emptying fuel bowls?

[Sneakin Deacon]

well i dynoed today, got to about 4-4.5k and went dead lean and died. its happened before aswell under longer acceleration pulls. only thing i can think of is the mechanical pump cant keep up...

so am i right in changing to a electric (going to anyways), or is there something else in the carb i need to look for

also, i was very rich up to that point, like 10.5-11:1 how do i go about leaning out the carb slightly under wot situations like that? im very new to carbs, so please bare with me :)

[Dano Moparo]

What kind of carb setup and ignition are you running?

[Sneakin Deacon]

holley 650, mallory distributor.

[Dano Moparo]

Crud in the lines and in the carb or some kind of restriction could cause these problems, if your carb/engine combo is a match. Electric pump and regulator as well as a larger diameter fuel line will get more fuel to carb.


If your bowls are empty it sounds like you need to adjust the floats. Pull the plug on the side of the bowl while its running and adjust the screw on the top of the carb until the fuel starts pouring out of the sight hole. Make sure you have a rag to soak up the fuel that will leak out. Holley make clear sights for the float bowls I had these when I had a holley on mine and they make it easy to adjust without making a mess of your intake. As far as the jet sizes go, it's trial and error. Usually down 2 #'s if your running rich and up 2 if your running lean, until you get where you want to be. Another thing that controls fuel flow and air flow on holleys is the power valve. I'm probly not the best person for giving advice on Holleys. I grew so tired of trying to tune that I finally gave up and went to a E-brock.



What's the rest of your engine setup, CID, comp ratio, cam

[Sneakin Deacon]

already running 3/8 line. and 7psi through the regulator, and have the clear sights for the bowls, the levels are fine.

at the moment, its a 260* cam, 355 with sportsman 2 heads. when i get this issue resolved i have a set of vic jr's, and a new cam, along with some gas.

[Dano Moparo]

You may want to try upping your fuel pressure to 8-8.5.

[Sneakin Deacon]

thats just a band aid though, that will just make me richer than i was before, and probably still be emptying the bowls.

[Dano Moparo]

Raising fuel pressure won't generally make your car run richer. Unless it's so high its pushing fuel past the seats. You say its rich at idle, but leaned out at WOT. Sounds like your engine is thirsty and demanding more fuel at load than the carb can supply. More than likely you have enough fuel pressure i was just thinking it was kinda low at 7 psi. I'm sure that your fuel/air mixture is the problem. This is an area that takes someone who is experienced with power valve and jet size combinations. There is a procedure that has you drill the primary butterflies and plug off the power valve. I can't find the bulletin yet, but I'm thinking it delt with this same issue. Wish I could help more.

[Sneakin Deacon]

i wont be plugging off the power valve id really be rich as hell at idle then, and the reason its going lean (and much further beyond that) is it has no more fuel to push in, just trying to figure out what could cause it.

[74javelin]

my friends car was dieing 300ft out and we thought it was running out of fuel. but he saw running out of air. we took off his air cleaner and it ran fine.

[Frankie]

Holley 650 on top of a 355 with that cam and those heads? It might not be enough carb. How high do you redline the engine?

[Dano Moparo]

Let's see if I can do this without getting longwinded. I'm pretty sure it's 3 different problems. Lack of fuel in the bowl with proper adjustment could only mean a fuel supply issue. You mentioned that you have a regulator on your system with a mechanical pump. If it's a stock pump I would do away with the regulator. Most likley at higher RPM's the stock pump push rod is "floating" causing your carb to starve for fuel. Your probly right on going to a electric pump, that should solve the supply issue.

Now running rich at idle. More than likely your idleing of the primarys. Try backing out the idle adjustment screw on the throttle plate. And then turn up the 4 corner idle adjustments evenly. Or you could open up the secondaries a tad while closing the primarys a tad. You can drill the throttle plate's for more air using a 3/16" bit and not eliminate the power valve. Eliminating the power valve is pretty much a racer fix.

Going lean 4500 rpm is probly the power valve. This could also be the reason of rich at idle also. If it's ever backfired on you, it prob took out the power valve. That 650 should have a 6.5 in it. I would go down to a 4.5 or 5.5.

All of this is assuming that you have no vacuum leaks. Sorry for stearing you in other directions, but not knowing all the spec's on your setup, what the car is used for (street/strip) and not knowing what you have already eliminated make a diagnosis hard.

[Sneakin Deacon]

i didnt say anything about running rich at idle, i said i was rich as hell up to about 4-4.5K in the run and then it went lean through the roof.

my idle is fine, im 14-15:1 at idle

i can get a solid 1st and 2nd gear pull in, once i hit 3rd it falls on its ass before i get very far into the rpms...now if im cruising say at 60 or so, and stab it in 3rd, itll pull all the way to 7000. the only time ive had the issue is during "track pass" style pulls.

already checked for vacuum leaks, everything is plugged off and no leaks are apparent but i havent done a smoke test.

this is a street driven weekend/track car. removing the power valve will mean i need to up my jets quite a few sizes to compensate at WOT and i may run into part throttle issues then. and it does have the 6.5 in it. but im pulling enough vacuum that it isnt open at idle. or light pedaling

[curtg21]

I would try the electic fuel pump first. I run a holley 650 on my 355. it runs great with the electic fuel pump and the regulator set at 7psi. Right now my jets are 73/77. Picked up 2tenths to 12.71 e.t.when I upped the jet sizes.

[Sneakin Deacon]

double pumper i presume?

[Dano Moparo]

If your confident on the carb setup as it seems, do the electric pump. I'm sure it just a fuel delivery issue. Are you running a high volume or stock fuel pump with the 3/8 line?

[Zman]

I ran a mech pump to 7600 on a 400 and set at 8 lbs, but I also had a light weight pushrod for the pump so it wouldnt cavitate. You need to check the jets also. Do you know what sizes they are. If you decide to run a electric pump, try running a return line. Makes the pump run a lot cooler and lasts longer as no load. The above advise on the power valves is also very good. Healthy 355 I would try to run a 750 also. Smaller carbs will also run leaner due to the airflow pass the venturies.

[Sneakin Deacon]

think i may have been running into vapor lock issues, the fuel line runs somewhat close to the headers, enough to possibly heat soak i think. i went to home depot and got some ducting for it, so maybe that will fix it. also picked up a holley black.

[???]

holly crap!!


Kenny just put a fuel gauge on it some where you can see it while driving and go make a pass...


go from there.