Had this issue for some time (years) but never addressed it. Here are some details: Timing ~21 initial 33 total, in at 3200, ~ 11psi vacuum at 900 rpm idle, no vacuum advance Manual 4 wheel disc's, 13" front 12" rear Scott Brown cam slightly hotter than a TA413, on 112 center TA SP1 intake, with a 850 Biggs double pumper (not choke), center floats Have rubber hose on both front and rear vent tubes about 1 1/2" overall height Holley has whistle vent and floats are right at bottom of hole Fuel pressure is ~6.2psi with electric pump in tank Ported `73 455 heads, 11:1 compression and shorty headers, 3" exhaust TH400 with PTS 3200 stall and 3:42 It will do it if I'm running on E or full tank It will do it in drive or neutral. I can double foot it when in gear to keep it running. Use to do this at the drag strip to keep it running after the burnout. You can tell from the list I've tried a few things, yet no solution...
My AED 1000 did that and AED told me it was normal. They said the fix would impact performance. I believe they told me at the time to run the rear bowl level a little low and that would help. Curiously enough, my carburetor has not done that in years. I only use it at the track though.
Yep. Typically float-related. Adjusted wrong, maybe float is getting heavy. Wouldn't hurt to assure that all baffles in the float bowl are in place.
You can't wonder if it is dying do to going rich or lean, you need to look down into the Carb when it stalls out to see if the throttle blades are wet from going rich. In general if the motor will start right back up and or also needs one pump of the gas to do so then it's definitely going lean on stopping! If it takes 5 to 10 seconds of cranking to restart the motor then your going rich on the primary,secondary side or both. It also helps to make triple sure that your idling equaly off of the primary and secondary side of the Carb, and doing so without the throttle linkage hooked up to take that out of the picture.
Just out of curiosity, try putting it in neutral then slamming on the brakes when coming to a stop to take the torque convertor and engine load out of the equation. With this test its just the engine and inertia left.
Sounds float level for sure......sometimes a rubber hose between bowl vent with a breather match in. This will allow proper atmosphere pressure to the bowls but if fuel sloshes up some it give it room to go without going right in the motor. The 6.2 psi is slightly low too, a little higher pressure will help keep the bowls full with the lower level setting. Mine is 7.5 psi
Had this happen to me a few months ago. After checking all kinds of stuff I rechecked my floats, levels good, so I lowered the secondary down a bit lower that normal, then all was good. I switched from a brass float to a plastic and I set the plastic to the bottom of the hole, this is how my problem started.
6.2 psi is low for full throttle yes, but I found out some 25 years ago by jerking / playing around with my fuel system once I installed a fuel pressure gauge that with a AFB , Qjet or a Holley Carb that 4.5 psi is plenty of pressure to cruse 65 mph on with 3700 pound car with a 600 hp motor!
I only show around 3.5 psi full throttle in my 350 GS with a RobbMc pump, 1/2 pick up, and line, with my AED carb. At first it concerned me, but after thinking about it, if the gauge is still showing pressure, the bowls are still full, if the bowls are less than full, the gauge wouldn't show ANY pressure.
Mark this is not exactly a true statement. See your gauge measures pressure at that exact point in its location........what's happening behind it we dont fully know. It is possable that since the biggest restriction in the system is the needle and seats, that because your seeing a I'm assuming a several psi drop that even though your not running out of fuel yet, the bowls are not completely full, just not empty enough to cause an issue.........the fact your seeing 1/2 the normal pressure is a good indicator you fuel system is playing catch up. When you lift after a pass how long does it take for the pressure to come back up??? If it takes a few seconds that again shows the system built pressure back up. If pretty instant it will show the bowls were pretty full still. I believe in using the largest needle and seats possable to make certain the fuel has the quickest way possable to get in
Good discussion so far! I've got a business trip this next week so will try some of the suggestions when I get back. At least yesterday I got my brake balance adjusted, using the Wilwood proportioning valve. All four will now lock up with the front just a bit sooner than the rear.
The gauges you see in the engine compartment react to heat I believe, so the readings are not dependable once the gauge heats up. Not sure if liquid filled makes this worse. That leads me to question the value of such gauges, maybe just for setting the regulated fuel pressure when the engine is cold?
So far as I know, liquid-filled gauges are BY FAR the worst for inaccuracy after temperature changes--although I've never played around with gauges that use isolators. The secret to liquid-filled gauges is that they MUST be either "burped" or vented to be accurate when the temperature changes. They all have a rubber plug, either burp the plug before taking readings; or if there's no risk of dust/dirt/contaminants entering the gauge, poke a little hole in the rubber. Some plugs are molded with a nipple that can be sliced to provide a ready vent.
I used a electric set up on my Blower since I want the gauge in my dash cluster, and when I was running duel AFB Carbs the send was right at the inlet to the first Carb.
Sounds like fuel slosh. On the street I used to lower the float levels and it would go away. At the track I would raise the floats.
