Need some carb help (Full Version)

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Need some carb help

Sweetness224 -> Need some carb help (3/27/2008 3:45:25 PM)
So my 81 vette has a crate 350 in it with a 800cfm carb (previous owner had the work done). Well i noticed it had a bog (almost like it was flooding out the engine) in it when you gave it an instant full throttle and i noticed the exhaust from the car had some black in it so it was running really rich. I took it in and had it tuned up and it runs a lot better now but there still is a bog at low rpms when you give it an instant full throttle. I was reading on car craft saying that a good size for a carb on a 350 would be 600-650 cfm or there are adjustments i could do to my current car like rejeting and so forth. I don't know a whole lot about carbs so any info on that would be very helpful and also if there is something else that im over looking that could be a causing this problem. There is about 2000 miles on the new engine so i didnt have any idea what it could be besides an oversized carb. What do you guys think? Also im looking at putting new weatherstripping on the car and was wondering if there is any tips or anything i should be aware of that might make my experience with this a little easier with less headaces. And one last thing... My antenna is stuck up and how do i go about getting it to go down. Would pulling the motor off and sliding it down manually work? It doesnt really matter to me to have it to pick stations up at the time. I'm going to be working on a sound sytem at a later time and will deal with getting it to work properly then. I just want to get it down so i can get a car coverly completely on it and so i dont get some idiot riping it off in the parking lot. Thanks ahead of time for all of your help! Blake

DeeVeeEight -> RE: Need some carb help (3/27/2008 4:47:38 PM)
I am not a carb expert either but it sounds like you are having a problem with the accellerator pump. My Holley 750 had a flat spot when I got on it and my mechanic ended up reworking the accellerator pump, he actually wanted it to deliver more fuel on acceleration. Can't help you with the antenna or the weatherstripping. [sm=icon_cheers.gif]

Sweetness224 -> RE: Need some carb help (3/27/2008 5:07:13 PM)
sounds like good stuff. How do i go about checking the accelerater pump?

78buckshot -> RE: Need some carb help (3/27/2008 5:38:38 PM)
Hi Sweetness224, the 800 CFM carb is more than the engine can use, 600 - 650 would be much better suited to the 350. Depending on the brand of the carburetor - Holly, Edelbrock, Rochester, some fine tuning may get you to a more decent running package. The accelerator pump is one area of the carb that can be tuned. Also the type of secondary throttle actuation (mechanical vs. vacuum) is a key component to drivability. Try to figure out what brand and type of carb you now have and get back with us. Many times in an attempt to produce more H.P., people will "over-carb" the engine, that is what your dealing with at this point. I'd think about a new carb. better sized to the 350.

C3 Starship -> RE: Need some carb help (3/27/2008 7:00:59 PM)
In my experiance, the carb tune and timing are crucial to smooth acceleration. And yes, I agree, sounds like your engine is over carbed. My 454 only calls for a 650 to 750 cfm. I could go to an 850, but then I'd just be wastin' gas.

Sweetness224 -> RE: Need some carb help (3/27/2008 7:30:02 PM)
Im away at school atm and my baby is back home in the garage but i 85 percent sure its an edelbrock. After your guys info i do think its over carb, anyone got a good suggestions on some good carbs to but on it, im roughly at 350-400 hp right now. I want something that would be good for drivability too but yet good power.

73shark -> RE: Need some carb help (3/27/2008 7:44:15 PM)
Here's some carb links: http://www.lbfun.com/Corvette/Tech/vettetech_files/Lars%20-%20tune%20a%20holley.pdf http://www.lbfun.com/Corvette/Tech/vettetech_files/Q-Jet%20Tuning%20Paper.pdf http://www.lbfun.com/Corvette/Tech/vettetech_files/Selecting%20A%20Carburetor.pdf http://www.lbfun.com/Corvette/Tech/vettetech_files/Carburetor%20Tech%20Info.pdf Haven't read all of these yet but here's my $.02 worth. You can get away with a somewhat oversize carb if it has vacuum secondaries. Since you said you get black smoke when accelerating, it sounds like the carb is jetted too rich. If you have a Holley, the accel. pump is tunable for shot size, duration, and how it comes in. Unless you are interested in racing, I'd recommend getting a Q-jet. They're easy to work on and setup. Good performance and economy. [:)] Of course that assumes you have a stock type manifold for spread-bore type carbs.

Sweetness224 -> RE: Need some carb help (3/27/2008 8:00:25 PM)
intake is a torquer 2 i beleive, at least thats what the local corvette shop said

73shark -> RE: Need some carb help (3/27/2008 9:08:40 PM)
According to Summit Racing, that is a single plane manifold which by design works best in the upper rpm band. Would recommend looking into a dual plane manifold for street use.

Sweetness224 -> RE: Need some carb help (3/27/2008 9:58:52 PM)
So swaping intakes and a new carb in the 600-650 cfm range should give me a lot better performance?

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