Hey so i just joined so im not sure if im doing this right but i was just hoping i could get some help. So i just have a few questions if you could help me please. I have a 357 sbc and was going to order the carbureted vortech supercharger for it. Im looking at a goal of 550HP. But of course ive been doing alot of research and came across the fuel pump issue haha. Right now i have a Edelbrock mechanical fuel pump and of course i found the information on tapping into the top of the fuel pump in order for the fuel to raise with the boost. I have almost no experience with fuel systems so i feel that is not the way i should go. I was just wondering if i keep the mechanical fuel pump can i just add a boost referenced fuel regulator and be good or do i need to remove the mechanical fuel pump and run both an electrical fuel pump and regulator? if you could just help me, that would be amazing. Thank you. Any input or advice on anything would be great

So i have 350 SBC bored 40 over
- Speed Pro Flat Top Pistons
- World Products S/R Torquer Cylinder Heads - 67cc - .560 Max Lift
- Holley Street Dominator Intake Manifold
- Custom Chevy Logo Engraved Bolt Kit
- Black and Red Chevrolet Dress up kit
- High Volume Oil Pump
- Edelbrock Mechanical Fuel Pump
- Red 8MM Sparkplug Wires
- K12-464-8 XFI Hydrualic Roller Comp Cam - 113* lobe seperation - .550 / .546 Lift - Kit also includes Lifters, Springs, Locks, Seals, Timing Set, and Retainers
- 1.6 Ultra Gold ARC Series Aluminum Rocker Arms
- Mighty Demon 850 CFM Blow Through Carburetor
- Mighty Demon Fuel line assembly
- Magnum Pushrods
- Electric Water Pump
- Jegs Shorty Headers
- MSD Ready to Run Distributor
- MSD Blaster 2 Coil

Next step is to order
-Vortech Supercharger V-2 SQ SI Small Block Carbureted System
- Aeromotive 13301 Fuel Pressure regulator
- Bypass Valve
- Gasket Set
- Thrust Button and Wear Plate


Calculated Compression Test Results - From 9.2:1 to 9.6:1

I got the 9.2:1 to 9.6:1 with a calculation test on a Dyno Simulator program i have on my computer and i know its not exactly accurate, more of a rough estimate.

Number of cylinders - 8
Bore Diameter - 4.040"
Stroke Length - 3.484"
Combustion Chamber - 67cc
Head Gasket thickness - 0.045"
Head Gasket Bore Diameter - 4.045"
Piston to Deck Clearance - 0.00" - 0.20"
Piston Type - Flat Top
Dome Volume - Avg 9.60cc

Granted some of these numbers are estimates since i have not made exact measures yet. I was just using it to get an idea of what my compression ratio was. If you see anything wrong with it please let me know. thank you for the info.

I originally rebuilt this 350 with my father 8 years ago except it was a little different then, it had a Cam from a 383 stroker crate motor specs unknown, Holley 650 Carb, Original Distributor with Accel Coil, and the S/R Torquer heads came off of the 383 stroker as well but at the time had the original springs, pushrods, lifters and rockers. The motor is still built this way i just havent started the rebuild with all of the new parts yet. I got to drive it the day before i left for the army in 2009 and then it has been sitting ever since. My plan is to pull it out and rebuild it once again with the upgraded parts list above.

But im still confused about what to do with the fuel system once i get the supercharger??? I dont want to tap into the top of the mechanical fuel pump to make it work with the supercharger. Can i just get a Boost referenced Fuel Regulator and run the Mechanical Fuel Pump and it be ok. Or do i need to remove the Mechanical Fuel Pump all together and replace it with an electric fuel pump and regulator? Also can anyone please list what parts would work best if i do need to replace the Mechanical Fuel Pump? Or if you have any advice on this build or any input what so ever it would be much appretiated, Thank you all in advance if you can help me.

Please help me figure out what to do with this fuel system... And if you can recommend any products that would work great for my situation that would be great. Thank you

 

You're going to want to use an electric fuel pump and a bypass-style regulator with boost-referencing capability (a hose nipple on it that you connect to a point between the blower and throttle plates).

You can, in theory, do the same thing with a mechanical fuel pump by applying boost pressure above the pump diaphragm, but that's a little sketchy (gotta make sure that upper chamber is sealed except for where the boost referencing line comes in). I haven't heard of anyone doing that in years. You definitely can't just add a boost-referenced regulator to a standard mechanical fuel pump. When they hit their internally-regulated pressure limit (6-8 PSI for a typical performance mechanical pump) that's it- no regulator can make it go higher than that.

One suggestion I would make on the engine combo would be to drop the compression ratio with different pistons. 9.5:1 is a bit high for a boosted motor on pump gas. Lower is safer. And no, it won't be a total pig in the lower RPMs. There's an old 72 Chevelle I work on with one of my friends that's got a turbocharged/blow-through 383 under the hood (no intercooler, no meth injection). On pump gas it's gone bottom 10s and high 9s are within spitting distance for us. We run an 8.0:1 compression ratio. It's a lot easier to crank in another pound of boost to offset the slight loss of power from the low compression than it is to lower the compression ratio to stay out of detonation.

 

Thank you Damon for the input its alot of great information and you made it easy to understand. Would you recommend any specific fuel pumps or regulators for my set up? or a good set of dished pistons? Thanks again for the information!

 

You don't have to go nuts with the pistons. Almost anything forged with the proper amount of dish to hit your desired compression ratio will do. I've run a lot of Speed Pro (formerly TRW) forged slugs. They are heavy (require the rotating assy. be rebalanced) but they're tanks. And the price is right.

Fuel pumps you've got a choice of scillions of them. If you want to go high tech and invisible, get your tank converted over for an in-tank pump (A Walbro 255 pump would probably be sufficient for your application). For cheap you can use something as simple as a Holley Blue for a low-boost application (6-7 PSI max) since it poops out around 14-15 PSI (That's 6 PSI static pressure plus 6-7 PSI more to overcome peak boost). Since you're planning on using an Aeromotive regulator you might want to look into their line of pumps, too. We're using an Aeromotive A1000 pump and matching regulator in the Chevelle (along with -10 AN feed line and -8 AN return line). When we first built the system we figured it was more than we would never need. Now that we're knocking on the door of 9s it's looking like it's just about adequate.

 

Thank you Damon you really have been alot of help!! I've been up all night looking at different options and since this is going to be a long project for me, price isn't really an issue so i was originally looking at the A1000 pump / kit. Then i ran across an option that i believe to be pretty nice.

I was looking at the Magnafuel Quickstar 275 which has a
Pressure range of 4-12 PSI
Fuel Pump Included: Yes
Fuel Pressure Regulator Included: Yes
Boost/Vacuum Reference Port: Yes
Fuel Line Included: No
Fuel Filter Included: Yes
Fittings Included: Yes
Clamps Included: No
Max fuel pressure of 18 PSI
I'm going to run about 9 - 11 Lbs of boost, do you think this would work for me?
also i was going to replace the fuel tank on my camaro bc they arent that expensive, but since i will be using an external fuel pump, what do i do with the internal pump? Thank you so much again

 

Based on the specs of the pump and your boost rating, it would work. Barely. Only marginal because at 11 PSI of boost you would need 17 PSI of pressure (6 PSI baseline + 11 PSI of boost = 17 PSI of required fuel pressure. Right at the limit.). The pump itself is, otherwise, a monster.

I don't know anything about the regulator it comes with, but it looks like it would probably work since it's boost referenced.

NOTE: You will need to get at the existing in-tank fuel pump no matter what. Either to remove it so it's not a restriction to your chosen inline pump or to upgrade it and use only an in-tank pump.

IF you are going to do that, which requires dropping the tank (or doing the fuel pump access panel cut-out in the trunk floor- do a search), your best bet might be simply installing a monster in-tank fuel pump in place of your existing in-tank pump. Then you would need NO in-line fuel pump at all. Just a return-style regulator.

Here's the advantages of using an in-tank pump:

1. Super clean install. Nothing looks any different than before.

2. You can use the existing power supply wires to run it. Or you can run fresh ones in a design of your choice.

3. All in-tank pumps are designed for EFI systems so they can support much higher fuel pressures. 40-50 PSI or more operating pressures. When used with a carb system that only requires 6 PSI (or maybe 12-18 PSI under boost) they flow HUGE VOLUMES OF FUEL.

The very common Walbro 255 would be a bolt-in replacement for your stock in-tank pump but can EASILY support ~500 HP range in a carb/blow-through application. Need more? Walbro makes even bigger pumps now, too. A little modification might be needed to make these pumps fit, but nothing that's all that daunting. And it's all in an assembly you can work on on your bench. It's built into the pickup/fuel pressure sender assembly that installs from the top of the tank. All the achitecture and support brackets are already there- you just need to install a better pump and then drop the assy back into the tank.

And yes, an appropriate return-style regulator will pull 50+ PSI of EFI pump pressure down to a carb-friendly 6 PSI NO PROBLEM. That's the beauty of a return-style regulator. It's just a pressure diaphragm working against a spring. It'll regulate up or down to almost any pressure you want depending on the spring you have installed and the tension setting on that spring. Even the modest Mallory 4309 regulator, which is just a baby, really, will EASILY support a 500+ HP blow-through carb forced induction motor. THROUGH STOCK 3/8" FEED AND 5/16" RETURN FUEL LINES like your 87 probably already has.

 

Ok thanks again Damon for all the good information. And thank you for taking the time to help me!!

And yes i also noticed it would be very close to the limit so I've decided to move up to the next level pump. Which is the Magnafuel Quickstar 300 fuel kit. Which handles 35 PSI and also comes with the built in fuel filter / fuel pump combo and the boost reference fuel regulator. The inlet and outlet are both 10AN on the pump and i was looking at a braided flex line kit to replace all my old fuel lines. But the kit is 8AN, is that fine to use as long as i get the adapters that bring it from 10 to 8 AN. Thanks again i would be very frustrated right now if it wasn't for your insight haha. Thank you

 

For what you have planned, a -8AN feed line should be fine. The stock fuel feed lines is the equivalent of a -6AN.