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170 Carter BBS issues?
https://www.slantsix.org/forum/viewtopic.php?t=56373		 Page 2 of 2
Author:  matv91 [ Wed Oct 15, 2014 7:23 pm ]
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In this link http://www.carburetorfactory.com/expvw02.html That 31 Retainer-float pin. Make sure that's there and working. Long time ago i had a BBS that flooded a lot. That retainer was gone.
Author:  Eatkinson [ Fri Oct 17, 2014 12:58 am ]
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Did the suggested mods and tested tomight. Fuel is still boiling into the Venturi and puddling on the manifold floor causing rough restarts.

What else do I need to check? Could something be clogged that i need to clear out?
Author:  wjajr [ Fri Oct 17, 2014 6:54 am ]
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Grasping at straws department:

Realize without eyes and hands on this fuel dribble dilemma it is hard to see what's going on with all possible peripheral off spec contributions to the problem.

Two things come to mind that may or may not be applicable: perhaps there is a small leak between fuel pump and fuel bowl's needle valve allowing pressure drop in fuel line after shut down which lowers fuel's resistance to boiling; or needle valve/ float seal is defective allowing expansion of fuel from excess heat to over fill fuel bowl after shut down.

Something ain't right with that carburetor, because most of our slants tolerate normal overdriving temperatures after shut down with no fuel blow-by dribbling into manifold.

One more thought in the running hot camp:
Using a laser thermometer, get some temperature readings at idle at each cylinder's exhaust port where exhaust manifold mates with head and report back findings. It could be as simple as excessive retarded timing dumping too much heat into exhaust system causing overheating of the intake components.
Author:  Eatkinson [ Fri Oct 17, 2014 10:02 am ]
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I'd love to replace this one-year only Carter BBS with a like-kind new one. Anyone got a spare for me?

:roll:

Thinking about this logically, the engine is no longer running hot - it's normal temp now, and the fuel is now being protected from excess heat with the mod.

Just last night, I also lowered the float valve in the bowl from 7/32 to 5/16 (approx) to account for greater fuel expansion (2014 ethanol blended fuel) vs. pure gas. I don't have a proper gauge for measuring this - was using a mic, but seemed approximately correct.

There is NO needle/seat valve in this setup. I'm using the Daytona float valve - a redesigned valve that's designed to seat correctly under all circumstances, where the needle/seat valve is prone to failure. Yet this cannot be the problem: I was experiencing this issue before I rebuilt the carburetor, when I had the original needle/seat valve in place. No, something else is up.

I'm double-checking and verifying that the exhaust manifold heat riser valve is fully in the open position and not flapping around when warm. Seemed fine when I checked yesterday, but I'm going to check again. As people have said, a closed valve would lead to heat build-up in the carb throat. That seems to be happening. Trying to source the heat that's making the fuel boil over.

When the float valve shuts fuel off from entering the bowl after engine shut-down, are there any points or passages within the carburetor that if blocked, would cause fuel to boil over into the throat? I am noticing that the area around the accelerator plunger vent gets a bit wet from fuel, which shouldn't really be happening....?
Author:  SlantSixDan [ Fri Oct 17, 2014 12:11 pm ]
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Quote:
I'd love to replace this one-year only Carter BBS with a like-kind new one.
That'll be a very long search. You'd be way far ahead to look at newer-than-'60 carbs that will fit perfectly and have a whole lot of design fixes compared to the '60 unit.

Quote:
I also lowered the float valve in the bowl from 7/32 to 5/16 (approx) to account for greater fuel expansion (2014 ethanol blended fuel) vs. pure gas.
There is no greater expansion of today's fuel vs. yesterday's. What's working against you right now is volatility.
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I don't have a proper gauge for measuring this - was using a mic, but seemed approximately correct.
You need to use the correct tool for the job. Given that there's a perceptible difference in engine operation caused by a float setting 1/16" higher or lower, "approximately correct" doesn't really help you much.
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There is NO needle/seat valve in this setup. I'm using the Daytona float valve
It's still correct to call it an inlet needle/seat.
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I'm double-checking and verifying that the exhaust manifold heat riser valve is fully in the open position and not flapping around when warm.
Are you sure the actual flapper (inside the exhaust manifold) is present and correctly clocked on the shaft? They can eventually fail/break off or even spin on the shaft.
Quote:
a closed valve would lead to heat build-up in the carb throat.
This valve doesn't really open or close. It shifts between heat-on and heat-off. Neither is an open or a closed position. And it's not heat buildup in the carb throat that's making problems, it's heat buildup in the carb bowl.
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When the float valve shuts fuel off from entering the bowl after engine shut-down, are there any points or passages within the carburetor that if blocked, would cause fuel to boil over into the throat?
No, but are you sure your bowl vent (the little round disc that rides on the accelerator pump stem) is being lifted to the correct height when the carb is at curb (hot) idle position?
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I am noticing that the area around the accelerator plunger vent gets a bit wet from fuel, which shouldn't really be happening....?
Pretty normal, but if it's more than "a bit" wet, the fuel level is likely too high.
Author:  Eatkinson [ Fri Oct 17, 2014 9:37 pm ]
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Quote:
That'll be a very long search. You'd be way far ahead to look at newer-than-'60 carbs that will fit perfectly and have a whole lot of design fixes compared to the '60 unit.
Ok. What model carb do you suggest as the best fit for what I have to work with?
Quote:
You need to use the correct tool for the job. Given that there's a perceptible difference in engine operation caused by a float setting 1/16" higher or lower, "approximately correct" doesn't really help you much.
Can you suggest a brand/model of float gauge? I'm finding a bunch of motorcycle float gauges but nothing that looks remotely close to the gauge pictured in the FSM. Nor am I locating a float gauge that is of a different and more modern/adjustable design, where I can tell right away that it would work.
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Are you sure the actual flapper (inside the exhaust manifold) is present and correctly clocked on the shaft? They can eventually fail/break off or even spin on the shaft.
Yes the flapper is present and rotates back and forth easily. In use terms, this exhaust manifold is on the newer side. No, I'm not in the habit of second-guessing whether they clocked it correctly on the shaft, and I'd have to tear the system apart again in order to check this. I won't be doing that unless absolutely necessary and I can't figure this out by checking other aspects of the system first.
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This valve doesn't really open or close. It shifts between heat-on and heat-off. Neither is an open or a closed position. And it's not heat buildup in the carb throat that's making problems, it's heat buildup in the carb bowl.
Noted. Good point.
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No, but are you sure your bowl vent (the little round disc that rides on the accelerator pump stem) is being lifted to the correct height when the carb is at curb (hot) idle position?
I have not checked this yet with the drill bit as a measurement. I've got the hairpin clip on the shaft in the middle position as the FSM instructed.
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Pretty normal, but if it's more than "a bit" wet, the fuel level is likely too high.
I am still wondering about this. No point in doing anything until I get my hands on the right float gauge.
Author:  SlantSixDan [ Fri Oct 17, 2014 10:31 pm ]
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Ok. What model carb do you suggest as the best fit for what I have to work with?
Check yr email. Image
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Can you suggest a brand/model of float gauge?
No such. They used to come with carb kits, but now all you get (if you get anything) is a useless strip of paper. I have some NOS carb kits with real float gauges in them.
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Quote:
are you sure your bowl vent (the little round disc that rides on the accelerator pump stem) is being lifted to the correct height when the carb is at curb (hot) idle position?
I have not checked this yet with the drill bit as a measurement. I've got the hairpin clip on the shaft in the middle position as the FSM instructed.
OK to eyeball this, you're looking for at least 1/8" between the disc and the carb top with the throttle at curb (hot) idle position. Try raising the clip to the upper slot and see if that helps alleviate the condition.
Author:  Eatkinson [ Sat Oct 18, 2014 12:06 am ]
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Quote:
Check yr email.
Nothing yet.
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I have some NOS carb kits with real float gauges in them.
I'll get one of these from you for the gauge, if you have one to spare.
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OK to eyeball this, you're looking for at least 1/8" between the disc and the carb top with the throttle at curb (hot) idle position. Try raising the clip to the upper slot and see if that helps alleviate the condition.
Will do.
Author:  matv91 [ Sat Oct 18, 2014 12:03 pm ]
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Found old post ,on this. http://www.slantsix.org/forum/viewtopic.php?t=8345
Author:  SlantSixDan [ Sat Oct 18, 2014 12:56 pm ]
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Quote:
Quote:
I have some NOS carb kits with real float gauges in them.
I'll get one of these from you for the gauge, if you have one to spare.
I do. In fact, those kits are taking up space I need back, and I'm not using them, so I need to clear a bunch of them out. I've got kits for BBS, BBD, 1920, probably others. All good-quality kits, too, not junk; if you buy one of the old Tomco kits you may find out where Daytona Parts got the idea for their "new" Daytona Float Valve. :shock:

I'll try and get 'em catalogued and listed in an ad on here. Might do a high-resolution precision scan of the gauges before sendout.
Author:  Reed [ Sat Oct 18, 2014 2:42 pm ]
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FYI- if anyone is interested, I MIGHT have access (through my brother's girlfriend's place of employment) to a computerized CNC mill that could reproduce in METAL, not paper or cardboard, the float setting gauges.
Author:  SlantSixDan [ Sat Oct 18, 2014 3:26 pm ]
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Well, I can probably supply the patterns...!
Author:  curmudgeon [ Sun Oct 19, 2014 9:43 am ]
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FYI- if anyone is interested, I MIGHT have access (through my brother's girlfriend's place of employment) to a computerized CNC mill that could reproduce in METAL, not paper or cardboard, the float setting gauges

I would be very interested in purchasing such a gauge(s).
Author:  Reed [ Sun Oct 19, 2014 10:00 am ]
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If enough interest manifests, I will approach my potential source and see what it would cost to do a run of the gauges.
Author:  Eatkinson [ Sun Oct 19, 2014 2:37 pm ]
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Well count me in!
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