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Still having troubles with my 305. Need input!!

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Old Jan 21, 2007 | 12:24 PM
  #1  
HuggerI-ROC's Avatar
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From: Houston TX!!!!!
Car: 99 Mystic Green Trans am
Engine: LS1: Heads, MS4 cam, bolt'ons
Transmission: Fully built T-56 w/Spec3 & Pro 5.0
Axle/Gears: 3.23
Still having troubles with my 305. Need input!!

Well I got her running if only for a bit.
The carburetors accelerator pump jets were clogged
so I rebuilt the whole thing (edelbrock 1405 (600cfm))
it looked like it was working fine.

I had it running for 25mins to brake in my cam but it would pulse a little
500 rpms or so and would not idle under 1500 rpms. I noticed after shutoff
That the carburetors jets were still pushing fuel though. I blamed this on the floats I adjusted being adjusted to high and not closing the valves.
I took it off and adjusted them a bit lower.

When I try to start the car now it fires up but jumps into the high RMP
(2500 2800) holds for a second or two then drops to around 750 and dies.
I have little to no reaction from the throttle and I have moved the idle screw forward enough to keep it running at 900 rpms, but the engine shakes badly and it pulses up to 2500 rpms every few seconds (were the shake smoothes out). I have a small amount of fuel coming up from the accelerator pumps seal on top of the carb now. The fuel pump is the same as before the build. It has fuel it's just not applying it right. Also I need it running half decently before I can set my timing so that is making all this worse.

so the question
Did I rebuild the carb badly?


Would an carb not adjusted right, do this?

Is the car shaking badly from fuel starve at low RPMs or do I have a LT1 flywheel without counterweights (or would the shaking be constant throughout the RMPs)?

Also the smoke that come from the carburetor after shutoff is just vaporized fuel right?


I know I didn't go into much detail but I'm tired


Thanks for any input in advanced, JR
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Old Jan 23, 2007 | 11:05 AM
  #2  
HuggerI-ROC's Avatar
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From: Houston TX!!!!!
Car: 99 Mystic Green Trans am
Engine: LS1: Heads, MS4 cam, bolt'ons
Transmission: Fully built T-56 w/Spec3 & Pro 5.0
Axle/Gears: 3.23
anyone... a little help please
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Old Jan 23, 2007 | 11:13 AM
  #3  
sofakingdom's Avatar
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Car: Yes
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Transmission: Sometimes
Axle/Gears: Behind me somewhere
Sounds like the power brake booster hose or the PCV hose is disconnected. (huge vacuum leak)
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Old Jan 23, 2007 | 12:29 PM
  #4  
HuggerI-ROC's Avatar
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From: Houston TX!!!!!
Car: 99 Mystic Green Trans am
Engine: LS1: Heads, MS4 cam, bolt'ons
Transmission: Fully built T-56 w/Spec3 & Pro 5.0
Axle/Gears: 3.23
well the brake master is hooked up and all the carb ports a pluged.

any other ideas?

heres a picture from were it is leaks a little when running.

and a picture of the car with the scoop.
she needs a bath been in garage for 2 months.

Last edited by HuggerI-ROC; Jun 28, 2008 at 04:05 PM.
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Old Jan 23, 2007 | 12:34 PM
  #5  
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Car: Yes
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Some other HUGE vacuum leak.

One way or another, sounds like a huge vacuum leak.

Is there a port at the base of the carb, in the rear, for the brake booster line? (besides the one on the intake)
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Old Jan 23, 2007 | 12:35 PM
  #6  
HuggerI-ROC's Avatar
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From: Houston TX!!!!!
Car: 99 Mystic Green Trans am
Engine: LS1: Heads, MS4 cam, bolt'ons
Transmission: Fully built T-56 w/Spec3 & Pro 5.0
Axle/Gears: 3.23
yea there is a hole for the brake booster in the back of the carb and it's plug up.

any other ideas? all check anything.

Last edited by HuggerI-ROC; Jan 23, 2007 at 12:40 PM.
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Old Jan 23, 2007 | 01:23 PM
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Car: Yes
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Axle/Gears: Behind me somewhere
Carb base gasket.

Anything that can cause a HUGE vacuum leak. Look for a vacuum leak. You've got a vacuum leak.

Anybody can sit at their keyboard and type in the names of parts that can cause a HUGE vacuum leak. What have you done to find it? Have you sprayed carb cleaner around every place that there's vacuum while it's running, to see if it changes the idle speed?
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Old Jan 23, 2007 | 03:50 PM
  #8  
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Car: 91 RS
Engine: 350 vortec
Transmission: T-5
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he doesnt want to use carb cleaner ether would be way more fun for this exercise
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Old Jan 25, 2007 | 04:51 PM
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Car: 89 Firebird
Engine: 350 Ramjet
Transmission: 700R4
Axle/Gears: GM 9 bolt 3:27
Sounds like if you are sure you don't have a vacuum leak you may need to recalibrate the power mode in the carb. If I read some of your other post you have a different cam package. The Edelbrock 1405 has stepup springs under the the pistons that attach to the metering rods. The ones you have in there may be too heavy for the vacuum you pull at idle causing the rod to open the power port basically flooding the engine at idle possible explaining the vapor you see after it shuts off. Edelbrock spring kit #1464 is about 5 or 6 bucks they are color coded and you might want to try a lighter spring to allow the vacuum to hold the metering rod down at idle and dumping fuel like you had your foot in the secondaries.


http://www.edelbrock.com/automotive/eps_sect2.html

Here is a Edelbrock EPS carb user and calibration guide if you don't have one. Read the section on calibrating power mode. I know it doesn't seem right that it could cause an idle problem. I had the same thing on an Olds 350 with a W31 cam that wouldn't idle till I changed to a lighter stepup spring.
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