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Thread: how do you tune a carb?
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10-20-2009, 11:26 AM #1
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teal- 99 Z28 with an SS complex
how do you tune a carb?
I have a 63 nova vert i drive around right now. But it is now running like crap, i hardly drive the car around, so i know that attributes to it. But how would i go about tuning it, what would i need, over all to tune the car?
It has a 307, power pak heads, headers, and an isky 164 cam (similar to the fuel injected 327 cam).
Any help would be appreciated.
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10-20-2009, 11:47 AM #2
http://lmgtfy.com/?q=how+to+tune+a+carb
You need to be a little more descriptive in what you mean by running like crap. Also what carb is on the car now?
Will the car idle?
It also could be timing and not the carb?
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10-20-2009, 01:40 PM #3
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sorry, i am not sure of the carb, but i know the timing is off, i guess an overall tune. I would probably need to get a timing gun, does autozone have rentals on it. The car is running extremely rich, it idles fine after you get the juices rolling, it does have a pretty lumpy cam.
The car is running super rich, and the other gave me a few sputters.
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10-20-2009, 01:44 PM #4
Depending on the carb. If it's a quadrajunk, usually I turn the mixture screws in till she starts to stumble back them off till it quits and then back them out 1/2 turn further. Then thumb the throttle quickly and adjust till she snaps when I thumb it open and closed quickly.. Just be carefull not to bottom out the screws tightly, this can ruin the needles and their seats..
Last edited by Smittro; 10-20-2009 at 01:47 PM.
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10-20-2009, 01:49 PM #5
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when i get home today i will look at the carb to see what kind it is, then i will post up.
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10-20-2009, 01:52 PM #6
Also get yourself a timing light and see what she's set @ as far as timing. By power pac do you mean 1.94's or 2.02's? You may have to look up what your cam likes as far as timing is concerned..
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10-20-2009, 01:56 PM #7
Oh and a little heads up on old chevy's they will run 180* out. It will run badly but it will run. This has been the cause of many a head scratches for some guys..
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10-20-2009, 02:06 PM #8
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always dirty- 2013 Ram 2014 Caddy ATS
Could also need a rebuild. How old is the carb and what kind is it? If you are not sure a pic will let someone identify it.
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10-20-2009, 03:40 PM #9
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okay it is a 1405 maual choke edelbrock. It is a weber casting.
I am looking for the casting number on the heads but i can't find them, and so far my searching has not helped.
Underneath the carb is an edelbrock performer rpm intake manifold. i found specs on the cam awhile back but no luck right now, it is a isky 164 grind number i think
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10-20-2009, 03:42 PM #10
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i will also be looking at going by kragens and getting a light gun to check out the timing, i wonder if they have an A/F meter also that i could use, hmmmmm
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10-20-2009, 07:26 PM #11
for the carb here is the link from edelbrock's website
http://www.edelbrock.com/automotive_.../1000/1402.pdf
it shows where the adjustment screws are for you.
Found this for you too. This just states what Smitro said
http://neptune.spacebears.com/cars/stories/carb.html
LOL its even with the same carb as you!
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10-21-2009, 12:21 PM #12
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06 Jeep Grand Cherokee.- 02 superchipsZ28 M6(sold)
ah a 600 cfm too
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10-21-2009, 03:48 PM #13
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teal- 99 Z28 with an SS complex
this saturday i will tune it and see how it goes. I will post up what happens =).
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10-21-2009, 04:04 PM #14
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10-21-2009, 04:51 PM #15
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10-22-2009, 11:04 AM #16
You will need a timing light to tune that car correctly. You will also want to buy a vacuum gauge. You can buy a cheap dial back at your local parts place. Warm up the engine, drive around the block, or run an errand, just make sure the car is at operating temp. Disconnect and plug the vacuum advance to the distributor.
The only cam grind i can find from Isky is a 264. This is a .450 lift cam and should have 14-17 inches of vacuum in a 9.0:1 350 cid motor. If that is what is in your 307, you may have a hard time getting 12 inches of vac.
Set the initial timing at 12-14* before top dead center. Your idle speed should increase, unless your timing is too far advanced. Then turn down the idle screw until the car idles at 800 rpm. Turn the dial on your timing light to 35* and rev the engine to 3000 rpm, you should be able to see the 0* mark on the crank pulley. Adjust the dial until the 0* mark on the pulley is zeroed to the timing pointer. Read the dial, this is your total advance, this should be between 35-39*. Once this is set up, it is time to move on to setting up the carb.
Baseline the carb by turning in the bleed screws on the front of the carb all the way in until lightly seated. Now back them out 1.5 turns. Connect the vacuum gauge to a port that supplies manifold vacuum ( this will have a high reading at idle and will fall towards 0 when you rev the motor). Start up the car and read the gauge, you should have between 14-21 inches of vacuum at idle depending on your cam. If the car will not stay running, back out each bleed screw 1/2 turn until the car will idle (If you have to back them out more than 3 1/2-4 turns, your metering rods are too small and will need to read up on how to change them, or pay someone to do it for you). Pick one bleed screw and slowly turn it in until the engine starts to stumble. Then back it out until the vacuum reading peaks. Turn the screw out 1/2 additional turn. Repeat this for the other bleed screw. Readjust your idle to 800 rpm and you should be ready to roll. Disconnect your tools and plug the vacuum line back to the distributor.Last edited by cycowrencher; 10-22-2009 at 11:18 AM. Reason: are you sure its not a 264 cam?
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10-22-2009, 11:15 AM #17
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10-22-2009, 11:19 AM #18
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06 Jeep Grand Cherokee.- 02 superchipsZ28 M6(sold)
never used timing light
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10-22-2009, 11:29 AM #19
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10-22-2009, 11:36 AM #20
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06 Jeep Grand Cherokee.- 02 superchipsZ28 M6(sold)
meaning i never use them, not that i dont know how.
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