs.

Thank you,
Bob

That's exactly who I bought from. It was a good deal and ran with the carb, but after a $20 kit, it did so much better. Still working kinks out with a vastly different engine, but its better after that.

The reason I went with a rebuilt carb is that I am not familiar with rebuilding them and not too confident I could diagnose issues. That leaves me in no man's land if there are issues with the carb.

How would I tell if the wrong needle was being used for the needle valve? What is the fuel level supposed to be in the bowl? It was 3/8" - 1/2" from the top when I took the top off. I can say that the float isn't leaking, it still floats, and the needle valve isn't stuck, but that's about it.

How would I know if the power valve wasn't working properly? Or is it inexpensive enough that I could just replace it in case?

If the idle passages were clogged, would I be able to see that? Is there a certain place through which I could blow air to unclog them?

Thank you,
Bob

 

[First Fox]

Sorry for the bad link. i will try to locate the manual somewhere else for you. It was very helpful. The float level is very important and if it is too high it will indeed cause a rich mixture. It needs to be at a predetermined level so there is a proper amount of fuel in the emulsion tubes, air bleeds and idle and main passages and you just cant see these even with the top off the carb.

Looks like you have a couple problems here. You said by introducing a vacuum leak it improved the idle, and by closing the choke plate it also improved. This is possible because the carb is no longer in the idle circuit and you will need to get the idle speed down in order to set the mixture screws and make the thing idle at all. I know, it sounds backwards if you are at 1200 rpm, there is a good chance you are not even in the idle circuit at all and would explain why the engine failed to respond to your adjusting the idle mixture screws.

I would give this a try. At 3/8 inch of gap in the bowl I would say it is a bit high. Set the mixture screws to 1.5 turns out from lightly seated. Lower the float a bit and start the engine again. You can run it with the top off of the car, keep an extinguisher handy just in case. 8) Advance the timing to where it idles the smoothest, disregard any timing marks and do it by ear for the moment. Adjust the idle down as much as possible and if needed adjust the timing for best idle. When you are able to get the idle speed in an area that is definitely in the idle circuit, try adjusting the idle mixture screws, again listen for the smoothest idle and keep the screws very close to each other in the amount of turns.

When you obtain a reasonable idle speed you can reset the timing and fine tune the mixture again.

BTW, why did you change carbs in the first place? Did you had a fuel related problem on your old set up?

 

[62Ranchero200]

Sorry for the bad link. i will try to locate the manual somewhere else for you. It was very helpful. The float level is very important and if it is too high it will indeed cause a rich mixture. It needs to be at a predetermined level so there is a proper amount of fuel in the emulsion tubes, air bleeds and idle and main passages and you just cant see these even with the top off the carb.

Looks like you have a couple problems here. You said by introducing a vacuum leak it improved the idle, and by closing the choke plate it also improved. This is possible because the carb is no longer in the idle circuit and you will need to get the idle speed down in order to set the mixture screws and make the thing idle at all. I know, it sounds backwards if you are at 1200 rpm, there is a good chance you are not even in the idle circuit at all and would explain why the engine failed to respond to your adjusting the idle mixture screws.

I would give this a try. At 3/8 inch of gap in the bowl I would say it is a bit high. Set the mixture screws to 1.5 turns out from lightly seated. Lower the float a bit and start the engine again. You can run it with the top off of the car, keep an extinguisher handy just in case. 8) Advance the timing to where it idles the smoothest, disregard any timing marks and do it by ear for the moment. Adjust the idle down as much as possible and if needed adjust the timing for best idle. When you are able to get the idle speed in an area that is definitely in the idle circuit, try adjusting the idle mixture screws, again listen for the smoothest idle and keep the screws very close to each other in the amount of turns.

When you obtain a reasonable idle speed you can reset the timing and fine tune the mixture again.

BTW, why did you change carbs in the first place? Did you had a fuel related problem on your old set up?

The 200 in the '62 was swapped in from a '79-80 Fairmont. The Holley 1946 1V idled reasonably well, but the engine seemed reluctant to rev and didn't accelerate that well, considering the other mods done (pocket porting, Clay Smith cam, headers). Also, the Holley was meant for an emissions engine with an ECM, a catalytic converter and EGR, and my '62 has none of those. I doubt I could ever be certain that the Holley was operating in an optimal way with so many vacuum taps and electrical control leads disconnected.

The Autolite should offer more top end, since it features slightly higher CFM (245 vs. 200 for the Holley), but should also offer good response since each of the venturis is relatively small (1.02). Also, it's a 1962 carb, and doesn't "expect" any emission controls or electronics that I don't have. I also understand that once dialed in, Autolites are durable.

Thanks for your help,
Bob

 

[62Ranchero200]

Sorry for the bad link. i will try to locate the manual somewhere else for you. It was very helpful. The float level is very important and if it is too high it will indeed cause a rich mixture. It needs to be at a predetermined level so there is a proper amount of fuel in the emulsion tubes, air bleeds and idle and main passages and you just cant see these even with the top off the carb.

Looks like you have a couple problems here. You said by introducing a vacuum leak it improved the idle, and by closing the choke plate it also improved. This is possible because the carb is no longer in the idle circuit and you will need to get the idle speed down in order to set the mixture screws and make the thing idle at all. I know, it sounds backwards if you are at 1200 rpm, there is a good chance you are not even in the idle circuit at all and would explain why the engine failed to respond to your adjusting the idle mixture screws.

I would give this a try. At 3/8 inch of gap in the bowl I would say it is a bit high. Set the mixture screws to 1.5 turns out from lightly seated. Lower the float a bit and start the engine again. You can run it with the top off of the car, keep an extinguisher handy just in case. 8) Advance the timing to where it idles the smoothest, disregard any timing marks and do it by ear for the moment. Adjust the idle down as much as possible and if needed adjust the timing for best idle. When you are able to get the idle speed in an area that is definitely in the idle circuit, try adjusting the idle mixture screws, again listen for the smoothest idle and keep the screws very close to each other in the amount of turns.

When you obtain a reasonable idle speed you can reset the timing and fine tune the mixture again.

BTW, why did you change carbs in the first place? Did you had a fuel related problem on your old set up?

Have done this so far:

Pulled the carb and adapter off to check for vacuum leaks. There was a film of liquid gas on the gasket surfaces, which I take to mean there were leaks at the gasket surfaces. I installed the carb with the gaskets dry - is gasket sealer normally used?

Also reviewed orientation of all components. While a quick glance might give the impression that the Autolite 2100 adapter, gasket and carb are bilaterally symmetrical (can be flipped around either way), on closer examination that is not so. The gasket only fits the adapter and carb in one orientation, with the tab away from the accelerator pump, towards the valve cover. Makes me wonder why the tab is there:



This means that the longer ears of the adapter must be on the accelerator pump side, away from the valve cover.

As I understand it, the power valve is held closed by vacuum, so it needs vacuum in order to stay closed. Looking at the adapter and gasket, the hole in the gasket, which seems to be for connecting the power valve area to manifold vacuum, is almost completely obscured by the insert on the carb adapter:



So, I enlarged the hole in the gasket to connect the power valve area to manifold vacuum. After I put the carb back on, I'll see if this really makes a significant difference:



Thank you,
Bob

 

[bubba22349]

Never use a sealer on carb gaskets! Dry Float setting for your carb is 29/32 inch. How much of a seal do you have around the edge of the adapter with that base gasket? It is the standard thin base gasket if the adapter has a nice flat surface should work if not a thicker one may help you seal better and as a side benefit insulates the carb from heat

 

[62Ranchero200]

Never use a sealer on carb gaskets! Dry Float setting for your carb is 29/32 inch. How much of a seal do you have around the edge of the adapter with that base gasket? It is the standard thin base gasket if the adapter has a nice flat surface should work if not a thicker one may help you seal better and as a side benefit insulates the carb from heat

As far as I can tell, the adapter surface is completely flat. The gasket that was supplied with the carb was a thin one, but for some reason the vendor supplied two of them. I used both of them in an attempt to improve the seal.

Can you explain what you mean by "dry float setting"?

Thank you,
Bob

 

[62Ranchero200]

Sorry for the bad link. i will try to locate the manual somewhere else for you. It was very helpful. The float level is very important and if it is too high it will indeed cause a rich mixture. It needs to be at a predetermined level so there is a proper amount of fuel in the emulsion tubes, air bleeds and idle and main passages and you just cant see these even with the top off the carb.

Looks like you have a couple problems here. You said by introducing a vacuum leak it improved the idle, and by closing the choke plate it also improved. This is possible because the carb is no longer in the idle circuit and you will need to get the idle speed down in order to set the mixture screws and make the thing idle at all. I know, it sounds backwards if you are at 1200 rpm, there is a good chance you are not even in the idle circuit at all and would explain why the engine failed to respond to your adjusting the idle mixture screws.

I would give this a try. At 3/8 inch of gap in the bowl I would say it is a bit high. Set the mixture screws to 1.5 turns out from lightly seated. Lower the float a bit and start the engine again. You can run it with the top off of the car, keep an extinguisher handy just in case. 8) Advance the timing to where it idles the smoothest, disregard any timing marks and do it by ear for the moment. Adjust the idle down as much as possible and if needed adjust the timing for best idle. When you are able to get the idle speed in an area that is definitely in the idle circuit, try adjusting the idle mixture screws, again listen for the smoothest idle and keep the screws very close to each other in the amount of turns.

When you obtain a reasonable idle speed you can reset the timing and fine tune the mixture again.

BTW, why did you change carbs in the first place? Did you had a fuel related problem on your old set up?

Did not get around the adjusting the float level today, but did the following:

Re-assembled with great care to avoid vacuum leaks, cleaning all gasket mating surfaces thoroughly and using two stacked carb gaskets. Also, re-assembled with enlarged vacuum hole for power valve as explained in earlier post on this thread. All this seemed to help, as the engine had the best idle yet, now able to idle indefinitely in park or neutral (although not yet in drive).

Also, when I swapped to the Autolite I had to move the PVC connection from the old carb spacer to manifold vacuum. Disconnected this to see if it improved idle - it didn't.

Finally, looking into the carb when the engine is idling, noticed small (1/8") droplets of gas dripping from the venturi boosters. I'm no carb expert, but I don't think there's supposed to be liquid gas in the bore, other than from the accelerator pump. Could this be caused by a too-high float level?

Tomorrow, will try lowering the float level a bit.

Thank you,
Bob

 

[First Fox]

Yes, the fuel dripping from the boosters is certainly a sign of a high float level. You have in my opinion one of the best carbs ever made there, so keep at it man, you'll get it.

 

[62Ranchero200]

Yes, the fuel dripping from the boosters is certainly a sign of a high float level. You have in my opinion one of the best carbs ever made there, so keep at it man, you'll get it.

I tried adjusting the float level, but the carb issues are not resolved.

First, a reality check, bending the float down (increasing the angle between the float and its attached extension that operates the needle valve) should LOWER the bowl level, right?

I bent the float down - once installed the float only had about 3/16" of an inch travel at the float end (away from the extension). The engine idled slightly better, idling in gear for maybe 30 seconds before dying. 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.

At this point, I see two issues: regardless of the float setting, the bowl still overflows and then the engine dies (flooded or overrich mixture). Also, even when the bowl isn't overflowing, gas droplets are dripping from one venturi booster. I think this is what is making the engine idlle so badly.

I'm just about stumped ... thinking I'm going to have to take the car to a carburetor shop, something I shouldn't have to do after buying a rebuilt carb.

Thank you,
Bob

 

[First Fox]

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.