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Old 05-12-2004, 03:01 PM
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exhaust smells like gas

ok, I have a chevy 350 in a 72 chevy truck. all stock except for the edelbrock 750 carb, edelbrock performer rpm intake manifold, and hooker heads with 2 1/2 inch exhaust through dynomax bullet mufflers. exits 18 inches past the cab.
I've tried to fix the smell by leaning out the carb, but even when the motor is leaned out to the point of sputtering, the exhaust still smells like gas. What else could be causing this smell? I'm afraid to set it too lean because I don't want it overheating on me.

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Old 05-12-2004, 03:37 PM
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Is the engine running ruff? You may have to much carb for the engine. Does it backfire when the engine is revved up? Does it belch black smoke when you stab the gas? Also pull the plugs to see what they look like.

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Mark
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Old 05-12-2004, 03:46 PM
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the engine runs fine, I've got a little bit of an oil leak around the valve in cylinder number 8, and it only backfires when that spark plug gets fouled out with the oil. No black smoke, just a little bit of grey when first started on the passenger side due to the aforementioned bad valve seal.
I was wondering if it could just be because of how short my exhaust pipes are. Like maybe this is a normal smell, but I wouldn't notice it if I was running a normal exhaust.
Can't smell this in the truck by the way, only outside of it. Unless the wind is blowing just right.
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Old 05-12-2004, 04:11 PM
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Could have a bad power valve
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Old 05-12-2004, 04:22 PM
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power valve???
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Old 05-12-2004, 09:04 PM
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power valve is located in your carb...............regulates fuel flow if its blown your exhaust can burn your eyes and smell like fuel
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Old 05-13-2004, 08:12 PM
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The edelbrock style carbs (AFB style) dont have power valves

Just something to check but those carter afb style carbs like the edelbrock copy dont like much fuel pressure at all.
Get a fuel pressure regulator and guage and set it somewhere between 3.8-5.5 PSI ( I would start with about 4psi) and it will be a much better carb for ya.
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Old 05-13-2004, 09:45 PM
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i'd agree with the fuel pressure. too much will lift the needle off the seat. ummm, youve got grey smoke? normally oil smoke from bad valve seals(or any other burnt oil) is blue, and with a seal is only on startup or let down off high rpm. grey smoke... could be a slight head gasket leak, or a small crack... could be wrong though!
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Old 05-13-2004, 09:50 PM
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What is your ignition timing set at?
Maybe you have some dirt in the carb keeping the needle and seat from sealing?
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Old 05-14-2004, 08:15 AM
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initial timing is 10btdc, and at 3000rpm it's 37btdc.
it's an edelbrock performer carb, is that the same as the afb?
would going to a holley stop this problem?
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Old 05-14-2004, 02:58 PM
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yes the performer carbs can be a AFB style... numbers 1406 and 1407 are for sure the afb style (I know as I had those myself

Really they are good carbs for a nice street setup and offer good power when adjusted right....They are and never will be a holly 750 double pumper but they are still good carbs that you can set and forget that will support plenty of HP with great throttle responce.

Try the fuel pressure regulator and guage...summit racing and jegs both sell some for a good price in a kit.
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