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Warlock1

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Discussion starter · #1 ·
ok, ok fuel system upgrade questionS...
Currently have 4.3 v6 with a Quadrajet carb, with mech fuel pump and 18 gallon alum tank. This boat hasn't been run for three years so I drained the tank and refilled with good gas. It would start and run the gas out of the carb that I poured in. I know it's not getting fuel and it could be the tank pick up, fuel lines, bad pump or just the filter in the carb.
Plan is to replace existing tank anyway with one that fits between the stringers or under new rear seat. That means all new lines as well. Now I would like to install electric fuel pump because I need the room on the side of the engine for the supercharger bracket and eliminate the ancient mech pump. Now that the history lesson is completed. What pump do you guys think will work? What size of lines? I will be using SS with AN fittings. Will I need a pressure rregulator or will the pump be able to do this? Anything else I am missing?
 
#2 ·
If you pressurize the carb you will pressurize the float bowls. Therefore you will have to run a regulator that will increase fuel psi 1 pound for every pound of boost therefore you will have to get a fuel pump that is capable of 6psi over your max boost. :bigsmile:
 
Discussion starter · #4 ·
Ok so I understand how an EFI fuel pressure system works when it has a return line, but how would this work?
Seems like I will need a 15 psi pump to be able to handle 8 pounds of boost. If I hook this pump straight to the carb will the pressure be too much for the inlet valve and force it open?
 
#7 ·
cfm said:
If you pressurize the carb you will pressurize the float bowls. Therefore you will have to run a regulator that will increase fuel psi 1 pound for every pound of boost therefore you will have to get a fuel pump that is capable of 6psi over your max boost. :bigsmile:
Click to expand...

Would you need to do this if the whole carb were in a box??


Doug
 
Discussion starter · #8 ·
Not Right - It won't be boosted right away. I plane on rebuilding the boat first. Installing the supercharger at low boost to make sure everything will work. Fuel, pulley alignment, oiling. Then pulling engine, installing blower pistons, working the rods, better heads and intake. Paint, powdercoat and chrome. Then dyno to make sure it is right and then turn up the boost and try to blow an Alpha drive :laugher: :laugher:
I have to admit when I got it started it sounded pretty good for a v6 due to the thru hull exhaust.
 
#9 · (Edited)
Boatally Insane said:
Would you need to do this if the whole carb were in a box??


Doug
Click to expand...
Yes.

In a naturally aspirated engine (remember: carbs are designed to meter off of atmospheric)The float bowls are vented to the atmosphere.
The fuel psi is the psi over atmospheric.
Our guages say '0' when at atmospheric psi.

With a carb hat or enclosure which both will pressurize the float bowls since they are inclosed : If you have 6psi boost you are pressurizing the float bowls to 6psi. So, if your fuel system is 6psi, guess what happens when it is exposed to 6 psi of air psi ?

Nothing. 6lbs against 6lbs = no movement whatsoever.

Not good. No fuel to the bowls.

So, back to N/A. We need 6psi fuel psi at all times.

Add in enclosure or carb hat from centrifugal supercharger where the float bowls are now not going to be vented to the atmosphere.

Say at WOT your carb will see 6psi.
To maintain a NET 6psi of fuel psi going into the bowl you will need 12psi fuel psi as measured in the fuel line.

12psi fuel - 6psi air pressure = 6psi fuel going into fuel bowl.

So, easiest way to do this is with a boost referenced fuel psi regulator. these are typically a 1:1 ratio.

1psi boost will raise the fuel psi 1 psi. These will cancel each other no matter what boost you go to.

Remember, you started at a base of 6psi fuel line psi so the net result will be a NET of 6psi going into the fuel bowl.

Note: Your fuel psi guage will not be installed at the point of entry where these two psi's will be meeting. It will be installed in the actual fuel line. Therefore you will have to have a boost guage and fuel psi guage (hopefully next to each other) to determine if you have correct fuel psi.

Ex:
Boost guage shows 6psi
Fuel psi guage shows 12psi
Cool - we have 6psi net! Let's keep the hammer down!

Boost guage shows 6psi
fuel psi shows 6psi
Crap!! Pull back the throttle now !!! ) Net fuel psi in the bowls. It's going lean now and the motor will eat itself. :angry1:
 
#10 ·
Find a complete takeout 350 Mag and drop it in. I have to believe it will be alot cheaper then a S/C setup.

PLUS,,,,,I dont think an Alpha will not hold up to an S/C motor.
 
#12 ·
Quad - forgot to mention Mach performance when talking last night. Was tired and knew the Pats would lose finally to the Colts. :shocked:

http://www.machperformance.com/forcedinduction.html

He does a ton of turbo and supercharger stuff with the 4.3's. Cams, heads, pistons, short blocks, etc,etc,etc,etc.

Haven't dealt with him (owner's name is Bill) so I don't know how much he/they will help you as far as advice on the engine build.

Worthy a try. Always better to go to someone that is in constant R&D and specializing in what you are trying to do. :bigsmile:
 
#13 ·
Is this a single 4.3 V6 application? Visit your local junkyard and buy the complete EFI off of a wrecked S10 chevy truck. With this you can tweak the EFI to make as much power as a supercharged 4.3 V6.

I used to have a Regal Commodore with twin V6 Chebbies in it that were carb motors. I yanked all the carb stuff, sold it on ebay and pid for the junk yard parts with the moeny I made on ebay'ing my old parts.

The result was a much better holeshot due to more torque of the EFI. My top end picked up 3 mph and my fuel economy went WAY up!

If you have a desire to SC your application in the future, you can do so MUCH easier with EFI and the tunability is simple. A 4.3 V6 with TPI injection, 1.65:1 roller rockers and a mild port job can make 300 horsepower without all the added weight of a supercharger and the needed headaches of now needing an entirely new ignition system with boost retard. An EFI setup from the Junkyard will COME WITH all the new ignition stuff needed.

Bet you could get everything you need from a local yard for less than $250.00 and some sweat.
 
#14 · (Edited)
Seeing as we know that v6 will come out and something larger down the road will replace it........


Line sizes I'd run:
-10 from tank to pump. (could prolly get away with a -8) Then -8 from pump to regulator. Then a -6 from each port of the regulator to each float bowl.
Try to stay away from forged 90 degree fittings and use a straight adapter with a bent tube style hose end when ever you can.

I just happen to know a guy who can hook up up with that stuff for a better then Summit / Jegs deal. ;)
 
#15 ·
If you are going to stay with an aluminum fuel tank, then why not build an in-tank pump setup? You can cut out a large enough top plate to secure the pump assembly and then use a t-angle aluminum mount to secure the pump and pickup sock in the bottom of the tank. I did this on my STV with a great success and spent less than $100.00 for the entire system.

You can now buy a 255lph fuel pump at Walmart for $45 and that is enough fuel to supply a 400hp turbocharged car let alone a 4.3L V6. I have twin 255lph pumps mounted in tandem, wired in parallel so if one pump should possibly fail, the other one will still keep the engine running without the possibility of leaning it out or chopping the tunnels closed at WOT.
 
Discussion starter · #16 ·
obnoxious - The price on that engine will be around 3500.00 I would guess with probably 250.00 in shipping. That still doesn't incleude the exhaust. I can supercharge and do all kinds of cool thing to the v6 for a lot less money and still hit the 300hp mark.
Blitzkrieg - how did you run the o2 sensors for the computer?
Also I am switching to a plastic tank, either under the new rear seat or in the floor
 
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Warlock1
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