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Thread: Sick L98
          
   
   

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  1. #16
    34_40's Avatar
    34_40 is offline CHR Member Visit my Photo Gallery
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    I'd agree with Mr. Spears, easiest things to check are the grounds, they are crucial to complete the circuit and often overlooked.

    You can use a jumper cable right from the battery (-) to a clean metal spot on the motor and see if the motor runs without interruption. Quick and easy way to test.

  2. #17
    mr-natural is offline CHR Member Visit my Photo Gallery
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    More data points

     



    Well, here's a few more data points. When I said the engine runs after reconnecting the EST bypass that was telling only a part of the story. Here's some more detail. With the EST bypass disconnected I set the timing to about 12° BTDC and the engine would start nicely and run good for 5-10 second and die. While watching the timing mark it is clear that the spark stopped right before the engine quit. So I reconnect the EST bypass and now the engine will stay running if you feather the throttle BUT it is backfiring through the exhaust and the timing is now off scale at about 16° ATDC. All components inside the distributor are new including coil and cap. Disconnecting the EST module does not change a thing. I've gone through all the grounds and they are good. New computer - same same. Should I rip out the damn tuned port and put a carb on?

  3. #18
    mr-natural is offline CHR Member Visit my Photo Gallery
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    Well, here's a few more data points. When I said the engine runs after reconnecting the EST bypass that was telling only a part of the story. Here's some more detail. With the EST bypass disconnected I set the timing to about 12° BTDC and the engine would start nicely and run good for 5-10 second and die. While watching the timing mark it is clear that the spark stopped right before the engine quit. So I reconnect the EST bypass and now the engine will stay running if you feather the throttle BUT it is backfiring through the exhaust and the timing is now off scale at about 16° ATDC. All components inside the distributor are new including coil and cap. Disconnecting the EST module does not change a thing. I've gone through all the grounds and they are good. New computer - same same. Should I rip out the damn tuned port and put a carb on?

  4. #19
    rspears's Avatar
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    Mr-Natural, everyone else may recognize "EST" but it's Greek to me. I have absolutely no idea what you mean by "EST Bypass". If you use an acronym it would really help if you'd define it at least once. IMO a good EFI system is an improvement on a carb, but I'd say that for me it makes sense to go with one of the new aftermarket, self learning systems as opposed to trying to band aid an OEM system.

    I wish you the best figuring out your system, and truly hope that you get it sorted out.
    Last edited by rspears; 03-08-2021 at 05:44 AM.
    Roger
    Enjoy the little things in life, and you may look back one day and realize that they were really the BIG things.

  5. #20
    mr-natural is offline CHR Member Visit my Photo Gallery
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    The latest!!!!!! I gave up and for the first time in the 56 years I've owned this Corvette I brought it into a "guy" who knows L98s. Within the first 5 minutes he determined I had a vacuum leak - turns out my factory runners were warped. He figures it was about a 0.015" gap. He installed a pair of used BBK runners - part of the problem solved. Next was the jumping timing issue - just like I described earlier, one minute stable then all over the place. Believing me that I had totally gone through the distributor he stuck in another used unit - problem solved - well mostly. After the new used distributor the alternator started putting out 16 volts. He stuck in a new rebuilt NAPA alternator as the one that failed was still under warrantee. I picked the car up and while driving home the ammeter was all over the place from discharge to overcharge. Since this "guy" is 38 miles from home and my ride had already left I continued on home. Pulled the alternator and got another rebuild from NAPA. Stuck it in and it too is putting out too much voltage pegging the ammeter - 15.1 volts. Went back and got another one - this one has the same issue that the one I drove home with but not nearly as bad. Ammeter jumping around but not too ridiculous. Ordered a 1 wire regulator for my 10SI alternator and I'll replace that soon. OH, almost forgot, still backfiring through the intake when cold but goes away when warmed up but other than that it runs strong.
    Last edited by mr-natural; 04-30-2021 at 10:02 AM.

  6. #21
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    Well. I guess that's some progress. Better than zero!
    I wonder if the overvoltage / overcurrent is cooking your electronics?

    And EVERY time I had an Alternator not regulate itself, there was a failed GROUND involved.
    Last edited by 34_40; 04-30-2021 at 10:29 AM. Reason: just because
    rspears, 40FordDeluxe and 36 sedan like this.

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