Minding my own business and felt the back tires rolling over me...
What is your fuel line size? Some AN-8 is not actually 1/2".
|Q:||Check Your Fuel Pressure!!!|
|A2:||Carburetors love fuel volume, but hate pressure. Pressure creates inconsistent aeration of the fuel in the float bowl, which causes inconsistent metering. Picture in your mind a water nozzle spraying into a bucket; the more pressure used, the more froth and air bubbles are created. If you have proper volume, the optimal fuel pressure is 4PSI for modern 2 and 4 BBL carbs. High horsepower drag care may not be able to run this low because G force works against fuel attempting to travel from the fuel cell in rear to carburetors up front.|
So now we have established that volume is critical. Let's examine factors that effect low volume, and there are many.
1st the obvious:
Fuel Pump capacity
Fuel Line size
Fuel Pump style
Fuel Pump placement
Capacity: Bigger is better. But… rating methods vary; some are rated with no output pressure or restriction. Others are measured at specified output pressure (A.K.A. 110GPH at 7PSI) (These ratings DO NOT specify the size, length, etc. of inlet of outlet size used.)
Line Size: Because manufacturer ratings fail to specify inlet or outlet size, we must assume the maximum size possible was used. Therefore, any reduction in size, no matter where it occurs, will reduce volume.
Beyond size, angles in fuel lines cause restrictions that reduce volume. Every 90° bend in the system reduces volume by 12%.
Example: Initial = 100GPH
1st 90° = 88GPH
Initial = 88GPH
2nd 90° = 77.44 GPH
Look at the fuel systems on most all vehicles, race, street, off road, etc. Almost without fail you will find at least 1 90° bend, plus 45°, 30° etc. More common you will find 180°, 135°, 90°, 45°, one after the other.
So your 100GPH, by the time it gets to the carburetor, could be as low as 20-30 GPH. This is why fuel pump manufacturers rate GPH vs HP at what seems a completely excessive ratio. They realize that they must consider a worst case scenario: to safeguard against the most unacceptable installation.
To look at this situation from a completely different standpoint, view the following; Cost of engine: $10,000 for 600HP, Cost of Minimum Required Fuel Pump: $200, Cost of Maximum Required Fuel Pump: $600, Differential = $400.
Possible cost of repairing damage to engine to lack of fuel volume is a minimum of $500 and a maximum of $5,000. By using the best possible component when designing your fuel system, you protect a much larger investment, give yourself peace of mind and invest in something that you can trust to grow with you.
My car was thought out and assembled by a non engineer (Me), so of course it works better.
Did you go with -6AN or --8AN or something else ? I assume external pump ?Yes. Engine was ran on dyno. I have the fuel curves.
The new inline filter and larger hose seems to have solved the issue. It had plenty of opportunity to run lean at ECR and never did.