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Old 05-17-2010, 11:36 PM
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Car smells of fuel.

I had a 750dp built for me by Pro Systems recently for my 400 chev. After a couple of idle adjustments and setting the float level the engine runs pretty sweet with the carb as it is. It might be running a little rich though and has a small hesitation off idle when feathering the throttle by hand at the carb itself, cant really feel it when driving though. If I park the car in the garage after driving it and come back a little while later, the garage stinks of fuel! My float levels are set, so what else would make my carb smell so bad after use?

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Old 05-17-2010, 11:41 PM
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Are you leaking fuel anywhere outside the carb??

if its not

start it up and let it idle with the choke off. Look down in the carb with a light and see if the boosters are dripping fuel when its idling. Also check around for leaks, usually a strong gas smell is a leak or the carb is draining excess gas into the engine. If it is dripping, lower the float levels until it isnt dripping. Also shut it off and see if any fuel comes out anywhere inside or outside the carb.
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Old 05-18-2010, 12:51 AM
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No leaks outside the carb, engine is always pretty dry around the carb/manifold area. No choke on this carb either so should make it easier to see down inside it. Will try what you suggested and see what I find.
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Old 05-18-2010, 01:21 AM
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Sometimes lower quality braided fuel lines will saturate and leach fuel, causing a fuel smell.
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Old 05-18-2010, 01:38 AM
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Quote:
Originally Posted by Holdon
If I park the car in the garage after driving it and come back a little while later, the garage stinks of fuel!
You may be experiencing heat soak. Heat from the intake will travel up into the carb body after you shut the motor down, heating the fuel and expanding it so that it runs out of the bowl(s). Usually, using a carb spacer made from material that will not transfer heat does the trick. Best one I ever had was one I made from wood.
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Old 05-18-2010, 02:03 AM
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Quote:
Originally Posted by techinspector1
You may be experiencing heat soak. Heat from the intake will travel up into the carb body after you shut the motor down, heating the fuel and expanding it so that it runs out of the bowl(s). Usually, using a carb spacer made from material that will not transfer heat does the trick. Best one I ever had was one I made from wood.
You may be right come to think of it. Engine is always a bit harder to start when its hot, like there is no fuel there. I found if I let the electric pump run for a few seconds first and give it one small pump it starts easier. Only problem is I havent got any hood clearance to fit a spacer under the carb. I was just running it a minute ago and also noticed if I give it small blip on the throttle there is plenty of fuel squirting in but a delay in response. Only noticable with a small throttle opening though, response is fine if I crack the throttle a decent amount.
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Old 05-18-2010, 02:05 AM
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Quote:
Originally Posted by 68NovaSS
Sometimes lower quality braided fuel lines will saturate and leach fuel, causing a fuel smell.
Lines should be ok, I used a braided line kit from Summit
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Old 05-18-2010, 10:20 AM
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What kind of intake are you using? If it's stock gm you might be able to block off the heat passage that goes from the center of the head to the intake. They make gaskets that block the passage off to run cooler intake temps. The heat port I'm talking about was used to speed up engine warm up
and thermostatic choke control. It might help in your case with low clearance under the hood.
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Old 05-18-2010, 01:04 PM
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Im usung a Victor Jnr so heat passages are already blocked off anyway, but thanks for the idea.
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Old 05-18-2010, 02:15 PM
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If I park the car in the garage after driving it and come back a little while later, the garage stinks of fuel! My float levels are set, so what else would make my carb smell so bad after use?

This is why modern emissions compliant carbed cars have a a fuel vapour recovery system with charcoal canister to collect the hot fuel vapours that come off the fuel bowls vents during hot soak.
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Old 05-18-2010, 02:23 PM
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Do not evaluate the throttle response by blipping the throttle in neutral.
What is important is that the throttle response is correct when you drive it.

Incorrect idle timing will cause the carb's pri and sec throttles to be open beyond their sweet spot (idle fuel transfer slot exposure at idle) Results in less then optimium idle quality, poor off idle driving response and shortened spark plug life from fuel fouling.

Remove the carb and flip it over and look at the throttle blade edge. Should be around .020-.030" slot exposure at idle. More idle base timing allows you to close the throttles more. Less idle base timing requires more throttle opening. Lack of a PCV on any carb that has a 3/8" pcv port on the bass requires more throttle opening at idle to compensate. The carb is designed for the pcv.
The bigger than cam, the more timing at idle.
If the idle timing is not enough the motor will run hotter than it should and make the carb hotter, kicking off more hot fuel vapours when you shut it off.
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Old 05-18-2010, 02:37 PM
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sbc cooling:

drill and tap for a water port here
connect to the water bypass port in the top of the water pump
improved idle cooling on 400's especialy if you did not drill the
heads for the 400's steam holes.
some other manifold like the super vic come with this water port .
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Old 05-18-2010, 11:34 PM
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Quote:
Originally Posted by F-BIRD'88
sbc cooling:

drill and tap for a water port here
connect to the water bypass port in the top of the water pump
improved idle cooling on 400's especialy if you did not drill the
heads for the 400's steam holes.
some other manifold like the super vic come with this water port .
Thanks for that, I have to take the manifold off soon to fix a slight oil leek at the back of the valley, so might do that water port at the same time. My inlet/outlet for my heater comes through the firewall just above the manifold at that point so might even plumb it straight from the heater to the manifold.
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Old 05-19-2010, 02:47 PM
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If you need the heater it goes in this water circuit.
Top of water pump to heater, from heater core to drivers side rear manifold port. ( that you would have to add to your manifold.)
Many of the old factory GM manifolds (eg 64-65 corvette 327-375hp fuelie injection manifold) had this rear water port.
(GM eliminated this rear water port on the manifold during the "emissions era" as they wanted a hot(er) running motor at the time.
Many of the edelbrock and professional product manifolds have these rear water ports.
Makes a big difference in idle cooling stability on my 400sbc.
(No more thermostat /temp gauge hunting during warm up.)
more stable/ consistant overall cooling while idling and driving.
Try it.
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Old 05-19-2010, 02:51 PM
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Nothing stopping you from rigging up your own custom fuel vapour recovery system with charcoal canister and return lines , purge valves etc.
it is an effective system.
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