Carb setups

i would go with a 650 demon if i was you. a electric chock would be nice since it is going to be a street car. if you run a automatic vaccum secondary's are nice. if you have a manual tranny you can go either way. If you are worried about fuel economy then go with a vacuum advance on your dizzy if not then mechanical.

I was thinking about a Holley 650 CFM #0-4777, an edelbrock ari gap #EDL-75212, I 've got Twisted wedge ... with a TFS cam stage 2 ... And its a 347 stroker

what ya think ? I was told to port my heads to get the best out of it ! but I'd like not to go that way. would it be good ?

I used a F cam Performer RPM heads, Performer RPM Air Gap, Holley 650 dp, 3.55's and I went 12.6@106 on seven cylinders. A collapsed lifter wouldn't let any air into the number two cylinder.

personally i would go with a 600-650 cfm but i would stay away from holley. I have a holley on my car right now and have had nothing but problems out of it. Keeps blowing power valves, and have had numerous of other problems, i'm about to change to either an edlebrock carb or demon...

curtisimo81 said:

personally i would go with a 600-650 cfm but i would stay away from holley. I have a holley on my car right now and have had nothing but problems out of it. Keeps blowing power valves, and have had numerous of other problems, i'm about to change to either an edlebrock carb or demon...

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My sentiments exactly. I used to have a Holley 600 that was a piece of S***T. It would blow power valves, flood, whatever. I had it rebuilt, only to find that it was a waste of money to do so because it STILL was a piece of S***T! I switched over to an Edelbrock 600, bought the tuning kit and was AMAZED how easy they were to tune. There's no power valve to blow out, they don't flood at all, and when you make a change such as a jet, metering rod, or step up spring, there's no leaking gas. I liked it so much, I use TWO of the Edelbrocks on my new setup.

Why not try a dual quad setup? People will be drooling on it at the local cruise night shows.

Here's my usual EFI to carb rant. There is some useful information if you don't get insulted by my remarks....


A word of warning on EFI to carb swaps: don’t expect to pass emissions in any state that does comprehensive smog inspections, because it won’t happen. You won't get any more power from a carb than you will from EFI.

Doing the swap: You must know how to read electrical diagrams and wire circuits properly to do the swap. Don’t take shortcuts or cut corners in the fabrication of the electrical or mechanical assemblies. If you do NASCAR quality work, the car will look good, run good and be as reliable as a carb’d car can be. Take pride in a job done with excellence.

If you do the hack job that is common among folks who don’t understand electricity or computers and are doing the conversion because it is easier than dealing with the EFI system, the result will look like and run like road kill. Wiring harnesses chopped up and spliced together with electrical tape, loose and dangling hoses, fuel lines spliced together with 3 types of fittings speak of ignorance and sloppy workmanship. If you can't do it right, don't do it at all. I wouldn’t wish a car with that kind of workmanship off on my worst enemy...

Now that the rant is over, here’s some practical advice…

Do not use an EFI in tank fuel pump with a carb. You will never get the pressure/flow regulated properly. Either go full EFI or use a tank/fuel pump/fuel lines out of an 84 or earlier Stang. Fabricating your own setup is possible but there are some snags to overcome.

Do not attempt to leave the EFI in place in an attempt to control either the electric fuel pump or ignition. Doing so qualifies you for the “Road Kill Mechanics Award”.

If you try to use your current tank, you will need to pull the fuel pump out and fabricate a pickup tube & strainer sock to replace the fuel pump. Or you can have a sump fabricated and welded onto you existing tank. Many welding shops will not weld fuel tanks because of the dangers involved if the tank isn't purged properly.

You will need an external electric fuel pump unless you change the timing cover for one with the mechanical fuel pump mount on it. Rip all the EFI wiring out, and the computer controlled fuel pump won't work. You will need to add a relay & switch and wire in the existing inertia switch for an external low pressure electric fuel pump.

You will need to run some new fuel feed lines or braided hose. The 3/8" aluminum tubing works well, but you will need a flaring tool and bending springs to fabricate the lines. Braided hose is easy to run and route, but is much more expensive. It is about $3.50-$4.00 a foot plus the end fittings, which are $3-$4 each. Fabricating hose assembles can be difficult, but anyplace that makes hydraulic hoses can do it for you for an extra charge. See http://www.amazonhose.com for more information.

While you are at the electrical part, you'll need a Durspark or similar ignition system. The EFI ignition depends on the EFI sensors to advance the spark. Rip out the TPS and MAP/Baro sensors and the computer will have no idea of the proper ignition timing for best performance. Running a fixed timing setting is only for test purposes or for a race track only car. Don't try it on the street: the results will not be nearly as good as a properly setup Durspark or equal. Crane makes a really nice distributor for non-EFI applications. . See http://www.cranecams.com/index.php?show=browseParts&lvl=4&prt=127 for more information.

does the air-gap and the 650 cfm will be too small for a 347 ?

I didn't have any problems with my Holley other than trying to get it to work when my car was stock. But when the heads and cam when in I had it all dialed in.

Hissing Cobra said:

My sentiments exactly. I used to have a Holley 600 that was a piece of S***T. It would blow power valves, flood, whatever. I had it rebuilt, only to find that it was a waste of money to do so because it STILL was a piece of S***T! I switched over to an Edelbrock 600, bought the tuning kit and was AMAZED how easy they were to tune. There's no power valve to blow out, they don't flood at all, and when you make a change such as a jet, metering rod, or step up spring, there's no leaking gas. I liked it so much, I use TWO of the Edelbrocks on my new setup.

Why not try a dual quad setup? People will be drooling on it at the local cruise night shows.

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What battery are you using on the passenger side? I do like the way the carbs look.

Hissing Cobra said:

My sentiments exactly. I used to have a Holley 600 that was a piece of S***T. It would blow power valves, flood, whatever. I had it rebuilt, only to find that it was a waste of money to do so because it STILL was a piece of S***T! I switched over to an Edelbrock 600, bought the tuning kit and was AMAZED how easy they were to tune. There's no power valve to blow out, they don't flood at all, and when you make a change such as a jet, metering rod, or step up spring, there's no leaking gas. I liked it so much, I use TWO of the Edelbrocks on my new setup.

Why not try a dual quad setup? People will be drooling on it at the local cruise night shows.

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What battery are you using on the passenger side? I do like the way the carbs look.

I'm just using a regular battery from Wal-Mart or Autozone (I can't remember where I bought it.) On the early Fox bodied stangs, the battery was mounted on the passenger side. My '81 hatchback has the same setup.

Racerjoey1 said:

I was thinking an electric choke. How does it work? When you start the car it automatically chokes it until what? How does it know when to turn the choke off? I've always wondered that. With a vacuum advance, where does it get the vacuum signal from? Is the carburetor equipped with a place to hook it up to? If you don't mind could you explain why a vacuum advance is better for an auto and a mechanical is better for a manual?


Sorry for all the questions. I understand a little bit about carbs and how they work but I like learning about how things work.

Joey

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Electric Choke: Before you turn the key, press the pedal to the floor and release to set the choke on the fast idle cam. When you turn the key, the car will fire and run up to 1500 rpm or so (you have to set the fast idle speed- the carb will come with instructions). The choke is hooked up to a 12v switched power source... As soon as the key is on, an element heats up the bi-metallic spring inside the choke, causing it to tighten up and gradually open the choke plate. In theory, the fast idle is supposed to step down 2 or 3 times until it reaches the base idle setting, but if you are running a throttle return spring like you should be, you will most likely have to blip the throttle to kick the fast idle off.

Vacumn advance: An Advance mechanism in the DISTRIBUTER that operates based on vacumn in the intake. Most strett dizzy's have both vacumn and mechanical advance, while some street/strip, and most race style only have mechanical advance.

As far as vacumn secondary or mechanical secondary (double pumper) carbs go, for a mostly street driven vehicle, especially one with an auotragic, vacumn secondary is the way to go... The rate the secondary's open at is easily adjusted with springs, and the secondary's only open as far as the engine needs... Manual cars can get away with double pumpers, and of course they are the choice for mostly strip cars... IMHO Vac. secondary's get a littlebetter mileage on the street.

I'm running P's with a 1087 cam, and a Performer RPM, and I LOVE my Holley 670 Street Avenger. That's my reccomendation. If you decide on a DP, a 600 would probably work great, no larger than a 650 though.