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Old 10-15-2005, 10:40 AM
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backfire and air coming out of carb

thaks for your interest. i have a 68 cmaro 327.i live in houston tx. without an a/c. so i havent been driving it much lately if u can imagine. i dont know if thats part of the problem or not, but it was running fine a month or two ago. now when i accelerate i get alot of back fire andair gasps out of the crbarator. i run it down the road and get alot of hessitation and back fire. it stars up fine and runs fine but when i accelarate it doesnt resond right away.and air pops out the carb.or might it be the timing? temp. is fine oil pressure is good. what might this be wna what can i do about it. thanks

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Old 10-15-2005, 11:08 AM
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Sounds like a couple fouled plugs to me.
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Old 10-15-2005, 12:56 PM
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check the plugs, check the timing and check to make sure the valved are adjusted right...
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Old 10-15-2005, 12:58 PM
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I had problems with my big block backfiring earlier this summer,checked plugs wires changed dist cap made sure the wires werent hooked up wrong,come to find out it was the bronze dist gear that was worn and causing it to backfire so it might not hurt to check it also.
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Old 10-15-2005, 03:10 PM
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It could be that your camshaft has given up. The bump stick needs lots of oil after sitting for any length of time and if you let it idle after not running for say two weeks or more then the lobes on the shaft will wear down quickly, that is why when you buy a new cam the instructions have you run the engine at about 1800-2200 at first so the oil will be bathing the lobes with lots of oil. If the engine idles smooth and you have checked all the other electrial problems and they are ok, then you will need to pull off a valve cover and start the engine. Using a timing light look at the movement of the rocker arms. Look closely at the exhaust valve rockers I think you will find that they are only moving a VERY small amount. So at idle the exhaust gasses can get out of the engine with no back fires out of the carb. But as soon as you give it some gas the valve doesn't open wide enough to get rid of all the burnt gasses. So when the intake valve opens a reverse flow of air and a popping sound come out of the carb.

Good Luck
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Old 10-15-2005, 06:04 PM
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Doc here,

Pull and invert the cap, check to be sure you don't have Condensation inside the cap, as well as carbon trails..check for undetermined life forms growing inside the cap..clean and dry as required...

Another thing is you may have a stuck valve...from sitting all summer, check to see they all move full travel up and down..

Vacuum Hose rot and fall off just sitting, do a visual inspection for that, and run it and spray carb cleaner around the manifold for leaks everywhere it speeds up, you have a leak (be sure the air cleaner is on..or it will false trigger)

if it is a Points type of ignition, the points may be too tight, check the gap, should be around 17 thousand..

The ignition capacitor could be going bad test that just pull it off and drive it..if it runs better, get a new one.

Qjets get loose just sitting, tighten all the bolts down , and do the air horn too from the center out..(it can warp) change the fuel filter inside the fuel inlet on the carb and any others you may have..

Check to see your PCV isn't stuck or sticking open..

Leaking or failing EGR valve can produce the same result if so equipped..

My suggestion is do a FULL tune up and visual inspection, since it's been sitting anyway, which will address 90% of these problems..Do an oil change and filter (the oil may be too thin to pump lifters now)

And don't rule out the possibility that the gas may be bad or contaminated..

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