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Old 01-29-2013, 07:57 AM
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carb help

got my 350 back in my truck has a comp cam 268h 650dp carb hard to start when choke is close I have to open it even when cold whats the problem any help thanks

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Old 01-29-2013, 08:11 AM
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thats how the 650 dp works best. I found,when I used chokes on DPs,that I would partially close choke the choke,2 shots of the gas pedal,crank engine,engine fires,hold foot on gas,open choke most of the way,put in gear,drive away and open choke.
After a couple minutes car would idle,and smooth out with in 5 minutes.
I usually use single plane intakes and DP carbs,I live in Canada where humidity is very high on the coast.
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Old 01-29-2013, 08:26 AM
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carb help

Here is the PERFORMANCE CARBURETOR INSTALLATION AND ADJUSTMENT INSTRUCTIONS for the 650 DP. See page 5 General Information for choke adjustment. http://www.holley.com/data/Products/...7923-2rev1.pdf
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Old 01-29-2013, 08:33 AM
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thanks that's how I have Ben doing
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Old 01-29-2013, 11:03 AM
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I never used the choke on my 4777 carbs. I lived in FL then, so temps didn't get much below freezing. It's my all-time favorite carb, well, it and the Q-jet. It has to be one of the most flexible carbs out there, especially for a DP. I've had the 4777 on engines ranging from a 327 sbc to a 454 BBC including a Pontiac 455 and a Cad 472. The 3310 is also good, but I'll mostly always take a 4777. Bump the key and it'll light. Feather the throttle as needed until the idle evens out (a minute of running will do it). Not the best carb for mileage, though.

Bigger carb cfm can be stronger on the top end on the bigger engines (I gave up power on the BBC and Pontiac, I know), but for overall performance, it was a good carb even on them.
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Old 01-29-2013, 02:41 PM
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Thre is a difference between closing the choke some to enrichen the AFR and improve the metering signal for cold engine start up and warm up running and choking off all the air.

It won't run on just gasoline.
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Old 01-29-2013, 02:47 PM
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I have a double pumper and the choke was finicky, but I think thats just the set up demon runs. I eventually got her calibrated and it works as it should. You prolly need to hook up a vacuum gauge and wideband o2 and calibrate your carb. surely its to rich which doesnt allow you to run with the choke closed. adjustments are needed.
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Old 01-30-2013, 03:11 PM
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yes the motor had a big cam in it 292 300 dur now has comp 268H runs grate now lots more bottom end probably rich have not changed anything on carb it's so cold out I'm from Florida now in Iowa thanks for the help
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Old 01-30-2013, 03:56 PM
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carb help

You need to adjust your choke (closing of the butterfly) just enough to start the engine after pressing the gas pedal a couple of times. Then adjust the cable for the position the butterfly is in and to the wide open position. It's not going to be like an electric choke set it and it idles until it warms up. You will have to feather the gas until it will idle on its on. If you want a trouble free choke switch to the electric choke conversion kit. Holley Performance Products Choke Conversion Kit*45-224.
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