What would cause this? Car is 67 327 SB. Carb is Holley 3310. After returning from a drive, opened the hood to check something else with a/c removed and noticed fuel occasionally sputtering from accel jets with engine just sitting there. I have also noticed during drives lately a tendency for the engine to hover above idle and not return to 550 idle consistently. Up until lately, engine always returned to idle nicely and smoothly. Carb was rebuilt not long ago. What should I check?
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Re: C2 - Fuel squirts from accl pump jets on its o
Tim,
If your car is 300 HP and has a cast iron manifold there are two small 7/16" holes that carry hot exhaust gas under the carburetor and they need to be pluged with small freeze plugs, check the archives on this topic.
Also, there is a stainless shim type gasket that goes under the carburetor which is there to protect the aluminum carburetor from the heat caused from this exhaust gas. Sounds like the gas is boiling from heat and running out into the engine. Check out the assembly manual to be sure you have installed the correct gaskets and also check your heat riser to be sure it's opening properly. -
Re: C2 - Fuel squirts from accl pump jets on its o
Tim,
I had a similar problem on a WCFB and found that one of the floats was leaking causing fuel levels in the bowl to be way too high. And like you, the carb had recently been rebuilt including new floats - one of which was very slightly porus. Gas then found its way out through the path of least resistance which was by dribbling out of the accelerator pump nozzles.
If you wind up taking the carb off to check for the other suggestions, you may want to open it up, remove the bowls and shake them listening for fugitive liquid.
MIkeComment
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Re: C2 - Fuel squirts from accl pump jets on its o
Ball bearing (pump check valve) missing. It should be just beneath the nozzle. Be careful not to lose the gaskets. OK to re-use them. Try a small magnet to get ball out, rather than removing and inverting carburetor.
JoeComment
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Re: C2 - Fuel squirts from accl pump jets on its o
Tim,
If it is a 3310, you are probably a little oversized to begin with. Without the idle vent, I think I would follow up on post above about the heat slot and boiling of gas in the bowl.
Also, if it is a newly installed carb check for vacuum leaks in the base gasket, which would make you run a little hotter. Also, as above, whether you have the right gasket and baffle in place.
Jerry Fuccillo
#42179Jerry Fuccillo
1967 327/300 Convertible since 1968Comment
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Re: C2 - Fuel squirts from accl pump jets on its o
Oops, I mistyped my carb #. My carb is a 3810, the right carb for a 327/350 or 300 engine for 1967. Also, I have the alum intake for a 350 horse engine.
Regarding heat, the exhaust passage in the intake is open, but the heat riser on the right side is removed and spacer from FI car installed. So, it shouldn't be getting as hot as a cast iron intake or with heat riser.Comment
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Re: C2 - Fuel squirts from accl pump jets on its o
Sorry, my carb is a 3810, correct for the car. Alum intake.Comment
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Re: C2 - Fuel squirts from accl pump jets on its o
I wonder who's big idea it was to put those heated passage ways into the manifold. On my L36 aluminum manifold, it has those passage ways in there. I also notice in my gasket kit it came with stainles block off plates that were inserted to block the flow of hot exhaust gasses at teh surface interface between the head and the intake. I am not sure if the wanted you to completely block it off or partially block it off.
TerryComment
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Another thought
Tim,
Maybe the linkage is too tight against the pump lever or you have the pump cam in the wrong position. I can see where if the screw was too extended against the accellerator pump lever at idle you might be inducing some pump action from engine vibration. There is a clearance adjustment but at wide open throttle.
I don't think the aluminum manifold has a heat slot, but you can't discount a vacuum leak at the base of the carb. If you are seeing some overheating, it may be that your fuel is boiling into the air horn. It took me about a hundred miles on my 3810 with problems before my base gasket took a set, and I retightened the carb to manifold nuts.
Just a thought.
Jerry Fuccillo
#42179Jerry Fuccillo
1967 327/300 Convertible since 1968Comment
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Update with more data...
I did some more troubleshooting last night and found out some more info. I think the problem could be related to my throttle plates not always fully closing at idle. I will make a new post on that since it may or may not be related, but it seems that even though the plates close just fine with the engine off there is a tendency to hang slightly open with the engine running. This only happens when the throttle is slowly closed - not quickly closed. I found this as I was trying to figure out why during drives sometimes my idle hangs about 300 rpm high at traffic lights. It seems as though airflow or vacuum in the intake might be causing this? In any case, this may be causing the accel pump to "wander" a bit squirting a bit of gas. Just a theory.
Gerard: Regarding the accel pump adjustment screw. I have it adjusted per the manual, with .015" clearance with throttle wide open and pump lever held fully depressed. This is an odd adjustment to me, since it results in no clearance at idle position. The accel pump lever is held slightly engaged all the time at idle, but apparently it is supposed to be that way according to both the sheet that comes with carb rebuild kits and the service manual.Comment
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Re: Update with more data...
Tim -
That's the correct adjustment - it's done for two reasons; to ensure an instantaneous pump shot with the slightest movement of the throttle lever, and to ensure that the accelerator pump diaphragm isn't over-stroked and damaged at WOT.Comment
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