440 Fuel Issues

[303 Mopar]

Hey Team,
My 440 has a hesitation/cut out at higher RPM's around 40-50 mph at WOT usually in 2nd gear only when the engine is warm.  If progressively gets worse the more I run it, in stop and go traffic/hot days to the point I just feather the throttle to get it home.  When the engine is cool and within the first 15 min of running there are no issues at all.

I measured the fuel pressure at 3 psi so I switched to a higher flow mechanical pump from 440 (http://store.440source.com/High-Volume-Mechanical-Fuel-Pump/productinfo/138-1013/), blew out the fuel line (5/16" main, no return), and changed the rods and springs on my Eddy 600 cfm carb.  I plan to change carbs to at least 850 cfm when I get the funds.  I measured the pressure again and measured 5 psi when the motor was cool, then when it warmed up it dipped back to 3 and even 1.5 psi at idle.

Even though my carb is 600 cfm, I believe the issue is line or tank or sending unit.  I'm thinking of changing the sending unit to a 3/8" with a return, adding a 3/8" line and using the existing 5/16" line as a return line and change the fuel filter to a 3 port.  I greatly appreciate any and all ideas and opinions. Thanks!

[BLK 68 R/T]

Could be the rubber line that connects the sending unit to the main line sucking closed when it gets hot from the exhaust after driving, same thing for the fuel pump to fuel line hose. Also could be the fuel filter sock that is on the end of the sending unit.

[303 Mopar]

Could be the rubber line that connects the sending unit to the main line sucking closed when it gets hot from the exhaust after driving, same thing for the fuel pump to fuel line hose. Also could be the fuel filter sock that is on the end of the sending unit.

Thanks BLK 68 R/T.  The issue occurring only when the motor is hot is a mystery.  I replaced the rubber hose from the pump so I will check the sending unit too.  When I blew out the line I heard some good flow through the neck filler so I think the sock is ok, however I might replace the unit anyway.  Any recommendations on a unit with a return?

[Just 6T9 CHGR]

Im assuming when you swapped fuel pumps you made sure the push rod wasnt worn down?

[myk]

It would've been cheap insurance just to replace the pushrod.

It has to be that or the sending unit.  What else is there?  It's a very simple system.

Also, not that it should matter, but shouldn't the 'OP be running a 3/8ths fuel line? 

[BLK 68 R/T]

It would've been cheap insurance just to replace the pushrod.

It has to be that or the sending unit.  What else is there?  It's a very simple system.

Also, not that it should matter, but shouldn't the 'OP be running a 3/8ths fuel line? 

IIRC the 3/8 fuel line did not debut until 1970 for 440/Hemi cars. All others got the 5/16 line which I believe was standard on 68-69 big block cars.

As for where to purchase a good sending unit w/return...I have heard mixed reviews on them. I have not personally used any reproductions so I cant recommend one over the other for you. Hopefully someone else on here has experience with them and can steer you in the right direction.

[303 Mopar]

It would've been cheap insurance just to replace the pushrod.

It has to be that or the sending unit.  What else is there?  It's a very simple system.

Also, not that it should matter, but shouldn't the 'OP be running a 3/8ths fuel line? 

Thanks guys.  Unfortunately I did not check the pushrod. Since it runs great when cool and only cuts out/drops psi when hot, don't you think if it was the pushrod it would be a consistent issue?

Another friend said it could be the coil or gap between the reluctor and coil as he's seen the pick up breakdown with heat.  But I still keep going back to the gauge showing a big drop in psi when its hot.

[firefighter3931]

Read this :

http://www.dodgecharger.com/forum/index.php/topic,52284.0.html


Fuel pressure dropping = vapor lock 


Ron

[303 Mopar]

Thanks firefighter - I also found this article which is directly related since I have a 5/16" line and the car originally had a 318 and now has a 440.

http://www.hotrod.com/how-to/engine/mopp-0602-mopar-fuel-line/

[redmist]

It's the carb boiling over, and Vapor Lock....  Exact same issue I had. I tried everything in the book to fix it on my car. That was the driving force that pushed me to fuel injection.

Next time it does it, pull over and plug the vent on the carb with your finger... Watch the gas shoot out of everywhere as it percolates over!!!

[b5blue]

  Your on the right track, I cleaned and serviced my tank, installed a 3/8 pickup and made a 3/8 line, capped off the old 5/16 factory line and the return port on the sender and ran fine for years. Later I did just what to said and added a vapor can using the old 5/16 as return. I think the 600 is a bit small but would not go bigger than 750 really. Spacer to help with heat no doubt needed if running ethanol mix and 3lbs pressure might indicate clogged pickup sock to boot. (?)
  If buying a new pickup get one from Kramer Performance as he calibrates them to read accurately. (No point in fixing but having screwball fuel level readings.)