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Post by bustedknuckle on Nov 22, 2013 16:35:37 GMT -6
I can't get my engine to idle when it is cold. It has to be 140 degrees before it will idle. I've drilled holes in the primary throttle plates to increase the air. adjusted idle mixture for max vacuum even tried cracking the secondaries to allow more air.There are no vacuum leaks. It is very rich when it does finally idle. It is a holley 3310 carb on a 383. I think I need to open the idle air bleeds but I don't know what size drill to start with. There are no other problems with the carb or the performance of the engine. It just will not idle cold.
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Post by milkman on Nov 30, 2013 22:35:15 GMT -6
Since nobody is jumping in here, ill take a stab at it. I have a couple questions, if you hold the throttle at about 1500-2000 rpm when it is cold will it still die out or will it stay running? are you running gas? is your power valve blown? what size jets do you have? how far out are your idle mixture screws? two metering blocks or a plate on the secondary? what cam are you running? what is your base timing set at? without knowing these things its hard to say what is going on, but usually a cold engine tends to run leaner. Drilling holes in the throttle plates will make it leaner, opening up the throttle plates will make it leaner, if you open the throttle plates too much to where they go past the transfer slots, then it will not be running on the idle circuit anymore. If your performance is good like you said, but only the idle is rich you probably need to turn your idle mixture screws in some. It is also possible that your jets are too big. There are other things to try first before drilling out the air bleeds. (which will make it leaner)
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Post by bustedknuckle on Dec 1, 2013 9:06:09 GMT -6
It needs to run 2200-2500 rpm to stay running cold or it will die. running gas, 112 octane. power valve is not blown. jets 74 primary. 83 secondary. idle screws out 1 3/4 turns. two metering blocks no power valve in secondaries. cam, solid flat tappet .543 intake, .567 exhaust, 106 lobe center. 14* btbc base timing. When engine is cold it is so rich it will burn your eyes out in the garage. it is running on the idle circuit, the throttle plates are not open past the transfer slot.
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Post by milkman on Dec 1, 2013 10:45:41 GMT -6
ok, idle screws look like they should be in the ballpark, base timing looks fine, the cam specs that you have look alot like a speedway cam I used to have, is that about 255-265*@.050 duration on that cam? It runs at 2200-2500 rpm which means its not running on the idle circuit anymore at that rpm, so the problem is probably in the idle circuit. The idle air bleed passages might be plugged, have you checked if they are open? you can pull the bowl and metering block off and spray carb cleaner through the holes from the mounting surface on the main body to make sure they are open. Has it always done this or did it just start doing it all of a sudden? What vacuum are you pulling at idle? What size power valve do you have? If you are only pulling 5" of vacuum at idle and have a 6.5" power valve it dont matter if its blown or not it will be opening. your jets are not big enough to make it run as rich as you say it is running, I have run 82 in the primary on a 355 and it still idled at 1000 rpm. you have to have an air passage blocked somewhere or you are getting extra fuel leaking past somewhere inside the carb. Make sure the metering block gasket is in good shape and that its the right one.
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Post by bustedknuckle on Dec 1, 2013 11:19:31 GMT -6
It has always done this done this. I have tried different carb bodies with the same resaults. pulling 10" vacuum at idle with 6.5 power valve. the idle screws were adjusted for max vacuum. When I clean a carb before assembly I make sure all the ports are open and not blocked but I will check them again. Gaskets are always new even if they are the reusable ones. When the engine is warm I can't get it to idle under 1200 RPM without stalling.
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Post by hptuner on Dec 2, 2013 20:13:25 GMT -6
Have you tried a good-known carburetor & it worked fine?
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Post by motorman on Feb 15, 2014 12:34:19 GMT -6
if you have a cast iron intake with the heat risers blocked this will happen till the intake warms up to vaporize the fuel. fuel has to vaporize to burn correctly
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Post by flipflopoo1oo on Feb 23, 2014 11:15:53 GMT -6
TRY LOOKING AT THE BUTTERFLIES IN RELATION TO THE LOW IDLE CURCIT! YOU MAY NEED TO DRILL A 1/8-3/16 HOLE ABOVE THE SHAFT TO ALOW BACKING DOWN TO GET THE FLAPS BACK TO THE IDLE PORTS! I USE A VACUUM ADVANCE TO UP THE TIMING AT IDLE WITH LIVE VACUUM! ANY RACING ENGINE NEEDS 28-38 DEGREESE OF TIMING KEEPING IN MIND OF EXTRA FUEL NEEDED DURING THE RACE! I NEVER RUN A POWER VALVE TO CLOSE BACK JETTING WHEN YOU NEED IT MOST!83-86 WORKS FOR ME!35 YEARS OF WINNING PROVES THIS WORKS! IF FLOODING OUT OR TRY PLACING YOU HAND OVER THE CARB TO SEE IF IT HALPS OR HURTS WITH A HALF RESTRICTION! THIS WILL TELL YOU WHICH PROBLEM YOU HAVE! CLOSE THE MIXTURE SCREWS ALL THE WAY, ONE AT A TIME TO TELL WITCH SIDE IS WORKING! IF IT RUNS WITH THEM IN OR ONE IN YOU ARE GETING FUEL FROM SOME WHERE YOU SHOULDN'T! TRY THIS HOT AND COLD! If A VALVE ADJUSTMENT IS TOO TIGHT IT CAN MAKE IT COLD NATURED! GOOD LUCK FINDING YOUR PROBLEM!
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