The Ford Barn

Planojc · 09-13-2014, 06:55 PM

59AB with a 94 carb. Engine runs like a top at about 900 rpm’s and up, but at idle it runs rough, stumbles and pops. Looking down the throat of the carb. I can see gas dripping from the main nozzle on the driver side down on the throttle plate, thus causing the popping sound. I have checked the float level, float valve and can’t seem to solve the problem. Fuel pump pressure is at 2.5 lbs. Any ideas?

Ross F-1 · 09-13-2014, 08:19 PM

Power valve? Would seem to affect both sides tho.

dude · 09-13-2014, 09:26 PM

I agree, power valve.

supereal · 09-13-2014, 10:14 PM

Replacement power valves often have a radius where they screw into the carb bowl. If so, they need to be put in a lathe and turned flat so the gasket will seal. If you have ever had a backfire thru the carb, it is more than likely the diaphragm was damaged, allowing a leak into the manifold.

Planojc · 09-14-2014, 07:38 AM

I have replaced the 5.5 PV and I always fill the float bowl with gas and let sit to check for leaks around the taper. The problem is that for some reason gas seems to be pulled up from the idle tube at idle and causing a drip out the bottom of the main nozzle down on the throttle plate. It looks like it's doing this only on one side.

LOWRIDER · 09-14-2014, 07:46 AM

Sponsored Links (Register now to hide all advertisements)

Had the same problem on a 3x2 w/94's. I ended up setting the float levels lower than what the spec was.

jimvette59 · 09-14-2014, 08:37 AM

Is the float bowl vented. Is there a hole in the float bowl area. Just saying.

Charlie ny · 09-14-2014, 09:36 AM

Plano,
Not all PV's are created equal. If you can find the type with 4 small bleed holes around the shank you will find they are more trouble free than the window style.
I have these 4 hole style PV's with the correct gaskets. I machine the gasket face
as well.
Charlie ny
[email protected]

Planojc · 09-14-2014, 05:08 PM

I have tried three PV from working carbs. Problem still there.

Bruce Compton, Canada · 09-14-2014, 05:51 PM

Hi : I've rebuilt well over 100 of these carbs and it's extremely rare to find one that does not have warped mating surfaces, both between the air horn and the main body as well as between the main body and the cast iron throttle body. The upper one is not that critical, but the lower one sure is. The power valve requires vacuum to hold it closed, and when the mating surfaces surrounding the power valve are warped, an air (vacuum) leak will not allow enough vacuum build-up to close the valve. Take the carb apart , remove the gasket between these two parts, match them up, and hold them together lightly and you will see light between the surfaces. Most guys overtighten the three screws here and that's what starts the warping. Apparently 8 in. lbs. is the required torque on these three screws. Actually the whole problem originated with a poor design as there should have been at least five screws surrounding the power valve, not just three. I remember as a teenager trying kit after kit to get these things working right and never could do it until I finally took the time to figure out what was actually going on. The warped surfaces can be milled flat if you have a machinist buddy, or you can file them flat if you are really careful and take your time. In either case a proper cleaning will be necessary to remove any filings. Good luck : Bruce

flatjack9 · 09-14-2014, 08:34 PM

Have you tried lowering the float level slightly? It may be that one throat is slightly more sensitive to air flow than the other, hence causing only one side to leak.

41ford1 · 09-14-2014, 09:25 PM

Quote:

Originally Posted by Bruce Compton, Canada

Hi : I've rebuilt well over 100 of these carbs and it's extremely rare to find one that does not have warped mating surfaces, both between the air horn and the main body as well as between the main body and the cast iron throttle body. The upper one is not that critical, but the lower one sure is. The power valve requires vacuum to hold it closed, and when the mating surfaces surrounding the power valve are warped, an air (vacuum) leak will not allow enough vacuum build-up to close the valve. Take the carb apart , remove the gasket between these two parts, match them up, and hold them together lightly and you will see light between the surfaces. Most guys overtighten the three screws here and that's what starts the warping. Apparently 8 in. lbs. is the required torque on these three screws. Actually the whole problem originated with a poor design as there should have been at least five screws surrounding the power valve, not just three. I remember as a teenager trying kit after kit to get these things working right and never could do it until I finally took the time to figure out what was actually going on. The warped surfaces can be milled flat if you have a machinist buddy, or you can file them flat if you are really careful and take your time. In either case a proper cleaning will be necessary to remove any filings. Good luck : Bruce

Bingo!! The flatness and fit area is critical.

Mart · 09-15-2014, 03:29 AM

Good info coming out in this thread. Thanks Bruce, Charlie etc.

Mart.

Planojc · 09-15-2014, 08:27 AM

Thanks Bruce and Flatjacj. This is the kind of information I was looking for. I will check and report back.
John

Mart · 09-16-2014, 03:49 AM

I tore my twin 94's down and checked the flatness. they were both warped. I used abrasive paper on the table of my drilling machine and got them flat. havn't tried them yet, but thanks for the tip.

Mart.

Kurt in NJ · 09-16-2014, 07:10 AM

Another thing that can cause such problems --a twisted throttle shaft--one butterfly is more open than the other and it makes for problems at idle, but not noticed above idle

Charlie ny · 09-16-2014, 07:23 AM

Plano,
What Bruce said x 2. I find it mandatory to machine the bowl and base flat
to achieve a proper vac seal. Sometimes the problem you are having goes further.
If the nozzle bars are not flat on the gasket faces where they meet the bowl OR
if the gasket faces on the bowl are not right where the nozzle bars seat that
messes things up in a hurry. One step further is the power valve gasket seat on
the bowl. That seat is as cast and occasionally not square with the pv threads....
all the soft squishey gaskets in the world won't make that situation go away......
the pv gasket face in that case must be machined. I made a bluing gauge to check
this face....9 out 10 will be ok....you may have #10.
Charlie ny

Planojc · 09-16-2014, 07:31 AM

Looks like Bruce nailed it. Warped at the two screw tabs big time. Also there may be some leaking around the throttle shaft. When replacing the gaskets I found I have two different types of gaskets and some are much thicker than the others. Can't remember where I got the thick ones but would think that they would seal better.

09-13-2014, 08:19 PM	#2
Ross F-1 Senior Member Join Date: Nov 2010 Location: NM Posts: 2,438	Re: Carberator woes, Help Power valve? Would seem to affect both sides tho. __________________ '52 F-1, EAB flathead

09-13-2014, 09:26 PM	#3
dude Senior Member Join Date: May 2010 Location: Kansas Posts: 334	Re: Carberator woes, Help I agree, power valve. __________________ [QUO[/QUOTE]no matter where you are,or where you're at, there you are...

09-13-2014, 10:14 PM	#4
supereal Senior Member Join Date: Jul 2014 Location: Iowa Posts: 1,634	Re: Carberator woes, Help Replacement power valves often have a radius where they screw into the carb bowl. If so, they need to be put in a lathe and turned flat so the gasket will seal. If you have ever had a backfire thru the carb, it is more than likely the diaphragm was damaged, allowing a leak into the manifold.

09-14-2014, 07:38 AM	#5
Planojc Senior Member Join Date: May 2010 Location: Plano, Texas Posts: 843	Re: Carberator woes, Help I have replaced the 5.5 PV and I always fill the float bowl with gas and let sit to check for leaks around the taper. The problem is that for some reason gas seems to be pulled up from the idle tube at idle and causing a drip out the bottom of the main nozzle down on the throttle plate. It looks like it's doing this only on one side.

09-14-2014, 07:46 AM	#6
LOWRIDER Senior Member Join Date: May 2010 Location: Kingman Az. 86409 Posts: 419	Re: Carberator woes, Help Sponsored Links (Register now to hide all advertisements) Had the same problem on a 3x2 w/94's. I ended up setting the float levels lower than what the spec was. __________________ Dan Kingman Az. 86409

09-13-2014, 06:55 PM	#1
Planojc Senior Member Join Date: May 2010 Location: Plano, Texas Posts: 843	Carberator woes, Help 59AB with a 94 carb. Engine runs like a top at about 900 rpm’s and up, but at idle it runs rough, stumbles and pops. Looking down the throat of the carb. I can see gas dripping from the main nozzle on the driver side down on the throttle plate, thus causing the popping sound. I have checked the float level, float valve and can’t seem to solve the problem. Fuel pump pressure is at 2.5 lbs. Any ideas?

09-14-2014, 08:37 AM	#7
jimvette59 Senior Member Join Date: Jun 2010 Location: Perry OH Posts: 1,330	Re: Carberator woes, Help Is the float bowl vented. Is there a hole in the float bowl area. Just saying.

09-14-2014, 09:36 AM	#8
Charlie ny BANNED Join Date: May 2010 Posts: 3,019	Re: Carberator woes, Help Plano, Not all PV's are created equal. If you can find the type with 4 small bleed holes around the shank you will find they are more trouble free than the window style. I have these 4 hole style PV's with the correct gaskets. I machine the gasket face as well. Charlie ny [email protected]

09-14-2014, 05:08 PM	#9
Planojc Senior Member Join Date: May 2010 Location: Plano, Texas Posts: 843	Re: Carberator woes, Help I have tried three PV from working carbs. Problem still there.

09-14-2014, 05:51 PM	#10
Bruce Compton, Canada Senior Member Join Date: May 2010 Posts: 416	Re: Carberator woes, Help Hi : I've rebuilt well over 100 of these carbs and it's extremely rare to find one that does not have warped mating surfaces, both between the air horn and the main body as well as between the main body and the cast iron throttle body. The upper one is not that critical, but the lower one sure is. The power valve requires vacuum to hold it closed, and when the mating surfaces surrounding the power valve are warped, an air (vacuum) leak will not allow enough vacuum build-up to close the valve. Take the carb apart , remove the gasket between these two parts, match them up, and hold them together lightly and you will see light between the surfaces. Most guys overtighten the three screws here and that's what starts the warping. Apparently 8 in. lbs. is the required torque on these three screws. Actually the whole problem originated with a poor design as there should have been at least five screws surrounding the power valve, not just three. I remember as a teenager trying kit after kit to get these things working right and never could do it until I finally took the time to figure out what was actually going on. The warped surfaces can be milled flat if you have a machinist buddy, or you can file them flat if you are really careful and take your time. In either case a proper cleaning will be necessary to remove any filings. Good luck : Bruce

09-14-2014, 08:34 PM	#11
flatjack9 Senior Member Join Date: May 2010 Location: Oshkosh, Wi Posts: 4,526	Re: Carberator woes, Help Have you tried lowering the float level slightly? It may be that one throat is slightly more sensitive to air flow than the other, hence causing only one side to leak.

09-15-2014, 03:29 AM	#13
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,749	Re: Carberator woes, Help Good info coming out in this thread. Thanks Bruce, Charlie etc. Mart.

09-15-2014, 08:27 AM	#14
Planojc Senior Member Join Date: May 2010 Location: Plano, Texas Posts: 843	Re: Carberator woes, Help Thanks Bruce and Flatjacj. This is the kind of information I was looking for. I will check and report back. John

09-16-2014, 03:49 AM	#15
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 8,749	Re: Carberator woes, Help I tore my twin 94's down and checked the flatness. they were both warped. I used abrasive paper on the table of my drilling machine and got them flat. havn't tried them yet, but thanks for the tip. Mart.

09-16-2014, 07:10 AM	#16
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,158	Re: Carberator woes, Help Another thing that can cause such problems --a twisted throttle shaft--one butterfly is more open than the other and it makes for problems at idle, but not noticed above idle

09-16-2014, 07:23 AM	#17
Charlie ny BANNED Join Date: May 2010 Posts: 3,019	Re: Carberator woes, Help Plano, What Bruce said x 2. I find it mandatory to machine the bowl and base flat to achieve a proper vac seal. Sometimes the problem you are having goes further. If the nozzle bars are not flat on the gasket faces where they meet the bowl OR if the gasket faces on the bowl are not right where the nozzle bars seat that messes things up in a hurry. One step further is the power valve gasket seat on the bowl. That seat is as cast and occasionally not square with the pv threads.... all the soft squishey gaskets in the world won't make that situation go away...... the pv gasket face in that case must be machined. I made a bluing gauge to check this face....9 out 10 will be ok....you may have #10. Charlie ny

09-16-2014, 07:31 AM	#18
Planojc Senior Member Join Date: May 2010 Location: Plano, Texas Posts: 843	Re: Carberator woes, Help Looks like Bruce nailed it. Warped at the two screw tabs big time. Also there may be some leaking around the throttle shaft. When replacing the gaskets I found I have two different types of gaskets and some are much thicker than the others. Can't remember where I got the thick ones but would think that they would seal better.