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1960 lincoln continental carb issues (again0.


BryanFJ1

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Hi everyone! It's been a while.

So, i don't really understand why does this car always having troubles with the carburetor...

Like, last time it was a stuck needle.. Before that it was something else...

AND NOW - it's something new.

So last couple of months i started noticing that the mixture is off by the the smell of the exhaust.

Then i started noticing that the car is getting really rough idle...

And then i noticed it's exhaust is getting smoky and like i have to keep the car running on a pretty high idle and yet it's always trying to stall if i am not pressing gas pedal.

So i finally decide to take the top cover off -  and there was SATINS of the gasoline and gas was present at the top of the carb. 

I marked where it was coming from with the stains... (See screenshot)

image.png.12f1a7ec9ad3de87fb3e1fb2ca056b97.png

Like, when the car is about to stall - you could see gas there - you press the gas pedal and it's going away...

 

So at this point i am thinking that there is two little idle thrusters in the middle of it (Right on top of the mixture screws), that are somehow got blocked/gummed.

Twisting and turning the mixture screws didn't do anything no mater how i tried.

So, here we go... Taking the whole thing apart. Again....

 

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The guy on Motor Trend TV Roadworthy Restorations usually puts a carb kit in and then when that doesn’t work as well as he hoped he just happens to have a new in the box aftermarket carb to replace the original and all is good.
 

Sounds like you’ve been down this path before.  Good luck!

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Your float needle is not holding. Possibilities are that the float has a leak or if a composite one it has become waterlogged. (Is that the word, or gaslogged). what about fuel pressure. If you  dont have the stock pump your pressure may be too high. Just a start.

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My brother has a 65 Lincoln, with a similar AFB carb and his needle valves gave the same issue. His used neoprene tipped needles, and I have heard that these give problems when used with fuel containing "ethanol" which I believe is mandated over in your part of the world. Might pay to check it out. Other than that his old AFB has been a very good carb.

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I'm not sure you fix anything long by getting rid of the neoprene though. The earlier kind with all metal needles just barely worked when new.

 

Either way, if the carb is getting too full either the needle and seat is bad, or the float is bad, or the fuel pressure is too high.

 

Edited by Bloo (see edit history)
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As mentioned by others, the fuel level in the bowl is too high.

 

WHY???

 

(1) Non-stock fuel pump or modern "replacement stock" fuel pump with excessive fuel pressure

(2) Defective float (originals were brass and could be tested in hot water)

(3) Float level not correct

 

The neoprene fuel valves don't give near as much trouble as the earlier monel steel versions did; would doubt this is the problem. The folks that have a shiny new aftermarket carb in the box FOR SALE can always find some excuse to sell one and relieve the customer of more money.

 

If the fuel level in the bowl is too high, adjusting the mixture screws will have very little to no effect.

 

Suggestion: BEFORE disassembly of the carburetor, test the fuel pressure.

 

Jon

Edited by carbking (see edit history)
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I had to leave the computer for an early appointment before finishing the above post.

 

From the articles section of my website:

 

 

"Conventional pointed valve with brass seat

 

This valve is the valve of choice for virtually all original applications. There are a number of variations of the valve: monel steel tipped solid valve, monel steel tipped valve with spring and plunger, neoprene tipped solid valve, neoprene tipped valve with spring and plunger, plastic solid valve, and brass or monel steel solid valve, with neoprene washer encapsulated in the seat.

One may find lots of posts on various internet forums concerning the neoprene tip. Many have had issues with the neoprene tipped valves, and immediately determine (erroneously) that the neoprene tipped valve is not compatible with the current blends of fuel. Our testing has not found this to be an issue. However, many NEWER neoprene tipped fuel valves do fail prematurely. It is our opinion the reason for this premature failure is due to the valve manufacturers eliminating the “staking” procedure from the manufacture of the fuel valve seat to allow the valves to be sold cheaper. Staking was simply driving a hardened pointed tool against the broached orifice of the seat. This procedure would eliminate any sharp edges created with the broaching procedure, and create a chamfer that would give the valve a greater seating area. The sharp edges can cut into the neoprene tip, thus causing premature failure. The enthusiast can approximate this procedure prior to installing the new fuel valve in the carburetor. To do so, the enthusiast should assemble a block of wood, a steel ball approximately 1 ½ times the diameter of the seat orifice, a steel drift punch, and a ball peen hammer. Place the threaded end of the seat on the wood block (this prevents thread damage), place the ball inside the seat where the valve would normally fit, place the drift punch on top of the ball, and strike the drift punch with the hammer. CAUTION – use the ball only once.

The spring-loaded valves were developed in the 1930’s (I think by Carter) for use on carburetors designed for off-road or marine applications. The spring minimizes the movement of the float during severe service, and maintains a more constant fuel level in the bowl.

Carter tried a thermoplastic valve back in the 1930’s, as the alcohol being used (yes Virginia, ethanol has been tried and rejected several times as a fuel; each generation has to prove to itself the problems of ethanol) would corrode the monel steel valves. The thermoplastic was impervious to the ethanol, but the point of the valve wore prematurely.

Carter also tried a solid valve made from either brass or monel steel that pressed against a neoprene washer encapsulated in the seat. These valves didn’t last long in production, but I do not know why."

 

Ethanol gets lots of negative press (and deserves most of it ;) ) but this is not one of the ethanol issues. In fact, while we still will supply steel valves for die-hard old-timers (an old-timer is someone older than me ;) ) at extra cost; the steel valves will have more issues than the neoprene valves as the ethanol will eventually cause the steel to rust!

 

Unfortunately, the design of some older carburetor fuel valves is such that they cannot be replaced with neoprene valves at a reasonable expense, so we are forced to use steel for these valves.

 

If the OP truly believes the internet gossip concerning the neoprene valves, we can supply a rebuilding kit for the Lincoln AFB with the steel valves BUT I WOULD ADVISE AGAINST IT!

 

EDIT: Steel valves and ethanol

 

Jon

Edited by carbking (see edit history)
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One final? comment or food for thought:

 

Our shop truck (Ford) has TWO modified Lincoln AFB carbs similar to the one pictured by the OP.

 

These have neoprene fuel valves.

 

I have no local supply for non-ethanol fuel.

 

Because of summer temperatures and the volatility of modern fuel, I installed a Carter ELECTRIC fuel pump that produces approximately 7.5 psi (I DO NOT RECOMMEND THIS PRESSURE TO MOST). Carter used at least 5 different floats of varying buoyancy and several different fuel valve orifices in the AFB carbs. When modifying the Lincoln carbs, I installed the largest (highest buoyancy) floats, and a medium orifice fuel valve (I knew what my requirements would be).

 

Because I do not know what is in the OP's carb, my 7.5 psi is probably 2~2.5 psi too much; but if the carb was rebuilt by someone with a medium understanding of carbs and a desire to do a good job, it should hold 5 psi without issues.

 

Oh, and the reliability???

 

The two carbs on our shop truck were TROUBLE-FREE FOR 19 YEARS until I decided the old truck needed air conditioning. The truck sat in the air conditioning shop for 2 years while the owner assembled all of the necessary parts (the truck could have been ordered with A/C) and the carbs gummed up and needed rebuilding after the truck exited the shop.

 

Jon

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Posted (edited)
17 hours ago, Oldtech said:

If you  dont have the stock pump

It's a aftermarket mechanical pump with the orifice fuel filter after it with the line back to the tank (To make the gasoline running and cooling the pump)

image.png.fe677cd545c9538bcea1776c821803b9.png

14 hours ago, Bloo said:

or the fuel pressure is too high.

There miiiight be that the line back to the tank got clogged, but i doubt it. Gasoline that is being sucked from the tank is getting filtered twice. But you never know...

And yet - even if the line back to the tank is clogged - mechanical pump has a feature to stop pumping gas when there is already enough gas in the car.

3 hours ago, carbking said:

if the carb was rebuilt by someone with a medium understanding of carbs

Well.. that's was me a year ago or soo ^^'... Even though i wasn't tearing everything apart, it's just car was sitting for too long and the gas levels dropped to the point where there was such an angle - the float stuck needle pretty brutal. Like when i got the top of the carb out, i tried to press it with my finger to "unstuck" it like gas would do. It was stuck dead lol. Even have a picture from that time...

image.png.89bd0e73793914380b857d5e10ec5aa3.png

 

Also i have a question - why do you need to test the float in the hot water and not just a regular water if it floats or not? 

Is it something related to the brass? 

 

 

Good thing i have two carbs right now. I can you second one just for part's for the main one.. (Plus i have some parts from the rebuilt kit)

image.png.d17cc6392e3ae0ab17b8f4233cd03a16.png

 

 

Edited by BryanFJ1 (see edit history)
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There is air inside the float.

 

Hot water will pressurize the air and the inside of the float, and any hole will blow a stream of bubbles like an intertube with a hole. And you completely submerge the float for several seconds.

 

Water that is cooler than the ambient temperature will cause a partial vacuum inside the float, and will probably not show leaks. In fact, it MIGHT actually draw water into the float. You can check an intertube in cold water because the intertube is pressurized. With the float, you are depending on the heat to provide the pressure.

 

If the vapor line is installed correctly, and dumps into the top of the fuel tank, the pressure is "probably" OK, but I like testing, not "probably". Have you checked the pressure right at the carburetor inlet?

 

Jon

Edited by carbking (see edit history)
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18 hours ago, carbking said:

Have you checked the pressure right at the carburetor inlet?

 No, not yet. And i don't really know how tbh..

Is there a special tool for that? 

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1 hour ago, BryanFJ1 said:

 No, not yet. And i don't really know how tbh..

Is there a special tool for that? 

You might need to make a “T” connection for this with the leg of the T suppling gas to a pressure gauge.  The older vacuum gauges have a fuel pump pressure reading option built in to them and probably show how to do this using the hoses and fittings that come with it, assuming you have the instructions.

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You generally have to come up with your own fittings for carbureted cars. I have a kit for fuel injection that has about 100 pieces of brass in it, but the gauge range is all wrong for carburetors. Usually with the vacuum/pressure gauge (the one with an appropriate range for carburetors) they just give you a rubber hose and you are on your own. Back in the day, I made a tee by taking a K-car 3-port fuel filter and drilling out the orifice in the third port. On cars with an inline filter connected with hoses, I just substitute my filter for the existing one (paying attention to get the direction correct) and i'm in. I don't think you can even buy a K-car fuel filter anymore. On cars that have no rubber hoses connecting a filter, you usually had to buy or scrounge some fittings to get in.

 

The gauge is rather hard to read. It is going to kick all over the place until the float valve closes, and then you will have a very short time to read it before it starts kicking again. If you know that you should be able to get a reading, unless the float valve is not sealing which may very well be the case here. If so, it will never stop kicking.

 

If that doesn't give you any meaningful results, try deadheading the fuel pump into the gauge (no carburetor) and crank (or you could start it if there's some gas in the carb). It should rise right to max and stay there, and then you can get a reading, although the reading you get might be as much as half a pound or so(?) higher than reality.

 

It shouldn't leak down very fast after you stop cranking if the valves in the fuel pump are any good. That, however is a separate issue.

 

Edited by Bloo (see edit history)
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3 hours ago, Bloo said:

If that doesn't give you any meaningful results, try deadheading the fuel pump into the gauge (no carburetor) and crank (or you could start it if there's some gas in the carb). It should rise right to max and stay there, and then you can get a reading, although the reading you get might be as much as half a pound or so(?) higher than reality.

This idea was on my mind originally. The thing is - all the pressure is going to be dropping because of the fuel line back to the tank.

So the reading must be very very low, almost at 0 i believe...

 

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What do you mean? Does it have a return line? What you want for that test is the output of the fuel pump, no return line.

 

The two things that determine fuel pressure are the coil spring behind the diaphragm (not the spring you can see from outside the pump), and how far the diaphragm gets pushed up. If it is deadheaded, the diaphragm just stays up. The reading you get this way is maybe slightly(?) higher than reality because the pressure varies a little normally because the engine is normally burning fuel, and the float valve is leaking a little in to replace it, and the diaphragm isn't all the way up all the time. With it deadheaded, the pressure is at the maximum. If this pressure is in spec, or at worst only a tiny bit too high, I would call it normal and move on to the floats and float valves.

 

This test was done so rarely back in the day I am struggling to remember the details. But, it's 2024 now and mechanical fuel pumps with the wrong diaphragm spring and too much pressure are popping up everywhere. Just ask someone who has a Corvair....

 

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Well.. this is embarrassing...

So apparently last time i was "fixing" the stuck needle - i put the float wrong against the little bar that holds it.

So when the floats were up the the ceiling, it was simply not enough pressure to close the port holes with the needle...

 

Ugh, it took me, actually, twice to take the darn thing apart and to notice that.

Well. Now car is works like it should at least =___= 

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