Carb problem

[ozrace]

well I stuck a 50 cc pump on the secondary side and finally got it to the track, due to some other issues did not mph or et as expected but car cam out of hole very well and did not stumble at all. Also tried out some MT radial et streets and got my best 60 ft ever and I haven't even started tuning them yet. techs are getting tougher at NED so before I can run again I need a tranny shield and a sfi flex plate, everything else was ok.
Len

Len
As Schmidtmotorworks said, at 30 feet the pumps shouldn't really be a factor. It is at wide open throttle and should be on the main circuit. To have to extend the pump shot that far out is a band aid for another problem.
I have worked with a lot of Demons and never seen one yet that needed a 50cc pump.
What sleeves do you have in it - gold?
I think you might have too much carb for your combo.
In relation to a Holley, a 775 (red sleeve) Demon will flow around 920 c.f.m.

[Len]

Carb pulls over 1" of vacume at 6500 rpm so in theory its not quite big enough. I do believe that on initial launch before the revs are up there that there is not enough flow thru the carb at full throttle to pull enough fuel so the 50 cc pump helps carry it until air flow is great enough.
Len

[ozrace]

Carb pulls over 1" of vacume at 6500 rpm so in theory its not quite big enough. I do believe that on initial launch before the revs are up there that there is not enough flow thru the carb at full throttle to pull enough fuel so the 50 cc pump helps carry it until air flow is great enough.
Len

1" Hg - That makes sense - sorry Len - I missed that.
I do think that if max RPM is 6500, and the stall is at 3500, then it should have enough signal to pull the fuel fairly easily without having to cover up the hole in fuel delivery with an extended pump shot.
Maybe there is something causing a poor signal at low RPM - most likely culprit is excessive reversion. Might be able to help it with an anti reversion cut on the intake valves, header mismatch to port, cam timing (open intake later), maybe smaller header tube.
Just some thoughts.

[bill jones]

-It sounds to me like the G force from the initial launch is sloshing the primary fuel hard enough that the engine is going gaggy rich, maybe even gets a slosh of fuel out of the primary vent tube.
-When the launch happens the primary fuel in the bowl slams the rear wall of the primary float bowl like a a huge wave and this pressure feeds the jets and pressure packs the main wells with positive pressure and at the same moment the engine is sucking so hard it siphons this fuel so easy it just momentarily floods the engine until the engine speed gets up to where it can digest all that raw fuel.
-So I would lower the float level about 2 to 3 flats at a time until something bad or worse happens.
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-You don't have to have a drag strip to test this, it sounds like you could do it any place where you had a hundred feet.
-How much electrical stuff changes at the moment you launch, like you have a timer on the trans brake that releases? the total ignition load needs something like about triple the amount of power to the sparkplugs when you suddenly go to wide open throttle so wide plug gaps could be part of the problem.
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-I've seen times where the huge G-forces will put enough force on ignition switch wires and electrical wiring that they'll move and if you have something like a loose contact on a toggle switch the engine momentarily dies.
-I've seen conventional lead plate batteries mounted longways in a drag car create niggly problems like this from the G-force grounding the lead plates against each other, and I've seen electrical shifter solenoids that use a ton of amps that will cause a car to stutter at the shift.
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-I've seen so many ignition switch problems that I won't even consider a single pole switch.
-I have used either a two pole or a three pole switch and connected the the poles together to give you either two or three swithes inside one switch housing.
-Same deal with crimped ends on the wiring.
-If you don't solder the wire to the terminals you'll likely will find one of these connections is bound to cause you grief.
-AND---where and how is everything grounded---that's as common a problem as there is not having the battery grounded to the COMPONENTS that are needing the electricity.