Engine Will it fit/work

manicmechanic007 · Jul 11, 2022

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

7991LXnSHO · Jul 11, 2022

manicmechanic007 said:
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
Year	Power	Torque	Induction	Transmission	Note

1983	175 hp (130 kW) @ 4200 rpm	245 lb⋅ft (332 N⋅m) @ 2400 rpm	4V carb	SROD or T-5
1984	165 hp (123 kW) @ 3800 rpm	245 lb⋅ft (332 N⋅m) @ 2000 rpm	EFI (CFI)	AOD
	205 hp (153 kW) @ 4200 rpm	267 lb⋅ft (362 N⋅m) @ 2400 rpm	4V carb	T-5
1985	165 hp (123 kW) @ 3800 rpm	245 lb⋅ft (332 N⋅m) @ 2000 rpm	EFI (CFI)	AOD	through 11/19/84
	180 hp (134 kW) @ 3800 rpm	245 lb⋅ft (332 N⋅m) @ 2000 rpm	EFI (CFI)	AOD	after 11/19/84
	210 hp (157 kW) @ 4400 rpm	265 lb⋅ft (359 N⋅m) @ 3200 rpm	4V carb	T-5
1986	200 hp (149 kW) @ 4000 rpm	285 lb⋅ft (386 N⋅m) @ 3000 rpm	SEFI	AOD or T-5

limp · Jul 11, 2022

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 · Jul 11, 2022

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 · Jul 11, 2022

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

FoxChasis · Jul 11, 2022

manicmechanic007 said:
Mustang GT's never got CFI like the Lincolns and T Birds

12% of 1984 Mustang GT hatchbacks had AOD and CFI
33% of 1984 Mustang GT convertibles had AOD and CFI

14% of 1985 Mustang GT hatchbacks had AOD and CFI
40% of 1985 Mustang GT convertibles had AOD and CFI

Randy1985 · Jul 12, 2022

7991LXnSHO said:
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 · Jul 12, 2022

Randy1985 said:
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 · Jul 12, 2022

Randy1985 said:
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.

Mustang5L5 · Jul 12, 2022

7991LXnSHO said:
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

Vs CFI

Spot the difference

General karthief · Jul 12, 2022

I do.

7991LXnSHO · Jul 12, 2022

Mustang5L5 said:
The CFI and 4V carb engine bay layouts are pretty similar

Carb

Vs CFI

Spot the difference

Thanks! I was going to look for pics like these. I even see three letters.

Randy1985 · Jul 12, 2022

Mustang5L5 said:
The CFI and 4V carb engine bay layouts are pretty similar

Carb

Vs CFI

Spot the difference

This is exactly what it looks like. So my car was efi? Most likely

7991LXnSHO · Jul 12, 2022

Randy1985 said:
This is exactly what it looks like. So my car was efi? Most likely

One lid says EFI, the other does not. Although the lid could have been switched or the letters worn off.
Also, what transmission do you have? That’s harder to change than the lid.

Randy1985 · Jul 12, 2022

7991LXnSHO said:
One lid says EFI, the other does not. Although the lid could have been switched or the letters worn off.
Also, what transmission do you have? That’s harder to change than the lid.

Manual T5

7991LXnSHO · Jul 13, 2022

Randy1985 said:
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.

Holley Sniper 550-870 Stealth 4150 EFI, Shiny

The Sniper Stealth 4150 EFI system from Holley features 4,100LB/HR Fuel Injectors capable of supporting up to 650 HP naturally aspirated or 600 HP on forced induction applications. The Sniper Stealth 4150 ECU is capable of fuel map self-learning and ignition timing control, improving idle...

www.speedwaymotors.com

Mustang5L5 · Jul 13, 2022

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"

manicmechanic007 · Jul 13, 2022

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 · Jul 13, 2022

Randy1985 said:
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 said:
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 · Jul 13, 2022

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.

Street Demon 1901 625 CFM 4 Barrel Carburetor, Polymer Main Body

WICKED POWER! The ALL NEW Street Demon™ redefines the street carburetor with clean looks and ease of use! The Street Demon offers enthusiasts a straightforward four barrel carburetor designed to deliver a stable idle, amazingly crisp throttle response and smooth performance. Its optimized...

www.speedwaymotors.com

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

https://www.summitracing.com/parts/dem-sda-650-ms?seid=srese2&utm_source=bing&utm_medium=cpc&utm_campaign=Brands+%7C+D&utm_term=4581390076848049&utm_content=GSAPI+5b9ad3f8eb511

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.

Engine Will it fit/work

manicmechanic007

7991LXnSHO

wanna catch the space herp

limp

wrap a little cheese around it and its a done

manicmechanic007

Mustang5L5

That is…until I whipped out my Bissell

FoxChasis

Randy1985

Member

7991LXnSHO

wanna catch the space herp

7991LXnSHO

wanna catch the space herp

Mustang5L5

That is…until I whipped out my Bissell

General karthief

wonder how much it would cost to ship you a pair

7991LXnSHO

wanna catch the space herp

Randy1985

Member

7991LXnSHO

wanna catch the space herp

Randy1985

Member

7991LXnSHO

wanna catch the space herp

Holley Sniper 550-870 Stealth 4150 EFI, Shiny

Mustang5L5

That is…until I whipped out my Bissell

manicmechanic007

LILCBRA

I wish I didn't have all of these balls in the air

7991LXnSHO

wanna catch the space herp

Street Demon 1901 625 CFM 4 Barrel Carburetor, Polymer Main Body

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