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Thread: Vacuum leaks

  1. #31
    Member dougelam's Avatar
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    Hey Antz, what is your carb number?
    Can you take some pics of the top of your engine. One from each side, some of us will be able to see something that might not be right.

    Also you will need the thexton 370 Guage to adjust your carb properly.

    Do you have access to a fluke multi-meter?
    It's a must when diagnosing C3 systems unless you have an oscilloscope laying around

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    2002 W/Borla Exhaust

  2. #32
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    what is your carb number?

    Carb most likely the original. The number and date code match the engine block

    carb number: 17081217


    you will need the thexton 370 Guage to adjust your carb properly.

    I do have this.

    Do you have access to a fluke multi-meter?

    I have a 336 clamp meter, a 233 multi-meter (both fluke). also have a Brymen 869s (similar to a fluke 89) And a cheap meter for RPM, and Dwell

    Now the photo's
    20160424_161539-jpg20160424_161524-jpg20160424_161451-jpg

    Ignore the open vacuum port on the carb, it normally goes to the vac motors on the air cleaner.
    Any help anyone can give would be great. This is the first carburetted car I've owned; so any ideas anyone has would be very helpful.

  3. #33
    Moderator bill81vette's Avatar
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    that is the correct carb for your vette...
    Bill and Gail...save the wave
    NCRS member 42415
    1981 St.Louis car #2735
    all matching numbers

    born Sept 18,1980
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    Without Trucks......
    You would be Hungry,Homeless and Naked!!!!!!



  4. #34
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    OK the first thing that I see is the original coolant temperature sensor, they were very unreliable. You need to update it with
    GM Closed Element CLT / IAT Sensor with Pigtail
    It comes with a new connector also, the old ones caused a couple of problems.

    Second please tell me that those are not ignition wires zip tied to your wire harness!

    Now, when spraying your wd40/carb cleaner around to find vacuum leaks it is sealing the leak so unmetered air isn't going into your intake hence it smooths out the idle. Spraying into your carb means nothing (at this point in the repair). As said before you need to isolate all the external devices that are controlled by a vacuum hose which in your case is the headlight doors, canister purge and thermac (air cleaner) if used. You Do need to have the correct PCV VALVE, a CV774C AC DELCO, not what ever the parts store wants to sell you. It is a calibrated vacuum leak and the wrong one will either allow to much air through making it difficult to correct with your MC solenoid or not enough and then it allows to much pressure to build up in your crankcase which unturn causes oil leaks.

    I do not understand why Peer81 would use the EGR port for a vacuum check, it is ported (only has vacuum when the primaries are open, not at idle) you want to check Manifold vacuum at idle at the Manifold!

    As for base ignition timing that was a good find with your TDC mark!
    You didn't say if you by passed your EST (Electronic Spark Timing) when setting it
    Check your ignition module, AGAIN if it's an aftermarket one it WILL NOT have the proper spark advance built into it. Less power or spark knock will occur.

    Check your PROM (Programable Read Only Memory) some are better than others, you don't want one with California emissions!

    And PLEASE post before or during your carb re-calibration, there is a lot more to it than what is printed on the rebuild kits instructions.

    Provided that there isn't any mechanical problems with your engine I know we will have you up and running soon

    Hang in there,
    Doug

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    2002 W/Borla Exhaust

  5. #35
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    OK the first thing that I see is the original coolant temperature sensor, they were very unreliable. You need to update it with
    GM Closed Element CLT / IAT Sensor with Pigtail
    It comes with a new connector also, the old ones caused a couple of problems.
    Good to know. I will order one.

    Second please tell me that those are not ignition wires zip tied to your wire harness!
    When I replaced them i simply put them back where they were. Thinking about it having, 20000v+ leads next to the 12V (and less) harness doesn't seem so bright. Have new retaining clips coming so I can re-route them the correct way. but have moved them away temporarily.

    As for base ignition timing that was a good find with your TDC mark!
    You didn't say if you by passed your EST (Electronic Spark Timing) when setting it
    Check your ignition module, AGAIN if it's an aftermarket one it WILL NOT have the proper spark advance built into it. Less power or spark knock will occur.
    I assume you mean by-passed it by unplugging the 4 pin connector on the distributor (which I did)
    Having a little trouble working out if the ignition module is correct or not. Its GM (with a yellow dot), with 466 on the case as well as 617*0M28 . Can't tell if there is ment to be a digit where i put the *. Any ideas if this is the correct on?

    Check your PROM (Programable Read Only Memory) some are better than others, you don't want one with California emissions!
    Prom Number is 6084FN. (81 4spd fed emisions 1st design) So this seems fine.

    You Do need to have the correct PCV VALVE, a CV774C AC DELCO
    This is what i have, but i'm not sure on its age. I'll order a new one just to be sure.

  6. #36
    Member dougelam's Avatar
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    The factory ignition modules came with a yellow dot on it so to match the pole piece and coil which have yellow and white wires on them to designate a clockwise rotation.

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  7. #37
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    You know what, I should have stated yellow and red. Sorry I've been out of automotive for 9 years so some things are a little sketchy.

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  8. #38
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    Ant are you planning your carb rebuild anytime soon?
    Living in Michigan, working for a Chevrolet dealership I was very lucky to be close to Warren.
    There I was trained by GM DRC (Dealer Repair Center) technicians on CCC Control systems, that is a lost art and I am looking forward to helping you through it. When your done you will be really happy with the results.

    Your 17081217 carb is not a fixed idle air bleed design which means it works very well with most changes you make☺

    A heads up, get a new TPS (Throttle Position Sensor) with your Carb kit

    Doug

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    Quote Originally Posted by dougelam View Post
    Ant are you planning your carb rebuild anytime soon?
    Living in Michigan, working for a Chevrolet dealership I was very lucky to be close to Warren.
    There I was trained by GM DRC (Dealer Repair Center) technicians on CCC Control systems, that is a lost art and I am looking forward to helping you through it. When your done you will be really happy with the results.

    Your 17081217 carb is not a fixed idle air bleed design which means it works very well with most changes you make☺

    A heads up, get a new TPS (Throttle Position Sensor) with your Carb kit

    Doug

    Sent from my SM-T530NU using Tapatalk
    I have a rebuild kit (including a new tps). I don't have any plans to rebuild it yet though. If you think I should then I will.

  10. #40
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    Once you think that all your vacuum leaks are corrected then that will be the icing on the cake!
    Can you take a pic of your kit and the tools that you have related to the repair.


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    2002 W/Borla Exhaust

  11. #41
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    Quote Originally Posted by dougelam View Post
    Once you think that all your vacuum leaks are corrected then that will be the icing on the cake!
    Can you take a pic of your kit and the tools that you have related to the repair.


    Sent from my SM-T530NU using Tapatalk
    I'll upload photos when i get home.
    But have the thexton 370 and 380 tools haven't found the angle guage yet (372?) Would this be a good substitute for it? Help Parts Carburetor Choke Angle Gauge GM 2 4 Barrel Carburetors | eBay

  12. #42
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    It should work

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    This is the rebuild kit I have.20160426_182846-jpg
    And these are the specific carb tools20160426_174325_001-jpg
    Plus i have the choke angle gauge on it's way. It and the other bits and pieces should arrive early - mid May.

    As for vacuum leaks, I think I only have one very small one left somewhere in the cabin vent controls. (Although it doesn't seem to make any difference if I block this off or not.)

  14. #44
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    Even a new MC solenoid, nice
    How about a hand held vacuum pump?
    The carb feet are nice to use but 4 bolts will work OK, that and a little patience

    Keep us informed

    Doug

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  15. #45
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    Yes do have a hand held vacuum pump. It's a must when working on these cars.
    Don't carb feet, I was going to make something at work, but four bolts sounds a lot easier.

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