Ignition Troubleshooting

[mat in tn]

I agree the choke should not have changed and the 4 bbl guys will have to help if that's where it is. You're in FL so I don't know what the difference in temps are for summer to wnter - some guys have to make a slight adjustment. Might make a difference? Slight?

Is it possible on your carb to disable the entire secondary circuit in some way?

As for rebuilding carbs, it isn't a really big deal. You want everything super clean - all the passages need to flow freely and any moving parts need to move freely. Floats need to float and move freely and the passages need to flow correctly. All that comes from everything being super clean. And maybe new parts if there is excessive wear or floats aren't floating.

BUt anyone with a little know how should be fine on a first time rebuild. Be organized and clean. And try to lay it all out on a bench where you can work from start to finish without disturbing the porject where you might lose parts. Get some sort of organizing device, muffin pan, storage box with little dividers, etc. to keep track of parts. Take photos as you go of where everything is. tape labels if you need them.

You may want a bucket of parts cleaner to dip things in over night if it's terrible. be careful what you dip - some parts don't get dipping in carb cleaner. But since it runs, it may just need some spray cleaner. When I used to do motorcycle carbs, I used torch tip cleaners, wire strands, whatever to clean passages. Plus some compressed air or carb cleaner squirted through. Every passage goes somewhere.

Pay attention to gaskets and parts as you dismantle it and make sure you have NEW parts that are identical.

Clean it all, replace parts, do float adjustments as needed. Reassemble. Pray a little maybe. What can it hurt, right?

Haha, you got that right. I'm in Central Florida, so temperature isn't a big factor, but she definitely performs better the warmer she is. I may start by replacing the rear fuel bowl float first and then move on to the rebuild attempt if that doesn't help.

before getting too far into the carb, let's be certain of a couple basics. if something changed its possible to be inside the carb but more likely not. I would start by making sure that there are no vacuum leaks. the most likely examples would be deteriorated hoses, cracked hoses where they fit onto any components or cracked vacuum caps. missing even. loose carb mounting nuts is also a possibility although more common on the l6 models. identify all vacuum ports on either the intake manifold or carburetor. cap them all with new vinyl caps (the pretty colored ones) they do not dry rot and crack like rubber. mark all hoses that you remove so you can put them back exactly. then start and tune the engine. if it runs better then add one hose at a time until you have all done paying attention if it runs poorly again.

I say this because at idle you should not be able to change much by messing with the rear float level other than idle quality. and the fact that you can says that the needle and seat seem to be working as is the float. you should be setting the float with the sight screw removed and the fuel level just trickling at the bottom of the screw hole. engine running. you set the front the same way.

[Bullnose Gator]

before getting too far into the carb, let's be certain of a couple basics. if something changed its possible to be inside the carb but more likely not. I would start by making sure that there are no vacuum leaks. the most likely examples would be deteriorated hoses, cracked hoses where they fit onto any components or cracked vacuum caps. missing even. loose carb mounting nuts is also a possibility although more common on the l6 models. identify all vacuum ports on either the intake manifold or carburetor. cap them all with new vinyl caps (the pretty colored ones) they do not dry rot and crack like rubber. mark all hoses that you remove so you can put them back exactly. then start and tune the engine. if it runs better then add one hose at a time until you have all done paying attention if it runs poorly again.

I say this because at idle you should not be able to change much by messing with the rear float level other than idle quality. and the fact that you can says that the needle and seat seem to be working as is the float. you should be setting the float with the sight screw removed and the fuel level just trickling at the bottom of the screw hole. engine running. you set the front the same way.

I will certainly have more questions about the vacuum trouble shooting, but just to share more info about the rear bowl I'll share that when I adjust it to where the sight plug shows the fuel at just barely spilling out (a gentle rocking of the truck makes it lap out a trickle) it will idle ok for only a matter of a minute or so before stalling out. When I adjust it back all the way down to where even a hard rock of the truck makes no fuel come out of the sight plug is when it runs its best. the front bowl is at the perfect level and I stopped adjusting it weeks ago because it doesn't seem to be causing any change in performance.

[mat in tn]

I will certainly have more questions about the vacuum trouble shooting, but just to share more info about the rear bowl I'll share that when I adjust it to where the sight plug shows the fuel at just barely spilling out (a gentle rocking of the truck makes it lap out a trickle) it will idle ok for only a matter of a minute or so before stalling out. When I adjust it back all the way down to where even a hard rock of the truck makes no fuel come out of the sight plug is when it runs its best. the front bowl is at the perfect level and I stopped adjusting it weeks ago because it doesn't seem to be causing any change in performance.

this may seem odd. however. when you have it running, with the float level set, and it starts to run poorly after running for a moment. is that with the sight screw still out? if so, hold a finger closing it off while its running for a moment and see if the run quality changes. if it changes move your finger and see if it floods out. that will tell you the state of your needle and seat/float.

[FuzzFace2]

this may seem odd. however. when you have it running, with the float level set, and it starts to run poorly after running for a moment. is that with the sight screw still out? if so, hold a finger closing it off while its running for a moment and see if the run quality changes. if it changes move your finger and see if it floods out. that will tell you the state of your needle and seat/float.

I would say also look down in the carb on the rear to see if fuel is dripping in.

No power valve in the rear so that cant be it.

I wonder if a gasket is causing fuel to leak when the level is up to the normal place?

I am guessing the carb uses a metering plate and not a block with jets as most Holley's do.

Wonder if the plate could be warped?

They are not hard to rebuild and if you follow what was posted you should be fine on the rebuild.

Dave ----

[Bullnose Gator]

this may seem odd. however. when you have it running, with the float level set, and it starts to run poorly after running for a moment. is that with the sight screw still out? if so, hold a finger closing it off while its running for a moment and see if the run quality changes. if it changes move your finger and see if it floods out. that will tell you the state of your needle and seat/float.

I would say also look down in the carb on the rear to see if fuel is dripping in.

No power valve in the rear so that cant be it.

I wonder if a gasket is causing fuel to leak when the level is up to the normal place?

I am guessing the carb uses a metering plate and not a block with jets as most Holley's do.

Wonder if the plate could be warped?

They are not hard to rebuild and if you follow what was posted you should be fine on the rebuild.

Dave ----

So I ran it with the needle/seat raised to where fuel was just trickling out of the sight plug. As it was running a little rough I plugged the sight plug and it barely started running a little rougher. When I removed my finger fuel poured out. I didn't notice any fuel in the rear barrels. Also, the choke stays in the 100% open position whether it's idling or revved. How should the choke be positioned during a normal/healthy idle?

[mat in tn]

So I ran it with the needle/seat raised to where fuel was just trickling out of the sight plug. As it was running a little rough I plugged the sight plug and it barely started running a little rougher. When I removed my finger fuel poured out. I didn't notice any fuel in the rear barrels. Also, the choke stays in the 100% open position whether it's idling or revved. How should the choke be positioned during a normal/healthy idle?

once warmed up the choke should be wide open, and the fast idle cam released. revving the engine should have no effect on choke position. other than releasing the choke on the first rev. if it was able to stack fuel to the point of flooding out when you removed your finger then the needle and seat are not shutting off the incoming fuel completely. that will be from too much fuel pressure or bad needle/seat of bad float. you were already looking in those areas and that should have proven that you are on the right track. when you remove the float, if it is brass shake it to see if there is any fuel sloshing around inside. if there is its trash. get another one. however changing the needle and seat is simple and done in place without disassembly of the carb so I would start there.