Tail pipes - Team Camaro Tech
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post #1 of 10 (permalink) Old Apr 14th, 01, 04:08 AM Thread Starter
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I have a chevy 350 small block, mildly built, holly 600 cfm double pumper, eldebrock performer intake, with hocker headers with dual exaust 2 1/4" with glass packs. It is connected to the stcok 350 tranny and rear end. I replaced the exaust system about 2000 miles ago. I stuck my finger in the tail pipe, and it was coated with a light dusting of black dust. This dust was not wet, but enought that it completey covered my finger when I touched it. Anyways, the motor always has a gas smell from it and I am assuming it is running to rich and I get a lot of gas fumes into the cab. What should the inside of a tail pipe look like in my application?
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post #2 of 10 (permalink) Old Apr 14th, 01, 07:37 AM
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Sounds like your way rich.If your running very much cam,you have to set the idle screw in that it comes off idle circuit onto the transfer circuit of the carb,thus eye burning idle and mostly rich all the time.Holley tech line www.holley.com,had a neet fix for this,about drilling the primary plates to let air in so you can close the plates and get out of the transfer slots.this may not be your problem,but if it is its a need fix,worked for me

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55 Belair Sedan Pro Street 355 auto 9''
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post #3 of 10 (permalink) Old Apr 14th, 01, 02:46 PM
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You don't need to drill your throttle plates unless you're running a REALLY RADICAL cam, which you're not. Just start over from ground zero on the carb - turn both idle mixture screws all the way in (lightly) until they seat, and back each one out 1-1/2 turns. Fire it up and set the idle speed adjusting screw on the throttle arm to get a decent idle speed. Connect a vacuum gauge either to a FULL MANIFOLD vacuum port on the carb (NOT the "ported" vacuum pipe on the passenger side of the front metering block) or to the vacuum fitting on the intake behind the carb, and tweak the idle mixture screws about 1/8th of a turn at a time (adjusting the idle speed screw as necessary to keep correct idle rpm) until you get the highest steady vacuum reading. You'll have to work back and forth on both sides. When you've got the highest steady vacuum reading you can get, turn each idle mixture screw IN (leaner) about 1/8th of a turn and you've got it. Chances are your idle mixture screws are either set way too rich, or they're set way too lean and the throttle plates are too far open to compensate for it, and it's idling at least partially from the transfer slot, which makes it way too rich. Also check the little brass idle air bleed holes just inside the air cleaner ring at the top - if it's been run without an air cleaner, those tiny holes can get clogged, which will cause it to idle way rich.

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post #4 of 10 (permalink) Old Apr 14th, 01, 05:29 PM
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Drilling the primary holes will work even with the mildest cam,If you know what your doing.Its called custom tuning.Start with a 5 6/4 bit if this helps but still not perfect move up to next size larger. the secret is to not get the hole too big as to not have any control with main idle screw at throttle.If at normal idle you turn the mixture screws in toward seat when turned at 1 1/2 to 2 turns out and will slow down engine or engine dies this is probably not your problem.


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55 Belair Sedan Pro Street 355 auto 9''
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post #5 of 10 (permalink) Old Apr 15th, 01, 04:48 PM Thread Starter
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I am really not comfortable drilling our my carb. I thought you adjusted your idle screws as follows. Turn them in all the way. Back them out about 1 1/2 turn. Adjust them to maximun RPM is abtained (using RPM gauge not vacumme pressure). Then turn them in 1 turn (richer). I will have to try the way you suggested. I am used to Elebrock carbs.

Do you think I would experence any performace loses going to a Elebrock 650 cfm performer carb? I have a spare, and if I have to drill out the double pumper to make it work, this swap might be a better option.
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post #6 of 10 (permalink) Old Apr 16th, 01, 02:28 PM
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Since you have an eldebrock 650, I thought the only made 600 and 750 cfm carbs, I could be wrong, older ones might be 650.That would probably be your best bet,since you are used to tuning them,Performance should be close.I like holleys,but it took awhile to learn to tune them.I had a 600 eldebrock on a mild 350,ran it 4 years,never touched it,You wont do that with a Holley. Hope this helps.Gene

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post #7 of 10 (permalink) Old Apr 16th, 01, 05:54 PM Thread Starter
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Gene,

you are right. It is 600 cfm. It is about 3 years old. It is on a car that is not running at the time.
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post #8 of 10 (permalink) Old Apr 17th, 01, 02:45 PM
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When you turn your idle mixture screws "in" (clockwise), you're making it leaner, not richer. You can use the rpm method instead of a vacuum gauge, but the vacuum gauge is more accurate, as it shows variation better. When you get highest steady vacuum, only turn them in (clockwise-lean) about 1/8th of a turn ("lean roll" method). If you turn them in a full turn, you're ten miles off, way too lean, and if it runs at all, you'll have to jack the idle speed screw WAY up just to maintain idle speed, which will start dumping fuel from the transfer slot and your idle will be unstable and WAY rich.

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post #9 of 10 (permalink) Old Apr 21st, 01, 03:58 PM Thread Starter
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JohnZ,

With the vacumme testing method, do you still have to remove the vacumme advace from the distributer? I am thinking yes, but just wanted to make sure.
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post #10 of 10 (permalink) Old Apr 21st, 01, 06:57 PM
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Sounds rich to me, too....

Blk69, if you want, I can swing by sometime to help you out.

Just thought I'd offer.

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