Supercharged fuel system

[af2]

Just curious if when you dyno tested it if you measured vacuum at the carb at WOT max rpm...
To see if the 2 600cfm carb were are restriction to the blower.
Roots blowers like a BIG BIG carb(s) as it has to WORK harder to draw are thru a carb(S) that are a restriction (too small) That extra WORK take power. Make the blower work less hard give more crankshaft power to go fast.

Did you measure the carb vacuum @ WOT? EG 1"....1.5" 2" vacuum..

Bird at this point I think he needs to get it to the track and get the seat wet. I hope he runs on the west coast, I like the car. My 2 sons and I are going to build an altered next winter if the money Gods allow......

[F-BIRD'88]

Just curious if when you dyno tested it if you measured vacuum at the carb at WOT max rpm...
To see if the 2 600cfm carb were are restriction to the blower.
Roots blowers like a BIG BIG carb(s) as it has to WORK harder to draw are thru a carb(S) that are a restriction (too small) That extra WORK take power. Make the blower work less hard give more crankshaft power to go fast.

Did you measure the carb vacuum @ WOT? EG 1"....1.5" 2" vacuum..

Bird at this point I think he needs to get it to the track and get the seat wet. I hope he runs on the west coast, I like the car. My 2 sons and I are going to build an altered next winter if the money Gods allow......

He probably will Wet the Seat first time he hammers it... HA HA

[Mrhp]

Under the carbs was either .3 inches of vacuum or .03 at wot I can't recall, but I did check to see if the carbs were causing a restriction. I had read many of your posts before registering, and that was something always debated. The restriction causing the rods to drop and lean the motor out. These carbs have an orange 5 hg spring in them, so I should be o.k. It made 7.5 psi at 6000 rpm, and ran absolutely fantastic. I got the 1405 Edelbrocks from Allstate Carbs in N.Y. They were set up for a roots application as per Edelbrock as far as jets, rods, springs, and I am assuming needle valves. The valves weren't listed, but since everything else was done, I will take that leap. We made no adjustments to the carbs, or timing on the Dyno. The Dyno jockey said everything looked and sounded great, and he would not change a thing. So much for Edelbrock carbs not working on a roots blower. This is a pretty mild motor, but sure runs good. Hydraulic flat tappet cam, 7.7 compression, 1-1 on an old GMC blower and some truck heads. Certainly nothing cutting edge. I had lots of help from the fellas at 348-409.com as I usually hang there. I surely appreciate you taking the time to help me out. Af2 sorry man, this car will run at Union Grove Wisconsin, and possibly Kaukauna Wisconsin, as I live in the U.P. of Michigan. Those are the two closest tracks to me. And as far as wetting my pants F-bird88 , I hope that's all I do in them!!!

[af2]

So much for Edelbrock carbs not working on a roots blower. This is a pretty mild motor, but sure runs good. Hydraulic flat tappet cam, 7.7 compression, 1-1 on an old GMC blower Af2 sorry man, this car will run at Union Grove Wisconsin, and possibly Kaukauna Wisconsin, as I live in the U.P. of Michigan. Those are the two closest tracks to me. And as far as wetting my pants F-bird88 , I hope that's all I do in them!!!

Funny a 327 we built in 1982 using 350 pistons was still running until a year ago when a rod let loose. Ran and will run the same Carter 500 cfm carbs and use the same 327/ 350 piston .125" in the hole. It will use the same Isky solid z33 that it had before the carnage.
Hope to see your car on line. Like I said, get the tires off the concrete so they stay good.

[Mrhp]

I will get some steel under the tires, thanks for the tip.

[F-BIRD'88]

With .3" vacuum at WOT max output (less than 1" vacuum) I think you are good to go... ...I was just asking..

Even if it was 1.30" vacuum at WOT max output you are good to go....

(If it was 3" vacuum at WOT then larger carbs are called for)

But consider my recommendations of starting with a bit richer carb jetting at the track at least at first.
When the engine is in the car the best jetting is OFTEN, OFTEN OFTEN bigger than the best found on the dyno..And
you do not want to be caught with lean jetting on a Roots supercharged engine. (A little fat does not hurt and cools a bit)



Yes there is no reason Edelbrock cars cannot work real well on roots supercharged motors.
Especially the milder ones .. In my opinion they are more often your better choice as they are easy to tune and
trouble free. I like them on tunnel ram motors too..Again especially if its not a Prostock/Promod full race effort.
"street strip/bracket race/ Marine" stuff is just right for TWO Edelbrock carbs.

Good stuff. Post when you get some track time. Sounds like a fun ride. Thumbs up !

[Mrhp]

No, it was .3 or .03, less than one. Researching for the plumbing of the fuel system. I have lots to learn in that department.

[F-BIRD'88]

is this car going to have a alternator on it?

[Mrhp]

I would hate to ugly the motor up with an alternator, but I will if I have to. That is one of the reasons I would like a mechanical fuel pump. Less load on the electrical system. A mechanical pump would look more correct on a 60's built car, as long as the mechanical will do the job. I have considered using a driveline mounted alternator, if need be.

[Dave Koehler]

Considering everything else you have going on there, get a mag and throw the alternator, boxes and gadgets out the window.

[F-BIRD'88]

Just stick the alternator on the front of the motor and paint it black.
Make your life a lot easier.

[Mrhp]

Alternator=ugly.

[F-BIRD'88]

You'll get over it when charging batteries and poor 12 volt Battery only ignition performance etc etc gets old quick.
That engine driven alternator won't seem quite so bad.

You can "Low mount" it down near the crank with custom brackets and nobody will care.

While a good 6 valve high output (FLOW) engine mounted mechanical fuel pump can feed this motor
where they suffer is from heat soak reliability repeatability.
You may have trouble finding one with a static fuel pressure low enough for the Edelbrock carbs.
Edelbrock carbs DO NOT LIKE a lot of static fuel pressure. so a regulator with a return line may be needed.
Watch the inlet fuel FLEX hose on the mechanical fuel pump. Because the inlet hose is under partial vacuum (not under pressure) when heat gets at it it can tend to COLLAPSE and KINK or BOTH... Yup it will get hot. Then the fuel flow gets choked off.

The beauti of the Carter P4070 electric fuel pump is it is dirt simple and reliable. No regulator no return, 3/8" plumbing is fine.
Simple 3/8" in out inline automotive fuel filter... VERY 60's..
It flows a true 74GPH free flow and flows 63 GPH thru a .156" test orifice. (tested) (equal to 2x .110" needle seats Holley)
your test orifice is .187" so it will practily free flow at WOT on your twin carbs. (4 x .0935" needle seats)

The static fuel pressure is 5psi Just right for Edelbrock carbs.
Mount it right beside the fuel tank with a fuel filter between and forget it. Very 60's..

The alternator allows you to run your ignition box and boost retard box, fuel pump and any gauges reliably...

You could and will save a ton of money by adding a water meth injection system and run pump gas.
Racing gas will get old quick. $$$$$$$
The water meth injection really helps round to round performance CONSISTANCY, important in bracket racing
as the blower temp stays MUCH MORE cooler and constant. You don't need the big cool down between rounds.
You also do not need so much boost retard when using water injection. Roots blowers love it.

You can crank up the boost for more power, reliabily when you are ready for that,,, all on affordable pump gas.


It would be cool to get a big 110GPH 130 GPH 6 valve mechanical fuel pump and take it apart and tweek it so the static idle fuel pressure is 5 to 6psi at idle, so no regulator is needed.
http://www.sealsit.com Seals IT has a cool little heat shield for engine mounted mechanical fuel pumps.
http://www.sealsit.com/fuel-pump-seal.html

You can combine this with a sheet metal formed heat shield that mounts between the pump and engine to keep radiated heat off the pump and lines. Its about the install and heat management when it comes to engine mounted mechanical fuel pumps.


Where you run into trouble specificly in Drag racing with a engine mounted mechanical fuel pump is HOT SOAK while sitting in the staging lanes,,,etc etc ...When the fuel pump gets too HOT (and it will), the fuel inside boils. The pump cannot move the boiling fuel. Then the car coughs and ... shudders...You often see this at the drags right about the 330ft mark on a drag pass with a mechanical fuel pump. Its the HOT soak,,, YOU DO NOT EVER WANT to get into this on a SUPERCHARGED motor.
Interupted fuel flow on a Supercharged engine at WOT can cause instant engine damage.
One option is to PRE-feed the mechanical fuel pump with the Carter P4070 electric pump as it will PUSH any boiling fuel thru so the motor does not starve studder from hot soak.. This keeps the fuel pump inlet pressurized.
But then you might as well just eliminate the mech fuel pump.

[Mrhp]

Well I slung the mock up motor in the frame and low and behold, a mechanical pump will not fit, it hits the frame rail. I now have no choice, I get an alternator and electric pump. Oh well, thats the way it goes.This motor will always run race fuel and locked timing. As long as I tune for it, no problem. This car will never see any street duty, and only a few weekends a year at the track. Fuel wont be too bad. Now for an electric pump, bypass regulator, and plumbing!

[F-BIRD'88]

Well I slung the mock up motor in the frame and low and behold, a mechanical pump will not fit, it hits the frame rail. I now have no choice, I get an alternator and electric pump. Oh well, thats the way it goes.This motor will always run race fuel and locked timing. As long as I tune for it, no problem. This car will never see any street duty, and only a few weekends a year at the track. Fuel wont be too bad. Now for an electric pump, bypass regulator, and plumbing!

well there ya go eh... For the pump with your Edelbrock carbs try the simple Carter P4070...
Dirt simple .. flow test it for yourself thru the test orifice equal to the area of your 4 needle seats if you doubt my flow test.
If you don't like it return it... It has plenty PLENTY flow for your deal and is Dirt simple and very 60's.


Note it will actual flow MORE than my flow tests indicate when the alternator is running 13 to 14.5 volts DC
as my flow tests were done at 12 volt DC. The higher voltage with a alternator improves electric fuel pump performance.
Improves the ignition system performance too.