This weekend I finished the installation of a new Fuel system. Many of you know that I have run a Carter 172 Mechanical pump the last 3 seasons running from the 11.80's down now to a best of 10.78 @ 125+. This is a great pump.

I didn't change anything for this year and the first time out 2 weeks ago I lost all fuel pressure at the eight mile point from hat would have been a high 10.70 pass based on the increments. The pressure picked up after a second of coasting and the car pulled hard again.

Fuel pressure through the traps registered 3 to 5 psi with the Carter. It would drop to 3 at the eight mile and then build up again through the traps with no feeling of hesitation over 3 full seasons of weekly racing and street driving. This year it dropped to zero though.

I did not find any clogs or debris wedged in any of my filters or lines of fittings.

The Carter was fed by a sumped stock fuel tank with -10 line and then -8 up to the fuel log.

The new system consists of the same -10 line to a Mallory 140 pump to a 4309 Return style regulator. from the regulator the fuel log iis fed by a -8 and the return line is also a -8. There are 3 log type filters in the system.

Fuel pressure has been set to 7.5 psi. First test will be this Wed night to see if indeed there will be a difference in ET or MPH between the systems.

We use the same pump with our 534' motor, no return line though.
It`ll do the job, no doubt.

Think the 140 will keep up better bc its electric or what? Im lost as to why youd go with less volume.

Originally posted by doggy69:
Think the 140 will keep up better bc its electric or what? Im lost as to why youd go with less volume. The flow ratings of fuel pumps are based on free flow and are as with anything often misleading. The Carter drops off in flow significantly faster as the pressure increases when compared to an electric pump such as the Mallory 140 at the same pressures.

I don't have a graph for it (Carter) but it is both pulling and pushing at the same time while the electric is only pushing.

I expect to maintain 7 psi through the entire run.

I am using the mallory 140, dead head regulator with all 8 AN line. Never a problem. Do you think the Carter is just starting to go away? I was thinking that I could keep the Mallory set up, and install a carter mech on it's own line from the sump.Use the mech pump on the street and use the mallory set up for a little nitrous action at the track :eek: . I will be interested in what your swap results show. I need to score an in car fuel pressure gauge, next thing on the list!!!! I do know that Ed is still using the Mallory 140 and stock 3/8 line on his low 10 ride. It should be plenty of pump!!

I took the 172 pump apart and it still looks brand new inside, maybe a check valve has strted weakining, I really don't know. it still pulled hard at 100 on the highway, but then again I wasn't going from 0 to 100 in under 7 seconds on the highway.

Originally posted by mc71454:
</font><blockquote>quote:</font><hr />Originally posted by doggy69:
Think the 140 will keep up better bc its electric or what? Im lost as to why youd go with less volume. The flow ratings of fuel pumps are based on free flow and are as with anything often misleading. The Carter drops off in flow significantly faster as the pressure increases when compared to an electric pump such as the Mallory 140 at the same pressures.

I don't have a graph for it (Carter) but it is both pulling and pushing at the same time while the electric is only pushing.

I expect to maintain 7 psi through the entire run. </font>[/QUOTE]So you think the carter is taking a dump. I was just wondering bc a carter 172 is $75 and Summits 140 gph system is $270. I don't have lots of money. But if its really better I could go with electric as everyone seems to be telling me.