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Old 11-15-2012, 08:56 PM   #11 (permalink)
 
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rough idle

P.S. In park, I can bring idle down to 500rpm, and it is still smooth as silk!
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Old 11-15-2012, 09:54 PM   #12 (permalink)
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Your byline says 'Texas' - where at? I'm in the Dallas area...

You could fatten up the carb you have just by putting in larger main jets - you shouldn't have to swap carbs. CFM capacity will limit how much total air the engine can breathe, but even if it's pulling a significant vacuum against the carb at WOT it should still be possible to get the mixture right. Surging is another indication of a lean mixture...

"Fuel jet" - "air jet" --- unless that's a carb unlike any I've ever seen, there ain't no such thing. Both the screws on the front of the carb are idle fuel mixture - they control how much fuel the idle passages flow when the idle circuit is in operation. There are two of them because there's one for each of the two front "barrels" - they both control fuel flow and should be set close to the same on both sides. How much air the carb passes at idle is controlled by a combination of the carb's internal passages (some Qjets and others have what is called "idle bypass air") and the idle speed screw that is adjusted to hold the throttle plates very slightly open. Above idle, fuel mixture is controlled by main metering jets inside the carb - they're calibrated orifices inside the carb. You have to take it apart to change them. Once the carb is above idle, the two screws on the front don't affect anything.

Why is it smooth in Park and not smooth in Drive? Simple - in park there's no load on the engine.

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Old 11-15-2012, 11:01 PM   #13 (permalink)
 
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Right! I termed "fuel" jet as the one on the fuel inlet side-the other as "air" side incorrectly (trying to clarify only made matters worse)- When I adjusted the passenger side mixing screw, it changed rpms. Not so on the drivers' side. No change at all. What would this indicate? Also, if I were to change the metering jets(and rods), how would I determine which size is best? I can have this carb pulled apart in a matter of minutes, but surely with my luck, it couldn't be that simple. I'm very comfortable working on a carb, and follow the instructions to the letter, although I feel like I'm in a nail biting suspense movie, with malevolent twists and turns designed to intrigue and perplex the helpless victim. I can't help but feel the durn new metering components would cost as much as a new carb. All this stuff seems to be insanely over inflated, for the cheesy junk they actually are. ANYhoo, we're located in Texas City, just a sight down the road, as the crow flies from y'all.
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Old 11-16-2012, 12:46 AM   #14 (permalink)
 
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rough idle

This just occurred to me-(I'm rustier than an Edsel in a swamp)-that when I had this carb apart, one of the fuel inlet needles seemed to be sticking a bit.(Has 2 floats) As I blew through the fuel inlet and lightly held one float shut, the other needle would sometimes not open unless I blew extra hard, and sometimes I'd have to manually dislodge it. The opposite needle would open and close with ease, never binding at all. This was a brand new kit I put in it-all new needles & seats,etc... Could never find the cause of that. I just pulled the plugs again- 4 looked a little black(not terrible), 4 looked slick as a whistle. Seems like that would explain why one of the idle mixture screws is not functioning. Or is the blow test not valid? Or am I way off base? Thanks again.
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Old 11-17-2012, 01:07 PM   #15 (permalink)
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I don't think you're off base ---- I'd find and fix the cause of that sticking problem before moving on to anything else.

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Old 11-17-2012, 03:43 PM   #16 (permalink)
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X2: always fix KNOWN problems first. Both idle screws need to be functional!
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Old 11-19-2012, 12:22 AM   #17 (permalink)
 
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Originally Posted by geeteeohguy View Post
X2: always fix KNOWN problems first. Both idle screws need to be functional!
This!! I can't shed any insight on your issue, being a carb newbie myself. I installed a Holley from hell and still have a vacuum leak to plug..fix what you know then deal with the next issue (if it's still there).
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Old 11-21-2012, 12:02 AM   #18 (permalink)
 
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Do you know your camshaft specs? You may need a higher stall torque convertor.
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Old 11-21-2012, 05:19 AM   #19 (permalink)
 
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rough idle

I believe the PO said the cam was stock. Not too sure about the converter either. All I know is the PO said he could really "smoke 'em." AND even as bad as she's runnin', I don't have to even push the pedal 1" quick to chirp 'em. I moved the vacuum advance line to the ported fitting and brother, she really LOVES that! I only mashed it to the floor once (very briefly- I don't want to hurt those new tires quite yet-the power is there).The hesitation it had at WOT is completely gone! I tore the carb back down again (#3)& re cleaned. The left side idle mixture screw is finally starting to show signs of life.Still a problem there though. It will affect rpms only at the last half turn of the screw to the closed position, though. I've cleaned those passages till I'm blue in the face-they seem clear. I believe it might be those vacuum blocks at the back of the carb-When I ran the carb this time, she surged about 8 times, then was idling better. I played with the lines at the backside, then it loped and the idle went down to about 600 rpm-(always had a little tick-thought it was lifter noise-but that went away also-sounded better than ever-got in the car and put it in gear and for 9 glorious seconds, it was sweet and smooth in gear. Then it loped. Then it surged. Then it ticked. It's gotta be a vacuum thing. Is there a good sealer for those metal threads? while I'm at it, I'm running 7147 metering rods on this Carter 9635sa. Whats the best way to determine the best sized jets, rods, springs,vacuum pistons, for this 455? THANKS.
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Old 11-21-2012, 01:41 PM   #20 (permalink)
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For sealer on threads, I always use teflon tape. Have you fixed that one sticky float problem yet?

As far as tuning, I recommend the tuning paper by Lars. It's for QJet's not Carters, but the same principles apply. In broad terms, you start with the idle mixture, then part throttle/cruise, and finally WOT/max power.

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