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1984 Bronco, 4.9L, C6, 9", 44 TTB, 3.54 Gears
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Discussion Starter · #1 ·
My Bronco hasn't ran exceptionally well since I removed the TFI ignition and did the Duraspark II swap. The Duraspark is great. The carburetor has been garbage.

So, I ordered up a new rebuilt carburetor from Mike's Carburetors. It's a YFA Carter. I put it on, and the Bronco fired right up, idled well, but it was running SUPER rich, and flooding out the shop with fumes.

I've been messing with this carb for three days straight. It ran good for all of ten minutes yesterday. When I went back out to the shop to fine tune the idle and such, it started running rich again as soon as I started it up.

There is gas blowing out of the top of the intake, and the whole bottom side of the intake has blackened the block. I'm assuming this issue is causing problems with the fuel/air mixture, and is the root of all problems.

In researching replacing the gaskets, I've found a lot of people suggesting Mr. Gasket 260. However, after reading more, it looks like I'll need to separate the intake and exhaust in order to bolt them back on. My exhaust intake has already been welded once, and I doubt the bolts connecting the two together are going to come out very nicely.

I'm really thinking about just leaving this Bronco sit until I can buy a 4160 390 CFM Holley, Offenhauser C intake, and headers from Clifford Performance. This is what I want to go to, but it'd be nice to have the damn thing running so I can move it in and out of the shop easily.

Can anybody confirm that the gaskets leaking are the issue of the rich mixture? I've turned the fuel/air the whole way in (not over tightening it, stopping when it's fully seated), and it's still RICH.

Also, I let my Bronco run for a long while when the thing was running, and it never overheated, so from my other thread about the cooling I highly doubt I have any head gasket issues. It's hovering right at 190 degrees. The oil dipstick had rust on it, too. So I'm assuming this truck had sat in Texas for a long time without being ran.
 

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1984 Bronco, 4.9L, C6, 9", 44 TTB, 3.54 Gears
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Discussion Starter · #4 ·
To summarize my rant, I have gas and smoke coming from my intake manifold. I believe it's causing my carb issues, and wanted a confirmation.

I'm just going to replace both the intake and the exhaust manifolds with new parts, and a Remflex gasket from Bronco Graveyard. I'm currently trying to figure out if I want a 1980-1983 with no heat riser, or just get the 1984+ with the heat riser on the exhaust manifold. I really don't think my current set up has the heat riser. This thing has been hacked up...the current exhaust manifold is actually welded in a couple spots.
 

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Have you contacted Mike's Carburetors about the issue? It shouldn't be running that rich.
It's possible the accelerator pump diaphragm inside the carburetor isn't seated, or has a tear, etc. It is much like having a blown power valve on a Holley, and no matter what you do will lean it out because fuel is leaking past where it should be leaking. Things happen.

Nothing about the intake/exhaust would cause the carburetor to run rich, only the carburetor can do that.

Leaks in the intake would cause it to run lean, since it would be sucking in unnecessary air.

However, that said, the "combustion manifold" (the term for an intake and exhaust manifold that's bolted together as one unit) that the 300 has does have a habit of warping over the years. It generally requires being taken to a machine shop and having it planed flat before installing a new gasket.

There is also a gasket that goes between the intake and exhaust manifolds. It's possible that it's blown out. If it is, you'll see a lot of "smoke" / exhaust in the engine bay coming from that area. It won't affect how the engine runs all that much though.

I'd still look at the carburetor.
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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If you can turn the idle mix screw all the way in without killing the engine, you have a vacuum leak. A leaking intake manifold is a huge vacuum leak. At least on a holley...

For the intake and exhaust manifold gasket, there are only two good choices: Remflex or Flatout brands. And there isnt a need to separate the two manifolds if you use an engine hoist to move them around... Haha them bitches are heavy.

My 300 came to me with a 390 holley atop a clifford intake and headers. Ran great for a 300. Power to 5000 rpms. Ive since upgraded the cam, compression, valves, etc and its now fed by a 450 quickfuel carb (holley 4160).

AB popped in as i was typing this up. He knows his carbs! Ive never messed with a Carter YF(A)
 

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1984 Bronco, 4.9L, C6, 9", 44 TTB, 3.54 Gears
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Discussion Starter · #7 · (Edited)
Have you contacted Mike's Carburetors about the issue? It shouldn't be running that rich.
It's possible the accelerator pump diaphragm inside the carburetor isn't seated, or has a tear, etc. It is much like having a blown power valve on a Holley, and no matter what you do will lean it out because fuel is leaking past where it should be leaking. Things happen.

Nothing about the intake/exhaust would cause the carburetor to run rich, only the carburetor can do that.

Leaks in the intake would cause it to run lean, since it would be sucking in unnecessary air.

However, that said, the "combustion manifold" (the term for an intake and exhaust manifold that's bolted together as one unit) that the 300 has does have a habit of warping over the years. It generally requires being taken to a machine shop and having it planed flat before installing a new gasket.

There is also a gasket that goes between the intake and exhaust manifolds. It's possible that it's blown out. If it is, you'll see a lot of "smoke" / exhaust in the engine bay coming from that area. It won't affect how the engine runs all that much though.

I'd still look at the carburetor.
I did contact Mike's Carburetors and they asked what I installed it on, and said there's really no adjustments for the carb. I sent them an e-mail this morning before work, so I'll see what they say. All I know is that, while the old Ebay carb ran pretty terribly, it didn't run this rich. As soon as I put that carburetor on from Mike's the whole shop filled with smoke that smelled like straight gas.

Pretty sure I'm still going to replace both the manifolds, all gaskets, and run it like this for awhile before dropping the coin on a 4BBL set up. As of right now, I'm remodeling my shop and REALLY need to be able to start it and back it out of the shop! So, I'm really frustrated at the moment.

If you can turn the idle mix screw all the way in without killing the engine, you have a vacuum leak. A leaking intake manifold is a huge vacuum leak. At least on a holley...

For the intake and exhaust manifold gasket, there are only two good choices: Remflex or Flatout brands. And there isnt a need to separate the two manifolds if you use an engine hoist to move them around... Haha them bitches are heavy.

My 300 came to me with a 390 holley atop a clifford intake and headers. Ran great for a 300. Power to 5000 rpms. Ive since upgraded the cam, compression, valves, etc and its now fed by a 450 quickfuel carb (holley 4160).

AB popped in as i was typing this up. He knows his carbs! Ive never messed with a Carter YF(A)
I know I flooded the hell out of that last night in my frustration. Many choice words were used, and there was gas around the carb gasket. So...that didn't help anything. However, it did allow me to see the leaks around the intake gaskets.

No crane, so it'd be a nightmare trying to handle those bolted together without one. I can get all new everything for $400. What I don't want to do is tear this all apart to replace the gasket, just to find that they're both cracked.

EDIT: If it wasn't 10pm, the Bronco half way out of the garage, and me needing to get up at 4:30am the next day...it would've been a slightly more logical process. My shop doors have a 3" drop, so I pulled the Bronco by the front bumper by hand into the shop last night. Was almost certain the old ticker was going to explode...
 

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I remember the only time I've ever messed with that setup was without a hoist. I just leaned over and lifted it out. I also didn't have a step up or anything, so I think I was standing on the tire.
I got it out, but I think I was laid up for a few days as my back was pretty jacked. It's a huge chunk of cast iron. Fortunately, I was in my 20s, so rebounded pretty quickly.

Cleaning it up would make it run a lot nicer for sure, but again should still run with intake leaks. It might hesitate while accelerating, or die when you let off the gas, etc. Annoying things like that, but it's not going to dump fuel and run rich from it. Manifold leaks and excess fuel don't go together.

Maybe the float is sticking? Or maybe some dirt/junk in the needle/seat? Those would cause it to flood for sure.

One of the perks of the YF carb is that you can unscrew and remove the top of it without removing the carb from the intake. Just undo the bolts around the top, disconnect the idle cam arm, and carefully pull the top off. Spray out the needle/seat with some carb cleaner, and remove the accelerator pump from down inside and double check the diaphragm for tears.
 
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Discussion Starter · #9 ·
I remember the only time I've ever messed with that setup was without a hoist. I just leaned over and lifted it out. I also didn't have a step up or anything, so I think I was standing on the tire.
I got it out, but I think I was laid up for a few days as my back was pretty jacked. It's a huge chunk of cast iron. Fortunately, I was in my 20s, so rebounded pretty quickly.

Cleaning it up would make it run a lot nicer for sure, but again should still run with intake leaks. It might hesitate while accelerating, or die when you let off the gas, etc. Annoying things like that, but it's not going to dump fuel and run rich from it. Manifold leaks and excess fuel don't go together.

Maybe the float is sticking? Or maybe some dirt/junk in the needle/seat? Those would cause it to flood for sure.

One of the perks of the YF carb is that you can unscrew and remove the top of it without removing the carb from the intake. Just undo the bolts around the top, disconnect the idle cam arm, and carefully pull the top off. Spray out the needle/seat with some carb cleaner, and remove the accelerator pump from down inside and double check the diaphragm for tears.
So, I found something on Mike’s website explaining that the fuel/air adjustment will only make a difference at a low idle.

Today I bought a vacuum gauge, because the Bronco doesn’t have a tach. The intake gasket and the welded hole smoked like crazy until it ran long enough to get hot.

The idle now is perfect, and I also fine tuned the timing. The Bronco was idling at a steady 20 on the vacuum gauge.

Unfortunately flooding it killed my oil change I just did with VR1 Racing oil, and I burned through a 1/4 tank of ethanol free 91. Haha!

Intakes need replaced and then it should be running well, very well.
 

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Discussion Starter · #10 ·
Any recommendations on decent intakes for the 300 and 1BBL carb?
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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There is only factory manifolds available now for single barrel carbs. The mainfold set weighs probably 100 lbs. Edelbrock used to make a single bbl manifold but they are rare. I think @SRWillis had one.

When needing to move a vehicle, try to grab and roll a tire. I can move mine around by myself in this way, and im a soaking wet 170 lbs. Of course the larger the tire and bigger lugs help.
 

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1984 Bronco, 4.9L, C6, 9", 44 TTB, 3.54 Gears
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Discussion Starter · #12 ·
There is only factory manifolds available now for single barrel carbs. The mainfold set weighs probably 100 lbs. Edelbrock used to make a single bbl manifold but they are rare. I think @SRWillis had one.

When needing to move a vehicle, try to grab and roll a tire. I can move mine around by myself in this way, and im a soaking wet 170 lbs. Of course the larger the tire and bigger lugs help.

100lbs? This is going to suck.

Can you hang the exhaust manifold on studs, and then sit the intake down on top, or does it all have to go in together?
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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100lbs? This is going to suck.

Can you hang the exhaust manifold on studs, and then sit the intake down on top, or does it all have to go in together?
You can hang the exhaust. Better yet is to hang it and bolt the collector up. It does not have to go in or come out as a single piece.

I did check, i have a single grungy carter YFA on the shelf, as well as a 74 exhaust manifold. And a pair of efi exhaust manifolds and an efi lower intake.

Have you checked out FordSix.com? They know sixes inside and out.
 

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1984 Bronco, 4.9L, C6, 9", 44 TTB, 3.54 Gears
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Discussion Starter · #14 ·
You can hang the exhaust. Better yet is to hang it and bolt the collector up. It does not have to go in or come out as a single piece.

I did check, i have a single grungy carter YFA on the shelf, as well as a 74 exhaust manifold. And a pair of efi exhaust manifolds and an efi lower intake.

Have you checked out FordSix.com? They know sixes inside and out.
When I use my Google-fu for inline 6 questions, it usually takes me to that site. However, finding a recommendation on the best factory replacement intake is tough. Most people put on a 4BBL.
 

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95 5.8L MAF XLT, Hedman Shorties/MF SS Y & Muff, E4OD, Man hubs, KYB Quads, 31x10.5x15, 304K miles
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Here is some interesting info on what you are looking at doing to your engine! It is very Technically detailed in following the theories/rules of Fluid dynamics (Air Flow Science). It explains WHY "bigger isn't always better"! There is a lot to learn here and it explains it very well.


Here are the Dyno results that show some of what was talked about in the above Article, all from the same Source!


This last one takes the above Testing to another level!

 

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1981 Bronco, 4.9L, ZF5, NP208, Detroit Truetracs, 3.55 gears, 31" Wranglers front and rear
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Any recommendations on decent intakes for the 300 and 1BBL carb?
There is only factory manifolds available now for single barrel carbs. The mainfold set weighs probably 100 lbs. Edelbrock used to make a single bbl manifold but they are rare. I think @SRWillis had one.
I did have a 1V Edelbrock intake (sold it), but they are rare and therefore more $$ than a new 4V Offy manifold. I don't know if it was much better than stock or not; I remember a couple people on here commenting it probably wasn't. It did have a cool factor though.

I went with an Offy C with a Quick Fuel 450 and am well satisfied.

...a pair of efi exhaust manifolds and an efi lower intake.
I would suggest going with these, they're what I'm running. They are supposed to be nearly as good as headers w/o the hassles. I'm sure @BigBlue 94 will take good care of you. Then you can go to Rock Auto (or elsewhere) and buy the exhaust to bolt to them.
 
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Discussion Starter · #17 ·
I don’t want to put the EFI intake on. Just want to find a decent quality factory replacement.

Tired of researching modifications, honestly.
 

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82 XLT Lariat 351w, Edelbrock 1406 4bbl ,C6 auto, auto locking hubs ,33x10.5x15
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burned through a 1/4 tank of ethanol free 91. Haha!
Might be unrelated but my 82 hated that high grade ethanol free gas. She ran really rich and got worse mileage then me running regular 87 with ethanol neutralizer.
 

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Discussion Starter · #19 ·
It runs great now. Serious intake leaks make it run like garbage.
 

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1981 Bronco, 4.9L, ZF5, NP208, Detroit Truetracs, 3.55 gears, 31" Wranglers front and rear
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