C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette
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Frustrated...help please.

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Old Jan 3, 2012 | 03:41 PM
  #21  
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Sounds like you may have a big vacumn leak. If car has power brakes, check your brake booster. Just pull valve out of booster hand hold finger over it while engine running. If it smooths out, you have a bad brake booster.
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Old Jan 3, 2012 | 04:15 PM
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Is the backfire coming from the carburetor or is it "after fire" in the exhaust?
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Old Jan 3, 2012 | 04:18 PM
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Originally Posted by birdsmith
Two things...you didn't mention where you're holding the gas pedal while cranking; and your choke may be sticking. It sounds to me that everything that might be causing a problem has already been looked at and/or corrected. Give it a couple squirts of gas before you crank it then hold the pedal to the floor and see if it tries to start. If that does nothing pull a valve cover and start comparing rocker movement...hate to say it but all that time sitting may have caused a cam lobe or twelve to go flat very quickly after a dry startup...it ran (kinda) for a few minutes while it was grinding the lobes off the cam. If that's what you find, STOP. You'll just be pumping metal chips through your motor. best of luck; hopefully it's just an easily correctable carb issue and not the latter...
Birdsmith- Good news! I pulled the valve covers and no signs of any metal shavings, did find a couple of loose rocker arms and tightened them up a little. Bad news is it still won't start, found the bottom gasket saturated so will pull the carb and replace, hopefully the base isn't warped if so it's off to Summitt for a replacement. I appreciate your help!
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Old Jan 3, 2012 | 04:20 PM
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Originally Posted by Les
If you can bolt on a carb that you know works properly you can definitively determine whether it's the carb or not. After everything else that you've done that would be my next step.
Les- I don't have another carb to try, would be a great idea though. Did find the bottom gasket saturated, will pull it tomorrow and replace as well as check the carb base to see if it is warped. I've already got Summitt on my speed dial just in case...
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Old Jan 3, 2012 | 04:22 PM
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Originally Posted by brrujo
Sounds like you may have a big vacumn leak. If car has power brakes, check your brake booster. Just pull valve out of booster hand hold finger over it while engine running. If it smooths out, you have a bad brake booster.
It's worth a shot, as soon as I can get it started....
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Old Jan 3, 2012 | 04:24 PM
  #26  
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Originally Posted by Roco71
Is the backfire coming from the carburetor or is it "after fire" in the exhaust?
Backfiring out of the exhaust, now won't even start. Going to replace the bottom gasket on the carb found it saturated with gas so it is more than likely leaking, will check carb base as well to see if it is warped. Thanks!
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Old Jan 3, 2012 | 04:31 PM
  #27  
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Originally Posted by MidTex73
Birdsmith- Good news! I pulled the valve covers and no signs of any metal shavings, did find a couple of loose rocker arms and tightened them up a little. Bad news is it still won't start, found the bottom gasket saturated so will pull the carb and replace, hopefully the base isn't warped if so it's off to Summitt for a replacement. I appreciate your help!
Simply tightening loose rocker arms won't necessarily fix the problem...the fact that they were loose at all would indicate a cam wear problem, i.e., material has worn off of the cam making the lash adjustment disappear. Were the loose rockers' cam lobes on their respective base circles? And if you did wipe the cam I'd be surprised to find shavings under the valve covers...they would generally be laying in the pan or have gotten sucked into the oil filter. You might want to remove that filter and cut it open just to see what's inside...
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Old Jan 3, 2012 | 04:39 PM
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Originally Posted by birdsmith
Simply tightening loose rocker arms won't necessarily fix the problem...the fact that they were loose at all would indicate a cam wear problem, i.e., material has worn off of the cam making the lash adjustment disappear. Were the loose rockers' cam lobes on their respective base circles? And if you did wipe the cam I'd be surprised to find shavings under the valve covers...they would generally be laying in the pan or have gotten sucked into the oil filter. You might want to remove that filter and cut it open just to see what's inside...
By loose, I mean minute side to side play (very minute) no up and down loosening. I'm planning on changing the oil in the morning just as a precaution and will check the filter then. Thanks again!
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Old Jan 3, 2012 | 07:53 PM
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Looks like the new coil I bought maybe a dud. checked resistance from post to post 1.7, then checked the post to tap was 7.71kohm? What I have read it should be 11 to 13.49 if functioning properly. Is this correct?
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Old Jan 3, 2012 | 08:50 PM
  #30  
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Originally Posted by MidTex73
By loose, I mean minute side to side play (very minute) no up and down loosening. I'm planning on changing the oil in the morning just as a precaution and will check the filter then. Thanks again!
I don't know your level of expertise so please don't be insulted by my question. Did you rotate the motor so that the lifters were on the back side of the cam for each valve before you adjusted the rocker arms?
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Old Jan 3, 2012 | 09:09 PM
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Originally Posted by Les
I don't know your level of expertise so please don't be insulted by my question. Did you rotate the motor so that the lifters were on the back side of the cam for each valve before you adjusted the rocker arms?
Yes sir.
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Old Jan 3, 2012 | 10:13 PM
  #32  
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Originally Posted by Les
Based on the possible flooding description my first thought was float prolems and/or sticky needle & seat. There's a lot of info if you do a Google search on "Qjet needle and seat". Here's just one link that covers that and a few other possibilities. Good luck.
http://www.jalopyjournal.com/forum/s...d.php?t=202866


a small trick with the carb removed is to blow through the fuel inlet with the carb upside down and if you can, the needle and seat is stuck open...if you cant, the carb could be used
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Old Jan 4, 2012 | 08:32 AM
  #33  
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Did it smoke when you parked it a year ago? You made adjustments to stop it from smoking, how much adjustment? What adjustment?
Borrow a carb from someone who has a running vehicle, try ir inplace of your's. You had it rebuilt for a reason. Seems like the issue has been carb for a while.
I'd try the exchange to stop spending cash.
What was wrong with the carb last year that required the rebuild?
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Old Jan 4, 2012 | 09:51 AM
  #34  
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Originally Posted by Indiancreek
Did it smoke when you parked it a year ago? You made adjustments to stop it from smoking, how much adjustment? What adjustment?
Borrow a carb from someone who has a running vehicle, try ir inplace of your's. You had it rebuilt for a reason. Seems like the issue has been carb for a while.
I'd try the exchange to stop spending cash.
What was wrong with the carb last year that required the rebuild?
Air/Fuel was 4 rounds out went back to the recommended 1.5 rounds each. Had it rebuilt "probably bubba'd" by a local mechanic that supposedly specialized in Qjets. Don't have a spare carb or one I can borrow. Just ordered a new Holley hopefully this will help. On the bright side, I did get it started, ended up being the wire from the coil to the distributor, last thing I checked..... Air/fuel adjustments don't seem to change anything on this carb so I put it back where each is 1.5 rounds out.
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Old Jan 4, 2012 | 09:52 AM
  #35  
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Originally Posted by Ironcross


a small trick with the carb removed is to blow through the fuel inlet with the carb upside down and if you can, the needle and seat is stuck open...if you cant, the carb could be used
Ordered a new Holley this morning. Not a big Qjet fan anyway. Thanks!
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Old Jan 4, 2012 | 08:27 PM
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Originally Posted by MidTex73
Yes sir.
OK, great. Sorry for asking but I figure it's better than finding out too late that you've hurt your motor. Good luck with the new carb. I've never been a huge Q-jet fan either.
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