Engine Will it fit/work

manicmechanic007

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Sep 26, 2017
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Mustang GT's never got CFI like the Lincolns and T Birds
His 85 had a Holley 600 on it from the factory
The Mustangs went from the HO Holleys straight to multiport fuel injection in 86 or 87
Randy 1985, I think you should find a close to factory Holley 600 with the rear screws
Install it with some steel needles
Stock they run a bit faster than the fuelies
Stock they are worth more money
 
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7991LXnSHO

wanna catch the space herp
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Mustang GT's never got CFI like the Lincolns and T Birds
The previous (autocorrect!) information on CFI in automatic transmission cars and carbs with manual transmission cars was correct.
Mustang High Output (H.O.) 5.0L horsepower ratings by year
YearPowerTorqueInductionTransmissionNote
1983175 hp (130 kW) @ 4200 rpm245 lb⋅ft (332 N⋅m) @ 2400 rpm4V carbSROD or T-5
1984165 hp (123 kW) @ 3800 rpm245 lb⋅ft (332 N⋅m) @ 2000 rpmEFI (CFI)AOD
205 hp (153 kW) @ 4200 rpm267 lb⋅ft (362 N⋅m) @ 2400 rpm4V carbT-5
1985165 hp (123 kW) @ 3800 rpm245 lb⋅ft (332 N⋅m) @ 2000 rpmEFI (CFI)AODthrough 11/19/84
180 hp (134 kW) @ 3800 rpm245 lb⋅ft (332 N⋅m) @ 2000 rpmEFI (CFI)AODafter 11/19/84
210 hp (157 kW) @ 4400 rpm265 lb⋅ft (359 N⋅m) @ 3200 rpm4V carbT-5
1986200 hp (149 kW) @ 4000 rpm285 lb⋅ft (386 N⋅m) @ 3000 rpmSEFIAOD or T-5
 
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limp

wrap a little cheese around it and its a done
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The EX and I almost bought a White 85 GT 5 speed convertible brand new.... One of the big reasons was it being the last year for Carbs instead of the new fangled fuel injection voodoo stuff........... LOL
 

manicmechanic007

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I had no idea
We used to joke about Texas and Florida
Those markets they would experiment with
First V6 F150's were released in TX. The same for the Ecostar (the electric rooster)
I do not remember seeing a GT with CFI
All the cop cars we worked on had 5 speeds
 

Mustang5L5

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Just the autos had them but they looked like the carb cars


You can see the two fuel injectors in the “bowl”. With the air cleaner on youd never know although the air cleaner lid does say “5 Liter EFI HO” on it

FA5A59FE-3BB8-4BA1-83F2-1FD983EEBBA7.jpeg
 
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Randy1985

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So what do you mean by the response? Does it stumble when you tip in, when off the line, does it bog at full throttle? Is there a certain RPM it runs poorly at?
Does it not answer your questions politely or ignore you? (That last one is more likely from a black Pontiac named KITT or a computer named HAL, but I had to ask.)
Well the hit at take it’s stumbles and then picks back up. I thought fuel but installed new pump changed all filters and had carb rebuilt new pressure reg. And new plugs and wires still stumbling. The reason I ask about the vin code is because on each side in engine bay going into the fender well is to black air ducts like it was fuel injected
 

7991LXnSHO

wanna catch the space herp
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Well the hit at take it’s stumbles and then picks back up. I thought fuel but installed new pump changed all filters and had carb rebuilt new pressure reg. And new plugs and wires still stumbling. The reason I ask about the vin code is because on each side in engine bay going into the fender well is to black air ducts like it was fuel injected
It stumbles at take off? We can help that.
1. Accelerator pump - is/are it/they working and is/are it/they adjusted right? I am picturing it having accelerator pump cams that can be changed for a different shot like Holley’s.
2. Is the Street Demon a vacuum or double pumper mechanical secondary carb? (I could look and guess at the model, but will give you info for both.)
The vacuum secondary carb will have one accelerator pump on the driver’s front side, and a vac canister thing higher up on the passenger side toward the rear to control the secondaries. This is generally better for street driving, and is also better for mileage and generally for heavier cars.
The style that opens the secondaries mechanically needs two accelerator pumps. That’s the Double in double pumper. Light cars and racing are the most common use for these, but they can be tuned for street use, too.

Also, do you know what CFM the carb is? Anything bigger than a 600 or a 650 CFM will be overkill. A stick 302 at 6500 RPM only Needs 483 CFM.
 

7991LXnSHO

wanna catch the space herp
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The reason I ask about the vin code is because on each side in engine bay going into the fender well is to black air ducts like it was fuel injected
The GT’s had a dual snorkel round air cleaner that had accordions that went to a circle opening in each fender. (I added this to a ‘79 5.0.) I do not think it is an indication of CFI or not.
Does you car have a manual transmission or automatic? If it was a stock manual, carbed from the factory it was.
 
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Mustang5L5

Put lubricant all over the balls
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The GT’s had a dual snorkel round air cleaner that had accordions that went to a circle opening in each fender. (I added this to a ‘79 5.0.) I do not think it is an indication of CFI or not.
Does you car have a manual transmission or automatic? If it was a stock manual, carbed from the factory it was.

The CFI and 4V carb engine bay layouts are pretty similar

Carb
B555B727-DE64-407A-8A2A-F05F7A5889E3.jpeg


Vs CFI
EE31F89A-AD14-44F4-814D-E9B95B90EC81.jpeg




Spot the difference
 
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7991LXnSHO

wanna catch the space herp
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Manual T5
If that’s still not enough to convince you, pull the shifter boot and look at the hole in the transmission hump for the shifter. A hacked hole vs a factory cut will (almost always) be obvious.
So the idea of the early, factory CFI is not going to be budget or easy, and a newer system will run better.

I gave you some things to check in the carb. Now here is a link to a deal on the Holley Sniper EFI system. There are three pdf. manuals to read and see if you are up to the swap.
 
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Mustang5L5

Put lubricant all over the balls
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Is the door sticker still on the car?

Bottom right corner under “TR”. What letters/numbers are there.

You can also just pull the air cleaner lid and look for the two fuel injectors sitting in the "carb"

1657717321921.png
 
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manicmechanic007

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I Am I missing some more brain?
Where are the finned aluminum valve covers if that is a GT Mustang?
Might as well call it a throttle body to get him off on the right foot
Prefer stock but that cfi was a bit of a turd system
EEC III with the VV carb was way worse
Those injectors used to leak and drizzle
I replaced a bunch of them back when
That is all they ever needed
 

LILCBRA

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Well the hit at take it’s stumbles and then picks back up. I thought fuel but installed new pump changed all filters and had carb rebuilt new pressure reg. And new plugs and wires still stumbling. The reason I ask about the vin code is because on each side in engine bay going into the fender well is to black air ducts like it was fuel injected

It stumbles at take off? We can help that.
1. Accelerator pump - is/are it/they working and is/are it/they adjusted right? I am picturing it having accelerator pump cams that can be changed for a different shot like Holley’s.
2. Is the Street Demon a vacuum or double pumper mechanical secondary carb? (I could look and guess at the model, but will give you info for both.)
The vacuum secondary carb will have one accelerator pump on the driver’s front side, and a vac canister thing higher up on the passenger side toward the rear to control the secondaries. This is generally better for street driving, and is also better for mileage and generally for heavier cars.
The style that opens the secondaries mechanically needs two accelerator pumps. That’s the Double in double pumper. Light cars and racing are the most common use for these, but they can be tuned for street use, too.

Also, do you know what CFM the carb is? Anything bigger than a 600 or a 650 CFM will be overkill. A stick 302 at 6500 RPM only Needs 483 CFM.

Did you look at the video I shared on the first page? It goes over exactly what I think you're describing. It sounds like the accelerator pump as @7991LXnSHO is saying, the video addresses a couple of what seem to be common problems with the Street Demon carburetor.

I'm not horribly familiar with the Street Demon at all so I don't know anything about adjusting it. That would probably ring true for a lot of us as we've most likely only dealt with standard Holley or Edelbrock/Carter carbs. But it sounds like your accelerator pump isn't supplying enough fuel immediately when you step on the pedal. The shot needs to be supplied immediately as the throttle is opened, if it's not it'll stumble and fall on it's face. There's also a possibility that it isn't supplying enough fuel even if it's shooting fuel immediately. In that case you'd probably need to install a larger discharge nozzle.

To go along with the FI/carb debate, as I understood it they went with CFI on the auto only 5.0 in 84-5, then used the multiport in 86 for all. I do remember a big 'to-do' about the 85 cars being the last of the carbureted cars AND they were rated higher horsepower than the injected cars at the time, so a lot of people were turned off by that. Of course that started to change in 87, but fuel injection was still voodoo to a lot of people so a lot of cars had a carburetor swapped in.
 

7991LXnSHO

wanna catch the space herp
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Is this your carb? The accelerator pump is under the top cover. With an internal pump, there is usually a plunger or piston on the rod that’s connected to the linkage that goes through the top. If you are not getting a good squirt of fuel when pressing the throttle linkage, the pump cup is the first suspect.

I was picturing something more like this, but with a choke housing.

I think the first design was also a Holley patented design. With the fuel bowl gaskets above the fuel line, it’s less likely to have leaks. My traditional Holleys and Autolite carbs, (very similar), have not leaked due to dry bowl gaskets, but it has happened to some others I trust it not to have been user error.