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Topic: rebuilt carb, whistling sound and idling high and small pops/backfires

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Re: rebuilt carb, whistling sound and idling high and small pops/backf (15/25)
 11/6/17 4:47pm
Target30
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1973 350 T-tops


Joined: 10/16/2017
Posts: 31

yeah, that would have been helpful!  haha!  so you are the winner!  i backed that off a bit, and then played with the idle screws, they are now at 1.5 out.  oddly, it seems like when i turn them in, the idle gets faster... i did read about a smog version(or something like that) that would follow this.  either way, its idling at 8-900rpm and fairly smooth.  it never was the smoothest thing, plus i was a kid when i drove it before and never really thought much more than "is it running?  yes, then drive!"
if i drop it to 600-650rpm, it really feels like it is going to die.  i've read that where it should be, but under 800 and i'll be on the gas pedal to keep it running.
getting tires this week, going to get it on the road!
Thank you to everyone for your help!  every little piece of information helped and now i can say i have rebuilt a carb, and the car actually ran afterwards!  haha!
Re: rebuilt carb, whistling sound and idling high and small pops/backf (16/25)
 11/8/17 12:59pm
Target30
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1973 350 T-tops


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so i got new tires, and took her for a spin last night, in the dark because no plates yet!  i live next to a small school, so i just pulled out of the driveway, in to the school parking lot, went around once or twice, then back home.  i need some more carb work!  did well out of the driveway, a little sputtering up the small hill to the school.  literally 50 yards to the parking lot.  ok in the parking lot, but when i pulled back into my driveway, the idle went down and i stalled.  started right back up, but the idle was obviously lower, down to 500.  had to do a 50 point turn to get her back into the garage past my other cars, stalled every time i stopped. idle is way lower now.  i did let it warm up before i drove it.  

it was nice to at least get her on the road after so many years.  though i was worried the whole time and it was only 50 yards!
Re: rebuilt carb, whistling sound and idling high and small pops/backf (17/25)
 11/8/17 3:17pm
C3RACER
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Lexington, NC - USA

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1974 Stingray. Street Scoop. Lots of new parts and working on getting it painted.


Joined: 9/27/2017
Posts: 17

Have you set your timing? Sounds like it may be retarded a bit. 

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1974 Stingray
Re: rebuilt carb, whistling sound and idling high and small pops/backf (18/25)
 11/9/17 8:59am
Target30
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1973 350 T-tops


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Posts: 31

forgive me, for this may be a really stupid question/comment...would i need to set it after rebuilding a carb?  it was running fine before all this crap went down(fuel line rotten, then pump went bad, then rebuilt carb).  i did take the distributor cap off once to check the position of the points, but it wen back on at the exact same place.
Re: rebuilt carb, whistling sound and idling high and small pops/backf (19/25)
 11/9/17 10:00am
C3RACER
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Lexington, NC - USA

Vette(s):
1974 Stingray. Street Scoop. Lots of new parts and working on getting it painted.


Joined: 9/27/2017
Posts: 17

Few different things. 
1. You always want to verify the three things that make a motor run: Fire,Fuel & Air
2. Timing can need to be readjusted after a carb rebuild, it mat have been set to over or under compensate for a carbs poor performance.
3. If the car ran good before what was the need to rebuild the carb? 
4. If very well could be the carb not set up properly. Do you have anyone that is in your neck of the woods that knows anything about old school motors if so it may be a huge benefit for you to ask.
5. Recheck everything on the rebuild. I have had new power valves in the carb be bad.
 Here is a PDF that might help you,

I will help you all I can from here.

Good Luck


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1974 Stingray
Re: rebuilt carb, whistling sound and idling high and small pops/backf (20/25)
 11/9/17 11:29am
F4Gary
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Grapevine, TX - USA

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1972 LT-1 convertible with factory air.


Joined: 8/26/2006
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You may have plugged a vacuum leak with that screw you put on the carb.  If that is the case, then you will need to recheck your timing.
On a side note, you may be using ported vacuum instead of manifold vacuum.  I've switched to manifold vacuum and have my LT-1 timed at 16* BTDC.


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Re: rebuilt carb, whistling sound and idling high and small pops/backf (21/25)
 11/9/17 2:18pm
Target30
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Vette(s):
1973 350 T-tops


Joined: 10/16/2017
Posts: 31

Thanks guys,

2. i can understand that, worth a check.
3. the fuel line rotted, i repaired it, then the fuel pump went out, replaced it(twice, first new one was DOA), then carb got gunked up, so i had to rebuild it.
4. i really do believe this to be the case.  i've been looking for someone around here.  otherwise, learning all i can while the search continues.
5.  i've read about bad power valves, even new.  it def would be my luck at this point!  haha!

Gary, i took the screw out.  the new gasket i put on after the rebuild caused the leak.  took the new gasket off, because the riser has a rubber gasket, and everything was fine after.  i've apparently never used that vaccuum port for anything before.  as it is now back to like it was.  i'm not sure what vacuum i'm using.  i can figure it out pretty quick though.
Re: rebuilt carb, whistling sound and idling high and small pops/backf (22/25)
 11/10/17 2:09pm
Target30
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1973 350 T-tops


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been busy, and now its getting cold. 29 today and 13 tonight...  anyhow, i started her up last night, she idled ack at 800 petty nice, couple of revs, still good.  i turned the idle mixture screws, nothing  they are completely closed and doesnt seem to have any effect.  so i gotta pull the carb apart again right?  also notice the secondaries dripping, and (forgive the stupid name) silver thing on top of the carb that shoots the fuel when you rev it, only shoots out of 1 side.  i had pulled it and cleaned it out and it was clean on both sides.  maybe got some other gunk in the carb?
Re: rebuilt carb, whistling sound and idling high and small pops/backf (23/25)
 11/16/17 9:59am
C3RACER
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Lexington, NC - USA

Vette(s):
1974 Stingray. Street Scoop. Lots of new parts and working on getting it painted.


Joined: 9/27/2017
Posts: 17

Just wanted to follow-up and see how it was going?

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1974 Stingray
Re: rebuilt carb, whistling sound and idling high and small pops/backf (24/25)
 11/20/17 4:25pm
Target30
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1973 350 T-tops


Joined: 10/16/2017
Posts: 31

thanks for checking back in.  i havent done much with it for a week or so.  been researching and i seems that since the idle screws seem to do nothing, or very little, i may have to pull the carb apart again...it hasnt gotten above 40 here and below freezing at night.  my garage is detached and not heated, so it may be a while before i pull a heater out and try again.  im busy gettting the kids ice rink set up and making sure the house is ready for winter!
Re: rebuilt carb, whistling sound and idling high and small pops/backf (25/25)
 11/27/17 1:06pm
nosal1
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Dunedin, FL - USA

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1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.


Joined: 3/21/2006
Posts: 257

    Here are 2 pictures attached of the rubber boot that I found on accelerator pump in a Q-Jet Carb of mine.
 
I had Ron at Carb shop take apart the BBC carb to determine why it,while connected up to fuel line and fuel pump, flow out of the center of carb and out the accelerator pump area.
 
Ron took apart carb and found a few internal parts corroded and replaced the blue part is part of accelerator along with cleaning out bits and pieces of rubber etc. in float and needle and seats.
 
This carb had about 3 weeks of running on my '72 truck and then took off of truck and in storage..
 
These corroded parts and deteriorated rubber is a results of the ETHANOL gas we are subjected to by the Government.As the fuel sits in the carb,it eats at the rubber internally and corrodes metal parts etc.
 
As long as you use the vehicle daily,you should not too much of a problem...
 
Thanks Congress!!!
Unfortunately I did not drain and rinse with mineral spirits before storing,shame on me..




 
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