Nothing Special's '71 Bronco

[grumpin]

OK, that's annoying, but I'll take it. It's running fine now.

Backing up a bit...

I decided to test a few things. I do have a fuel pressure gauge, but i haven't been looking at it that much as I've been trying things. So I thought I'd check the fuel pressure at a high idle (2000 - 3000 rpm) and then see what it was under load at the same engine speed. Maybe not an iron-clad diagnostic, but it seemed likely that if there was a fuel delivery issue it may well show up as lower fuel pressure under load.

Second was still looking for a vacuum leak. As I said before, it's a pretty simple vacuum system. But the one thing that seemed most suspect was easiest to check. So I pulled off the hose to the PCV valve and capped the port.

The third thing was getting back to fuel delivery. I was thinking that the issue must be related to the work I did over the winter. But the carb wasn't the onlt part of the fuel system I worked on. I also replaced the fuel tank switch valve. What if the holes through that are too small?

So for starters I pulled the PCV hose and went for a drive to look at the fuel pressure gauge. I figured I'd leave bypassing the switching valve for another drive. But on this drive everything worked great! No bogging under heavier throttle, even with the choke all the way in! The fuel pressure gauge was rock-steady at 4.25 psi no matter what the load (it did drop a bit as the engine speed went below about 1500 rpm).

So it must be the PCV, right? Wrong. I hooked the PCV back up and it's still running great.

The only thing I thought of after I had parked it and Lesley and I were on a walk was that over the winter the main tank was full of fuel and the aux tank was empty. I was running on the main, but on my last test drive before today I filled the aux tank, and near the end of that drive I switched to the fresh gas. It was still acting up a bit at the end of that drive, but it wasn't long enough for much of a test.

So maybe it's just bad gas? That's my best guess at this point. I did turn the low speed screws in another turn, so they're now at 1.5 turns out, which seems more normal. I'll drive the Bronco to work tomorrow and see if it stays good. Then later I'll probably switch back to the main tank and see if it starts to hiccup again.

So it's a little annoying when a problem just goes away and you don't know if it's going to come back. But for now I'll take that it's running well. And if I can turn the problem back on by switching to the main tank I'll be a lot happier.

Bittersweet, it’s running good but why?

Hope it goes well tomorrow.

[Gary Lewis]

Bittersweet, it’s running good but why?

Hope it goes well tomorrow.

I hadn’t thought of the gas. But that could do it. Hope you’ve found it!

[Nothing Special]

I hadn’t thought of the gas. But that could do it. Hope you’ve found it!

Well I made it in to work. Generally it ran pretty well, but it did run better with the choke pulled out slightly.

I'm wondering if I just need to go up a size or two in the main jets? I'm running the jets that came with this junkyard carb and they've always seemed OK. But I've never done anything to make sure they're RIGHT.

The jets for this Autolite 2100 look a lot like the jets I used to have for my Holley 4150. Doe anyone know if they are interchangeable? I haven't started looking for Autolite jets yet, but generally Holley stuff is a lot easier to find.

[Nothing Special]

Well I made it in to work. Generally it ran pretty well, but it did run better with the choke pulled out slightly.

I'm wondering if I just need to go up a size or two in the main jets? I'm running the jets that came with this junkyard carb and they've always seemed OK. But I've never done anything to make sure they're RIGHT.

The jets for this Autolite 2100 look a lot like the jets I used to have for my Holley 4150. Doe anyone know if they are interchangeable? I haven't started looking for Autolite jets yet, but generally Holley stuff is a lot easier to find.

I found out they're not interchangeable, on my carb anyway. Apparently Holley jets have a 1/4" thread OD. Early Autolites (up to about 1963) used 1/4", but then they switched to 5/16", which is what mine measure. And so far I'm striking out trying to find Autolite / Motorcraft jets

[FuzzFace2]

I found out they're not interchangeable, on my carb anyway. Apparently Holley jets have a 1/4" thread OD. Early Autolites (up to about 1963) used 1/4", but then they switched to 5/16", which is what mine measure. And so far I'm striking out trying to find Autolite / Motorcraft jets

And why I went with a Holley 2300 carb on my AMC 304 motor.

Yes the AMC used a Motorcraft carb and the Holley was a direct bolt on, even took the factory AMC air filter assy.

Dave ----

[Nothing Special]

And why I went with a Holley 2300 carb on my AMC 304 motor.

Yes the AMC used a Motorcraft carb and the Holley was a direct bolt on, even took the factory AMC air filter assy.

Dave ----

I did find some on-line. Hopefully they will be here soon.

I have thought about getting a new carb, But I had a Holley 4150 on my CJ5. After a bunch of work it was pretty good off-road. But my Autolite is better. Way less issues at steep angles or hitting big rocks. I just can't see going to anything that will be worse at that. So EFI is a possibility. But I like the cost advantage of my existing carb. And I kind of like the bragging rights when someone with EFI sees my Bronco make a steep climb and asks "is that thing still carbureted?"

[FuzzFace2]

I did find some on-line. Hopefully they will be here soon.

I have thought about getting a new carb, But I had a Holley 4150 on my CJ5. After a bunch of work it was pretty good off-road. But my Autolite is better. Way less issues at steep angles or hitting big rocks. I just can't see going to anything that will be worse at that. So EFI is a possibility. But I like the cost advantage of my existing carb. And I kind of like the bragging rights when someone with EFI sees my Bronco make a steep climb and asks "is that thing still carbureted?"

I found on Holley's running the fuel level a little lower helped a little but they also make a off road float kit.

It is a spring loaded float to keep it from bouncing.

We also ran a rubber hose from vent tube to vent tube and cut a little V notch in the top center.

This would keep fuel that may come up the vent tube from going down the carb it would go to the rear float bowl.

There is also vent extensions that fit on the inside of the bowl that also help keep fuel from coming up the vents. This is used mostly in the front bowl on drag cars as the fuel would rush to the back of the bowl, up the vent tube and flood the motor. It would cut out slow down and no more fuel down the carb and race was lost. Because we did hill drags & climbs this was an issue with us racing off road.

Just FYI

Dave ----

[Nothing Special]

I found on Holley's running the fuel level a little lower helped a little but they also make a off road float kit.

It is a spring loaded float to keep it from bouncing.

We also ran a rubber hose from vent tube to vent tube and cut a little V notch in the top center.

This would keep fuel that may come up the vent tube from going down the carb it would go to the rear float bowl.

There is also vent extensions that fit on the inside of the bowl that also help keep fuel from coming up the vents. This is used mostly in the front bowl on drag cars as the fuel would rush to the back of the bowl, up the vent tube and flood the motor. It would cut out slow down and no more fuel down the carb and race was lost. Because we did hill drags & climbs this was an issue with us racing off road.

Just FYI

Dave ----

I did add the off-road floats to my Holley, as well as vent baffles. I don't recall if there was anything else, but those were the main things that made it almost as good as an Autolite.

Prior to making those mods I'd also lower the float level to get it to run better off-road. And that helped a lot. But then it didn't run well on the road so I'd have to raise the floats back up when I got off the trail.

What I will say in favor of the Holley is that it was super-easy to change the float level (way easier than changing it on the Autolite). The Holley didn't even require opening the carb, it was just loosening a lock nut, turning a screw and tightening the lock nut. Plus there was a plug in the bowl that you could pull to see when the level was correct. Compare this to the Autolite where you need to take the top off the carb with the engine running to check the level, and then shut it off and bend the float to adjust it, and then run it again to see if you made the right change. (I tried to check the float level wet last night and sprayed gas all over the place on top of the running engine. That method sucks!!!! )

Changing the power valve was also easier on the Holley. It required pulling the bowl which dumped a bunch of gas on the exhaust manifold of my in-line 6, but it didn't require removing the carb from the vehicle like the Autolite does.

I will give the Autolite the edge in changing jets. Pulling the bowl on the Holley dumps a bowl-full of gas, while taking the top off the Autolite doesn't spill any. But otherwise the Holley is definitely easier to adjust.

[FuzzFace2]

I did add the off-road floats to my Holley, as well as vent baffles. I don't recall if there was anything else, but those were the main things that made it almost as good as an Autolite.

Prior to making those mods I'd also lower the float level to get it to run better off-road. And that helped a lot. But then it didn't run well on the road so I'd have to raise the floats back up when I got off the trail.

What I will say in favor of the Holley is that it was super-easy to change the float level (way easier than changing it on the Autolite). The Holley didn't even require opening the carb, it was just loosening a lock nut, turning a screw and tightening the lock nut. Plus there was a plug in the bowl that you could pull to see when the level was correct. Compare this to the Autolite where you need to take the top off the carb with the engine running to check the level, and then shut it off and bend the float to adjust it, and then run it again to see if you made the right change. (I tried to check the float level wet last night and sprayed gas all over the place on top of the running engine. That method sucks!!!! )

Changing the power valve was also easier on the Holley. It required pulling the bowl which dumped a bunch of gas on the exhaust manifold of my in-line 6, but it didn't require removing the carb from the vehicle like the Autolite does.

I will give the Autolite the edge in changing jets. Pulling the bowl on the Holley dumps a bowl-full of gas, while taking the top off the Autolite doesn't spill any. But otherwise the Holley is definitely easier to adjust.

You didnt keep a spray paint can cap in the tool box?

You pull 1 of the lower bowl screws and catch the fuel in the cap.

You might need 2 caps now that I think of it, been a bit since I had to do this.

Dave ----

[Nothing Special]

You didnt keep a spray paint can cap in the tool box?

You pull 1 of the lower bowl screws and catch the fuel in the cap.

You might need 2 caps now that I think of it, been a bit since I had to do this.

Dave ----

Today I checked the float level wet, without spraying too much gas over the engine. The first time I tried (a few days ago) the fuel was pretty low in the bowl when I started the engine, so the needle valve was pretty far open. That gave a pretty impression of an arterial bleed with a geyser of fuel on each fuel pump stroke.

This time I dumped a little gas in the bowl to make sure the needle valve was closed when I started the engine. Once I saw fuel start squirting again I shut off the engine and measured the fuel level. With the needle valve not open very far it didn't geyser so bad, but it still didn't all stay in the bowl. Like I said before, that method of setting a float level sucks!

I don't have an official spec for the fuel level, for some reason the spec sheet that I have doesn't have that one listed. But I found a bulletin board thread that said it should be 7/8". And then I saw another thread that said it should be .8". So I don't know exactly what it should be, but after setting the dry level correctly at 7/16" the wet level is .81".

A lower number means a higher float level, so it seems like if anything my float is still a little high. But since my issues could possibly be caused by a low float and if anything my float is high, I'm thinking I'll leave it where it is.