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06-15-2010, 09:49 PM
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#1 |
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Senior Member
 
Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Vaccuum Leak?
Ok, need some outside input for my little problem. Truck in questions is a 68 gmc, running a '70 402 and turbo 400. When I parked it last winter, it ran just fine. Started driving it again a couple of weeks ago and it would sputter through the carb. Tried adjusting timing, air/fuel mixture, etc but it still "backfires" through the carb really bad(worse now). I have replaced the carb gasket and the cap and rotor(HEI). I'm thinking a vaccuum leak somewhere but I have yet to find it. The truck also has factory a/c but I have check those two little lines. Any help is appreciated.
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68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi |
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06-15-2010, 10:12 PM
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#2 |
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Between Trucks...
Join Date: Mar 2002
Location: Los Angeles, CA.
Posts: 3,830
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Re: Vaccuum Leak?
Bad gas?
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Beat it to fit, Paint it to match... 
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06-15-2010, 10:33 PM
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#3 |
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Senior Member
Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: Vaccuum Leak?
Gas is fresh. And it definetly doesnt seem like fuel at all. I forgot to add that it will not idle in gear. It will idle fine in park and neutral, but dies as soon as it's put in gear.
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68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi |
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06-15-2010, 10:56 PM
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#4 |
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Registered User
Join Date: Apr 2010
Location: Kelowna, Canada
Posts: 116
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Re: Vaccuum Leak?
mine seems to do something like that..though ive not completely thought it was backfiring through the carb? When i give it gas and its still abit cold it gives off a bit of a "poof" then it almost dies out then it kinda smells bad in the cab for a minute then itll go away?
Not sure if i have the same problem but im curious Matt |
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06-15-2010, 10:58 PM
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#5 |
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Senior Member
Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: Vaccuum Leak?
ya it does it the worst when it's idling and you try to hit the throttle fast
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68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi |
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06-16-2010, 11:15 PM
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#6 |
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Senior Member
Join Date: Jan 2002
Location: Williston, ND
Posts: 2,999
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Re: Vaccuum Leak?
Ended up being super nasty fouled out plugs. Runs like a champ and that posi is oh so sweet.
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68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi |
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06-16-2010, 11:19 PM
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#7 | |
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Big Red - Now its a SWB!
Join Date: Jun 2009
Location: Oroville, Ca
Posts: 1,624
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Re: Vaccuum Leak?
Quote:
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68 3/4 ton  (Project)-350 Small Block, .030 over, 10:1 comp, 3998993 heads, C3BX edelbrock intake, comp cams XE268, Holley 670 SA, long tube headers, dual flow 40's, E-fan, Alum rad, currently under the knife getting shortened and bagged  build thread41 3/4 ton (wife's)-flatbed, fully restored to original01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's |
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