Loss of power in the end of quarter mile

[Sixtyeight]

Hi,

Been running 1/8 miles with my restored '68 and rebuild and upgraded 440. It was doing real great. Won a lot!

Today I've been running the 1/4 mile for the first time. It runs great lots of torque and accelleration, (all in full throttle), but in the end it looses power, and almost stops running as if it doesn't get fuel anymore...If I take my foot of the pedal it starts to come up again and starts running again. He does this every time at the same moment. I use a high volume mechanical fuel pump.

Does this sound familiar?

For specs, take a look at: http://www.charger.nl/engine_specs.htm

BTW this is the car...

[firefighter3931]

Nice job on that car.  I like your engine build as well....very well balanced selection of parts. 


The fuel starvation could be a few things :

(1) float level on your Carb. With a Demon, the fuel level should be halfway up the site glass. Check that and correct if necessary.

(2) fuel filter could be insufficient for the application

(3) fuel filter clogged or partially clogged.

(4) fuel line has a sharp bend in it restricting maximum flow

(5) fuel pump pushrod is worn out and not providing enough stroke to operate the pump to full capacity.



What size fuel line are you using ? Is the fuel line all new ? New sending unit in the gas tank ?



Ron

[Sixtyeight]

Hi

Thanks for the reply, will supply more info;

1 float level is ok
2 fuel filter is the plastic mopar one, located between pump and carb
3 filter on the car for 5000 miles
4 no bends
5 can the rod be worned out in 5000 miles?

The fuel line is the original one that was on the car...


Jeroen.

[mikepmcs]

WOW, on the engine build.  That's all I got.

good luck solving your starvation issue.

What gear did you go to for the 1/4?


Nice car by the way!
v/r
Mike

[firefighter3931]

Hi

Thanks for the reply, will supply more info;

1 float level is ok
2 fuel filter is the plastic mopar one, located between pump and carb
3 filter on the car for 5000 miles
4 no bends
5 can the rod be worned out in 5000 miles?

The fuel line is the original one that was on the car...


Jeroen.

Ok, that helps :

(1) what size fuel line are you using ? If it's 5/16 then it might be insufficient for the stronger engine. There could also be corrosion internally which will restrict flow...even if it's a 3/8 fuel line.

(2) Is the sending unit in the gas tank original ? Was the "sock" replaced ? What size line ?


(3) how much fuel pressure are you getting at idle ?


It's possible that the fuel pump rod could be worn....there was a bad batch of fuel rods that made it out into the market several years ago. 

I would pull it out and measure just to be sure. It should be 3.25in long.


Ron

[Sixtyeight]

Hi, and thanks again!

1 I will measure up the line, and replace it anyway with a bigger one. Actually I should have done that in the first place...my bad.
2 The sending unit is the original one, with an increased filter and a new tank (so as clean as possible)
see pic . I don't know what mean by sock though?
3 pressure is around 7

I will also take the pump out and check it.

Jeroen.

[tan top]

 sock   means   the fuel filter   on the end of the  sender unit  pick up in the tank 

[Sixtyeight]

Hi,

One correction; fuel pressure is between 4&5 in idle.

The fuel line has an outside diameter of 5 mmm.

Jeroen.

[firefighter3931]

Hi,

One correction; fuel pressure is between 4&5 in idle.

The fuel line has an outside diameter of 5 mmm.

Jeroen.

OK, 4-5 at idle isn't bad....try revving the engine up in neutral and hold it there to see where the pressure stays. The pressure is fine but the volume of fuel could be insufficient for extended wide open throttle operation.

5mm is 5/16 if i'm not mistaken. Upgrade the fuel line and sending unit to 3/8.

Was the car originally a 383 or smallblock ?


Ron

[Musicman]

The fuel line has an outside diameter of 5 mmm.

5 mm... Are you sure about that    That's real small, more like brake line tubing   only about 3/16"
That would be Way To Small 
You might have enough gas in the carb to get you through the 1/8, but you'll be dry before you reach the 1/4 running at WOT

[Sixtyeight]

Hi,

you're right i measured incorrectly. It's 8mm.

Jeroen.

[Musicman]

That sounds better... 8mm is closer to 5/16 

[firefighter3931]

Hi,

you're right i measured incorrectly. It's 8mm.

Jeroen.

That's what i figured based on the pix you posted. I'm assuming this was a 383 or smallblock car originally ? 

I would install a 3/8in pickup and 3/8in supply line as the next course of action. 



Ron

[Musicman]

  Listen to the wise man.

[Sixtyeight]

Thanks, i will do so! Thanks for the advise!! 

Ron, it was and is an original 440 68 RT.

Jeroen.

[Sixtyeight]

Firefighter, you were right! 

It was the rod, it was 3.08 long. Luckily I had another one lying around (out of a '67 440) which was even longer than 3.25inch. I put it in and problem solved!!!

Thanks a lot for the advise!!

Jeroen.

[tan top]

 thats good it was a easy fix 

[firefighter3931]

Firefighter, you were right! 

It was the rod, it was 3.08 long. Luckily I had another one lying around (out of a '67 440) which was even longer than 3.25inch. I put it in and problem solved!!!

Thanks a lot for the advise!!

Jeroen.

Well....that was easy 

Too bad most fixes require more effort & Ca$h.   

Thanks for the update 



Ron