Carb Swap Fuel Setup(help Needed)

Possessed94 · Dec 2, 2016

So I've carb swapped my car, and read the forums on how to setup the fuel system. This is my first time and want to make sure I do it right. Does anyone have pictures of their setup, an can give a vivid description on how to setup the fuel system on my car?
94 5.0 swapped w/carb

jozsefsz · Dec 2, 2016

We'd need a bit more information on what you plan to do and what you'd want to know. There are a lot of ways to get the fuel to the carb. For example, fuel-cell or stock tank? In-tank pump or external electrical? Or even mechanical pump?

I haven't run a carb swap on an injected car in 20 years (replacing a poorly functioning TBI back then) so I don't have pictures, primarily because I think it's a bit insane to remove an easily-tuneable computer and multi-port fuel injection from a car to put 100 year old expensive, inefficient, unreliable, and difficult to tune technology in its place. Bonus: you'll probably lose 20+ horses in the process and will curse the day you were born on cold mornings. Not to mention devaluing the car by wrecking it for emissions.

With that all said, the easiest way (imho) is to disconnect the stock pressure and return lines as they enter the engine bay and fab up some fittings. Run those lines to a fuel pressure regulator with output to the carb. Something like this (cheaper options are available too).
http://www.cjponyparts.com/holley-f...5/?year=1973&gclid=CPaHuq7X1tACFYKLswodJdoLqQ

Adjust pressure at the regulator to 5-6 psi. Replace the fuel pump circuit's EEC ground as it enters the CCRM with an ignition-switched relay. You're done.

90sickfox · Dec 2, 2016

Hey man.... I'm not going to dog you about going carbed. The most reliable mustang I ever had was carbed.

I met a kid today that didn't know what a distributor was....or that you could set timing by turning it...Smh Guess it would seem complicated to him ;shrug

On my last car, an 89, there was a restriction in my return line that kept pressure at 15psi using a return style FPR. That was too high so I ran a cheap restrictor style FPR from the regulator to the carb. If you drop the tank you can remove the old pump and run a piece of metal tube to just off the bottom of the tank. The return line can be capped off at the input to the old fuel pump assembly. You can then plumb an external low pressure pump after the fuel filter to a restrictor style FPR.

The pump should be powered on by a relay with battery power and a fuse.

If using the factory pump you'll have to run a separate power circuit and relay to turn pump on. I used an aeromotive return style regulator for a carb motor....and a Mr.gasket cheap restrictor regulator.

The distributor on your 95 will need to be changed to a carb style vacuum advance. Make sure the gear on it is for a roller cam or you can eat the gears up.

People will dog you for going carbed but I know a lot of carbed cars that are "dead nuts" reliable. The power isn't instant like EFI and, if street driven, its not as responsive.

I'm not carbed anymore and have gone completely in another direction.

My advise is to use a wideband o2 sensor to help tune the carb. I used an air fuel ratio gauge hooked to stock o2 sensor and I had an Edelbrock 650cfm carb. Adjusted idle screws and adjusted power valve.

When the temperature shifts expect to adjust the idle fuel ratio.

A lot of people get into trouble by trying to run a carb that's an incorrect size for their combo. The 650cfm was a little on the big side for a 306 with an e cam. A stock 302 will ( normally ) need around 500cfm.

When you are carbed the diag is simpler, if you understand the system. Tuning a carb can be a PITA but its nowhere near as hard as tuning my efi turbo 331.

The sensors involved in the efi system really do help efficiency. Adjustments for temperatures and atmospherical pressures happen automatically. You'll be losing that ability...so you'll have to ride a fine line- usually sacrificing some power and fuel efficiency in the process.

Possessed94 · Dec 2, 2016

jozsefsz said:
We'd need a bit more information on what you plan to do and what you'd want to know. There are a lot of ways to get the fuel to the carb. For example, fuel-cell or stock tank? In-tank pump or external electrical? Or even mechanical pump?

I haven't run a carb swap on an injected car in 20 years (replacing a poorly functioning TBI back then) so I don't have pictures, primarily because I think it's a bit insane to remove an easily-tuneable computer and multi-port fuel injection from a car to put 100 year old expensive, inefficient, unreliable, and difficult to tune technology in its place. Bonus: you'll probably lose 20+ horses in the process and will curse the day you were born on cold mornings. Not to mention devaluing the car by wrecking it for emissions.

With that all said, the easiest way (imho) is to disconnect the stock pressure and return lines as they enter the engine bay and fab up some fittings. Run those lines to a fuel pressure regulator with output to the carb. Something like this (cheaper options are available too).
http://www.cjponyparts.com/holley-f...5/?year=1973&gclid=CPaHuq7X1tACFYKLswodJdoLqQ

Adjust pressure at the regulator to 5-6 psi. Replace the fuel pump circuit's EEC ground as it enters the CCRM with an ignition-switched relay. You're done.

I understand that and appreciate the response. The car is intended for fun weekend cruises, no longer than a three-four hour drive; that's why I want to retain the stock fuel tank. Mainly being built as a street car, with some track play.

Possessed94 · Dec 2, 2016

90sickfox said:
Hey man.... I'm not going to dog you about going carbed. The most reliable mustang I ever had was carbed.

I met a kid today that didn't know what a distributor was....or that you could set timing by turning it...Smh Guess it would seem complicated to him ;shrug

On my last car, an 89, there was a restriction in my return line that kept pressure at 15psi using a return style FPR. That was too high so I ran a cheap restrictor style FPR from the regulator to the carb. If you drop the tank you can remove the old pump and run a piece of metal tube to just off the bottom of the tank. The return line can be capped off at the input to the old fuel pump assembly. You can then plumb an external low pressure pump after the fuel filter to a restrictor style FPR.

The pump should be powered on by a relay with battery power and a fuse.

If using the factory pump you'll have to run a separate power circuit and relay to turn pump on. I used an aeromotive return style regulator for a carb motor....and a Mr.gasket cheap restrictor regulator.

The distributor on your 95 will need to be changed to a carb style vacuum advance. Make sure the gear on it is for a roller cam or you can eat the gears up.

People will dog you for going carbed but I know a lot of carbed cars that are "dead nuts" reliable. The power isn't instant like EFI and, if street driven, its not as responsive.

I'm not carbed anymore and have gone completely in another direction.

My advise is to use a wideband o2 sensor to help tune the carb. I used an air fuel ratio gauge hooked to stock o2 sensor and I had an Edelbrock 650cfm carb. Adjusted idle screws and adjusted power valve.

When the temperature shifts expect to adjust the idle fuel ratio.

A lot of people get into trouble by trying to run a carb that's an incorrect size for their combo. The 650cfm was a little on the big side for a 306 with an e cam. A stock 302 will ( normally ) need around 500cfm.

When you are carbed the diag is simpler, if you understand the system. Tuning a carb can be a PITA but its nowhere near as hard as tuning my efi turbo 331.

The sensors involved in the efi system really do help efficiency. Adjustments for temperatures and atmospherical pressures happen automatically. You'll be losing that ability...so you'll have to ride a fine line- usually sacrificing some power and fuel efficiency in the process.

This car is intended to be my weekend warrior, hats why I chose carb. I'm not to much worried about gas mileage with it being the it won't be daily driven. I just want something easy to work on like you said, and that I can learn for my next build in the process.

CarMichael Angelo · Dec 4, 2016

Sigh,.......

You cannot run the stock fuel tank if it is your intent to also run the stock injected fuel pump as well. you CANNOT regulate 60 P.S.I. down to 5-6.

That is the number one hurdle most people choose to ignore when they want to change over. After that, you'll have to determine what fuel pump, and how you intend to supply that pump (at the pick up) with fuel.
It's not rocket science, I've seen some pretty cobbled up fuel systems that work. An electric pump needs to be mounted as low as you can get it, and at the back of the car (electric pumps "push" fuel, they do not pull it) If you run any new pump rated for a carb, then more often than not, you'll have to regulate that pressure down anyway (from 14-20 down to 5-6).
Holley's regulator is stupidly simple, and requires no return line. So in essence, one feed line and your done.

27.00 from Summit,...NOT 128.00.

What you do for ignition after that can be as simple as a duraspark, and either a factory box, or one of the aftermarket pieces from MSD/Crane/Mallory blah-blah-blh to trigger the ignition, and finito!!! you will have converted the car.

As far as reliability/cold starts/resale.....

Usually those few that offer negative comments here have never owned a car w/ a carburetor in the first place.

Carburetors did just fine for the first 70 years that they were used . The cars always started, in all temps,..and managed to go 100k miles at the same time.
I had a carb on the last project car. Complete conversion on a SOHC 4.6. The car started everytime, and managed to get 23 MPG plus. I'm on record 4 years ago making that statement after driving that car to MW. I drove it to Bowling Green in October.
One of those mornings the temp read 29 degrees. It also started right up.

Carburetors offset cold starts w/ an equally old school technology called a choke. Again,...probably the majority of the carb haters either never hooked it up, or disconnected it altogether as part of their "racer approved" mod regimen. No choke = poor starting performance on a cold morning,...but having one requires the following all to complicated starting procedure:

#1. Depress accelerator pedal completely to floor once.
#2. Turn key.
#3. Sit for 1 whole minute as engine runs long enough to "kick down" from choke cam.

If you can possibly be inconvenienced for that long, that a carburetor will work perfectly for you.

There are arguments across the board about the trade off/or the gaining of power when swapping a over to a carb, I cannot talk to that,..I try to know a little about what I comment on. But my overall instincts when considering that is to call it inconsequential in your case.

Resale on a SN 95 is a non issue.

Lastly,......purely from a tuning issue.

You only have to have the most minimal set of hand tools, some tuning skills,...(i.e. how to turn a screw driver,..how to assess whether the car has a stumble or bog, a friend to follow you to observe a WOT throttle pull, and a willingness to make the required changes to the squirters, jets, and power valves to fix what needs to be fixed.
If you buy the right sized carb for your engine, and use Holley's size recommendation chart for your engine size, and intended RPM band usage,...the carb will be so close right outta the box, you wont need to do jack.

In other words...A street driven 5.0 w/ mild mods, and a RPM band to 6000 only needs a 650 CFM carb MAX.

If however, you use the "Bufords guide to bigger is better carb sizing", and put a 750 DP on a 306.......you're gonna be one of those future guys that get on here and tell other people how carburetors suck.

jozsefsz · Dec 6, 2016

madmike1157 said:
Sigh,.......
You cannot run the stock fuel tank if it is your intent to also run the stock injected fuel pump as well. you CANNOT regulate 60 P.S.I. down to 5-6. Holley's regulator is stupidly simple, and requires no return line. So in essence, one feed line and your done. 27.00 from Summit,...NOT 128.00.

You absolutely can regulate down the stock pump to whatever pressure you want, provided that you use the regulator with a return line. The more expensive one. I've done it myself and it works just fine, lasted for years. The return line is already there.

You might consider 29 degrees cold, I consider -29 degrees cold. A choke can help get it running, but factory installed carbs even in the early 80's used stove-pipes and air inlet doors to get the air temperature to a serviceable range. On a really cold day you will have some driveability problems, and you will never run truly efficiently.

Resale can be a problem. Not that you'll expect to get double the money for an intact injection system, or that our cars are worth their weight in gold, but if you want to sell the old pile on eBay some day you've just eliminated 50% of your buyers who live in emissions-testing areas. I wouldn't consider buying a carb-converted SN95.

I agree with you on your high-level recommendation for carb size. I'd also suggest it be a vacuum secondary carb for a street vehicle and a manual choke (the electric ones are very unreliable in my experience). Personally I find changing jets, power valves, and accelerator pumps to be a LOT more expensive (those parts aren't cheap) and a lot more difficult than 30 seconds in front of the computer using a Moates Quarterhorse.

If you spend the few hundred bucks to get a decent old-fashioned vacuum-advance distributor and coil that part's pretty easy. One thing op didn't mention is if this was manual or automatic -- if it's an automatic you're going to have some problems with the transmission.

Possessed94 · Dec 6, 2016

Thanks for you guys responses. I will not be using the factory pump. I was going to use a Holley blue or pump of that nature. My car is automatic and I already have the Aod transmission for it, it's not the E transmission.

jozsefsz · Dec 7, 2016

The Holley blue is a nice pump, I run the red on my Mustang II. The blue may give you a bit more pressure than you want unless you also have a regulator (no return needed to go from 9 to 5 or 6 psi). It's a bit noisy though (read up on it, I mean hammering-noise noisy), and you're going need to figure out where to mount it, wire it, and follow the advice above about mounting it low and close to the tank. You'll also need to figure out the pickup inside the tank if you're not using the stock fuel pump. You'll need something like this: https://www.brothersperformance.com...ml?year=1996&gclid=CPbm0p2e49ACFcmPswodYU0GQw

Me, I'd go with the stock fuel pump every time.

Again, definitely not trying to knock your decision to go to a carb, that's your own personal choice. But once you add up all of the nickels and dimes to get carbureted you'll see why I frown on it. I have nothing against carbs, I've always had an old car around with one. But $300-$400 for a decent carb, $150 for a manifold, $100 for a distributor, $30 for a coil, $120 for a fuel pump, $100 for the pickup, and another $100 in odds & ends (air cleaner, valve covers maybe for a PCV delete, gaskets, hoses, etc.), removing the EGR system, dealing with the transmission (anywhere from $100-$1000+), and you're looking at somewhere between $1000-$2000 to net you zero horsepower at best, and the very real possibility of emissions problems and driveability problems. For that money you're most of the way to a TrickFlow HCI. Or a blower. Or an On3 Turbo system. You get where I'm going.

Carb Swap Fuel Setup(help Needed)

Possessed94

jozsefsz

90sickfox

Wasn't a pretty sight...and I've got big hands

Possessed94

Possessed94

CarMichael Angelo

my rearend will smell so minty fresh,

jozsefsz

Possessed94

jozsefsz

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Carb Swap Fuel Setup(help Needed)

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