Need advice on my Proposed Fuel System

[Screaming Metal]

As late in the system as you can get it.

One thing you need to remember is your system is only going to flow as much fuel as the smallest port in the system will allow. Use a Holley deadhead regulator and you might as well plumb your system with 1/4" line. You can run -16 line from the tank to the pump and from the pump to the motor, but if you end up stepping down to -6 or -8 line to feed the carbs, that -16 line has suddenly become reservoir and not massive supply. It will never flow more than the -6 or -8 line will allow.

I always recommend a bypass-style regulator and a fuel log, for high volume applications. Yeah, I hear everyone groaning about running a return line to the tank and a clunky-looking fuel log, but when you need consistent volume, this is the safest way to do it.

Plumb everything with minimum -8 line/hose/fittings. And stay as far away from 90° bends as you can. If you have to make a 90° turn, do it with the hose end and make sure it is a tube bend and not a forged-fitting bend. Lay your hands on some 1.750" aluminum tubing, a bit longer than the spread between your end-most carb fittings. Weld a couple of end caps to the tubing. Lay out some -8 adapter fittings along the run of the tubing as supply locations to the carb inlets. We're not looking for just a convenient way to get fuel to each carb inlet, we're also trying to get some additional volume as close to the carbs as we can. When you're finished, it isn't the prettiest piece you've ever seen, so have it anodized to "prettify" it.

Supply one end of your log with output from your fuel pump and attach your bypass regulator to the opposite end. Use a simple two port regulator and you can plumb a pressure gauge into the output port. As for recommendations, talk to Aeromotive and see what they have to help you out. I don't know if they will have anything that might already be boost-referenced, but I'm betting they do. And remember, it only costs a bit more to go first-cabin.

Remember a very basic point most people overlook or fail to understand. A 2X4 carb application is a lot easier to make happy than a 1X4 application, because you have twice as many float bowls to serve as mini-reservoirs for the fuel.


Which is why the drag cars that can, all use front-mounted fuel cells. And that is also where the fallacy of ginormous fuel lines from a rear tank leading forward comes into play. We think (erroneously) if a -8 supply line is a good thing, then -10 is better and -12 is even better yet. But when you remember the fuel in that line has mass, a -12 supply line can actually be worse than a -8 supply line. Because the column of fuel in that -12 line has more mass and is going to be even harder to keep moving under hard acceleration. For something capable of 60 foot times any faster than 1.10, -10 is about as big as you want to get with a rear-mounted fuel cell. Anything larger crosses over into the diminishing return range.

I love it when our Mike gets on the Jazz! Yes, he is right! More fuel in a long line = more weight, more weight in that line on take, a really fast takeoff, fights against that pump. I used to love the older dual feed lines on the older holleys, you could tap in and put a pressure gauge there, just ahead of the regulator. When we got cars to really hook up, I started leaving off the dual feed lines, putting a log between the floatbowels on each carb, with a really short line between the log and the floatbowl.

Remember, hydro-dynamic priniciples do apply here too! Remember, that liquid weighs roughly 7 lbs. per gallon. What I always try to do is place the incoming fuel linecoming from the front of the car, like from coming from the mechanical pump. that way as you get down, it helps. Anykind of serious car will have a rear mounted sump in their tank to help against such things. Street cars and Rods today run as fast as most bracket cars did in the late 60's and early 70's. Well, Bracket cars didn't come till later, but ya'll know what I mean! No, rear sumps aren't needed on the street, but its very easy this day and age to build a really fast car. Just add a blower and a bottle....and you might need these things. Hoosiers and 4 links, with a blower and a bottle, I almost guarantee you'll need most all this!

On a blown motor, make sure you keep your floats set correctly. It doesn't hurt to run your rear bowl floats just a touch high, or run some jet extensions or a rear bowl baffle. When you stand on a hi-horse blown smallblock, when you get on it, fuel has a tendency to run up the back of your bowl. If your making a 1/4 mile run in your T, (must of us get out of it the 1st couple of hundred feet!) When said fuel runs up the rear of that bowl, it uncovers your jets, and leans the carb out. This is a no-no on a blown motor!!!!!
A cheap solution, what I use, is a short piece of clear hose that fits over the jets and stays about 1/4 of a inch from the back wall of that bowl. That way, when you stand on it, it'll act like straws sipping that fuel thats standing against the rear wall of that float bowl!
And the guys running your carbs sideways, those baffles are a must....Most mild built blown 350's in our buckets won't need all this stuff. BUT, when it comes to running lean, I'd much rather spend a few hundred dollars looking cool with all this extra stuff on there, than to be trailered home with big, butt-ugly holes burned in the tops of my pistons.
*Blowers are unforgiving in 2 areas. Boost and carburation. Too much boost and you'll break things. Not enough in the carb dept and you can melt things. You can have a meltdown with either, if the circumstances are right. As long as you understand these 2 simple rules, that big aluminum lung will be your best friend!
AND DON'T FORGET TO CHECK YOUR OIL LEVEL IN YOUR BLOWER CASES!

I have alot of ashtrays around my shop that were once top-of-the-line Forged Hi-Tech Pistons that came outta motors that had blowers on them that were leaned out during a run on both the street and the strip!

 

[Screaming Metal]

Oh, by the way, if you put those pieces of hose of pieses of copper tubing over your jets to make those extension, be sure to check on your float clearance. When I do the copper ones, I flatten them out some so to get a little more room in there.