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Old 01-20-2010, 03:56 PM
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Fuel System question

Hi,

I have few question....one of my friend have a 1949 Monarc 2 door coupe

His engine are a 383 dart block engine..dart pro-one aluminum head and 6-71 Blower wit 2 600cfm holley supercharger carb. the camshaft is a lunati with around 6800 rpm..

the blower run on 91 octan gaz...with the original 6-71 pulley (around 5 pounds of boost)

3.73 rear gear, 700r4 corvette transmission and 26.5 tall tire...

My question...

Does a complete 3/8 fuel plumbing system is enought to feed this engine ?

Second question...Does a Mallory 140 gph electric fuel pump will be enough to supply the 383 chevy engine...???

A friend of us..tell to him...that he have to change everything for a 1/2 fuel plumbing system....He already have braided Earl plumbing system..if we dont have the choice to change it..we will do...but if we can save money...it will be allright too....

Another question..

For the headers....on this engine...the headers is 1 3/4 primary and 3 inch collector...down to 2 3/4 exhaust...at the rear and 2.5 inch tailpipe...

Does the exhaust are too small....is that better to put 3 inch exhaust (double) from the front to the rear...

Thanks in advance to help me...

Stephane

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Old 01-21-2010, 10:10 AM
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If this is an all out race car then using 1/2" fuel lines will be better. But if this is a driver and cruiser then 3/8 lines are fine. The pump is fine as well just make sure you have a good filter coming from the tank before it goes into the lines and up to the motor.
I would run the exhaust as is too, again , if it's not a race car let it alone..........if it aint broke, don't fix it.
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Old 01-22-2010, 07:15 AM
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Quote:
Originally Posted by sunsetdart
If this is an all out race car then using 1/2" fuel lines will be better. But if this is a driver and cruiser then 3/8 lines are fine. The pump is fine as well just make sure you have a good filter coming from the tank before it goes into the lines and up to the motor.
I would run the exhaust as is too, again , if it's not a race car let it alone..........if it aint broke, don't fix it.
It's not a race car...but the guy want to have the best setup as possible....It's a street car..but when he go on the drag strip...put more boost on his engine and running race fuel...he dont want to miss fuel...or not want to loose power because of the size of his fuel system...

So the 140 gallon/hours fuel pump is allright ??? Perfect...If He dont need to change is exhaust system...perfect...

Just want to have a couple of other opinion from anybody...

Do you think everythins is allright..even if he put this tank (4000 pounds) car on the quarter miles...

Stephane
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Old 01-22-2010, 07:49 AM
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Quote:
Originally Posted by Ratoflic
It's not a race car...but the guy want to have the best setup as possible....It's a street car..but when he go on the drag strip...put more boost on his engine and running race fuel...he dont want to miss fuel...or not want to loose power because of the size of his fuel system...

So the 140 gallon/hours fuel pump is allright ??? Perfect...If He dont need to change is exhaust system...perfect...

Just want to have a couple of other opinion from anybody...

Do you think everythins is allright..even if he put this tank (4000 pounds) car on the quarter miles...

Stephane
With both the fuel system and the exhaust system, use gentle bends (exhaust should be mandrel bends!), NO 90 degree fittings or adaptors, no 'hardware store' fuel line fittings- their ID are often rough as a cob and will be found to be smaller than their size would indicate.

Earls or Russel make good fittings that take flow seriously. Not cheap- but less than an engine failure!!

Use a good pressure regulator and if possible run a return line so the fuel pump isn't against a dead head.

Be sure the pressure is adequate- at WOT. This may (should) take a helper to watch a hood-mounted temporary fuel pressure gage, or install a proper fuel gage in the cockpit that does not have fuel to it (you do not want any fuel lines inside the car for obvious reasons- even temporarily- EVER!).

AFA the tune- start w/a safe amount of ignition timing, and move up cautiously. A boost referenced timing retard is a VERY worthwhile addition to any boosted engine, IMHO. Again, not cheap- but neither is a bad guess. MSD and others can fill in the blanks on price, specs, etc.

Run the jetting on the rich side of safe. This can help the cooling and detonation control at the cost of possibly fouling some plugs in the process and excessive fuel consumption (big deal- this is a hot rod, after all! lol). Lean it as you gain experience w/what the plugs are saying to you.

Be sure the cooling system is optimized. There are many options as far as what type fan to run but if you're using a mechanical fan, use a thermostatically controlled clutch w/it. And a shroud.

Run the highest octane fuel you can, and when going to the track, try to get there with =/< 1/4 tank so you can dump some of their liquid HP in it. I wouldn't go crazy, but some high octane race gas mixed w/your unleaded premium would be good insurance, IMO.

Good luck and let us know how he runs!
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Old 01-22-2010, 08:05 AM
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Quote:
Originally Posted by cobalt327
With both the fuel system and the exhaust system, use gentle bends (exhaust should be mandrel bends!), NO 90 degree fittings or adaptors, no 'hardware store' fuel line fittings- their ID are often rough as a cob and will be found to be smaller than their size would indicate.

Earls or Russel make good fittings that take flow seriously. Not cheap- but less than an engine failure!!

Use a good pressure regulator and if possible run a return line so the fuel pump isn't against a dead head.

Be sure the pressure is adequate- at WOT. This may (should) take a helper to watch a hood-mounted temporary fuel pressure gage, or install a proper fuel gage in the cockpit that does not have fuel to it (you do not want any fuel lines inside the car for obvious reasons- even temporarily- EVER!).

AFA the tune- start w/a safe amount of ignition timing, and move up cautiously. A boost referenced timing retard is a VERY worthwhile addition to any boosted engine, IMHO. Again, not cheap- but neither is a bad guess. MSD and others can fill in the blanks on price, specs, etc.

Run the jetting on the rich side of safe. This can help the cooling and detonation control at the cost of possibly fouling some plugs in the process and excessive fuel consumption (big deal- this is a hot rod, after all! lol). Lean it as you gain experience w/what the plugs are saying to you.

Be sure the cooling system is optimized. There are many options as far as what type fan to run but if you're using a mechanical fan, use a thermostatically controlled clutch w/it. And a shroud.

Run the highest octane fuel you can, and when going to the track, try to get there with =/< 1/4 tank so you can dump some of their liquid HP in it. I wouldn't go crazy, but some high octane race gas mixed w/your unleaded premium would be good insurance, IMO.

Good luck and let us know how he runs!
for Right now..the fuel System is From Russel or Earl Company!...in 3/8. For the Igniton...We run a MSD 6BTM with all the MSD Stuff...

So for the size of the plumbing...if I understand well...its better to check if the pressure drop with the WOT ?

Its an Electric Fan with 3500 CFM, The radiator is a good 2 x 1.5 inch Row aluminum radiator (cross-flow)

Why a return line from the pressure Regulator ????

I have to ask him for the exhaust..I dont think he run 90degre stuff..but I have to look !!!
Stephane!!!
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Old 01-23-2010, 11:04 AM
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So far everything noted is pretty good. If there is more than an occasional blast at the track then the 1/2 fuel line and a return regulator would be in order. I'd also go with the 3" exhaust system and easy bends.

Now for adding more boost.... You will most likely drop 1-2 psi if you run open exhaust. It will probably lean out just a little too but it should run fine. I know it is very easy to just change pulleys and get more boost. However you can really mess things up quickly. I'm a big advocate of Air Fuel gages and learning to tune with them especially on blown motors. Before you go very far I'd look into this. Here is a good site.
http://www.innovatemotorsports.com/

You can also get this same stuff from Summit. Just key in the part numbers.

One other thing unless you have a very good 700r4 with proper TV cable adjustment, you will probably have some heart ache. Just my opinion.
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Old 01-23-2010, 12:10 PM
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You can answer your own question about the fuel system flow capacity and how much horsepower it will support by flow testing the fuel system on the car.

Flow test the system into a bucket or other container (maybe 1 liter or 1 quart) through a suitable test orifice that is equal combined area of the 4 carb fuel inlets needle and seats.

Time how long it takes to fill a 1 liter container and convert to gallons/HR (US)

http://www.barrygrant.com/bgfuel/default.aspx?page=81

You'll need minimum .5 LB per hp per hour fuel flow.
with supercharged motors you want to run a bit rich so add 20% to this minimum.

You will likely need to improve the single 3/8" system on this car.

If the 3/8" system is not up to the task after flow testing, you can double up with twined 3/8" systems (1 feeding each carb) or go with a 1/2" system.


I second the importance of tuning the motor using a Wide band AFR gauge.

For a 650 horse blown 383 I suggest a minimum of 65 GPH (US) fuel flow at WOT. The only way to see of your system will flow this thru your carb needle/seats is to flow test it.

horsepower x .1 = fuel flow requirement (GPH) at max rpm (US gallons)

Last edited by F-BIRD'88; 01-23-2010 at 12:23 PM.
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