Hot Rod Forum banner

1 - 3 of 3 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter #1
I have a mildly built 468, w/long tube headers running a heavier cam & a q-jet carb. When I really stick it on the road, it will kind of bog down on me and pop-pop-pop-pop. (Its also open headers since its too low to run proper exhaust on right now) I reckon it's my fuel pump that's the problem, its only a 50 GPH and I think my trouble is the bowl of the carburetor is being drained out faster than its filled. Was thinking a comp mallory 140 would be a decent replacement, however what would you recommend? Affordability/efficiency.

Car needs to be street-able and practical.



Any opinions on this?
 

·
Registered
Joined
·
13,478 Posts
Pump, maybe 50 gallons per hour is free flow delivery, add 15 feet of fuel line, put in a few bends and fittings who knows what the pump is actually delivering to the carb.


If I figure you can muster a horse per cubic inch at a half pound of fuel per horsepower per hour the pump needs to deliver about 38 gallons an hour. That strikes me is iffy with a 50 gal per hour pump, so maybe.


If this is an engine driven pump, these loose delivery rate past some RPM, you can see the evidence of this with a pressure gauge as almost for all pumps as they get above 4000 engine rpm you see a pressure drop. This tells you that the pump's max rated flow is at some lower rpm.


Compounding this is the Q-Jets rather limited bowl capacity which is going to be drained fast at a point where the pump is crapping out.


All that said, you can't rule out the carb being jetted or metering rodded too lean up on the top end. This might be a secondary metering problem stemming from jet or metering rod size or from the air valve adjustment or the cam that operates them.


Bogie
 
1 - 3 of 3 Posts
Top