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Thread: Sniper EFI and exhaust gas temps.

  1. #1

    Default Sniper EFI and exhaust gas temps.

    Installed a Sniper EFI on our '72 Chevelle. While we had it down I had Jet Hot coat the headers and intake. After about an hour (of on & off time) running the car in my shop the coating on the headers began to burn off. With shipping it was almost $1000 to have the headers and intake coated. The car is running pretty well now and sorted out so I called Jet Hot about what their warranty covers. One of the first things they stated was that EFI cars tend to run lean to be safe and can easily exceed the 1250°F limit of the headers. Does this sound right? I don't have a heat temp gun and never checked the headers to see how warm they had gotten, but watching the AFR on the handheld it all looked normal and within specs. What do you think?

  2. #2
    Join Date
    May 2019


    Retarded ignition timing can also cause the EGT run hot.

  3. #3


    It's a 383 SBC and the timing is set at 32°F. Would this combination every see about 1250°F on the temps for exhaust gases? That seems crazy high to me.

  4. #4
    Join Date
    Dec 2009


    Buy an infrared thermometer gun and measure your header primary tubes. Also, ensure the ignition timing is synchronized with the ECU.

  5. #5


    @Tar Heel: They're yanking your chain. There's no reason for EFI exhaust systems to run hotter or colder than a carb. If the AFR and the timing is the same then both engines will run the same. My guess is that your timing curve is a bit retarded from what you think it is, so the exhaust got hot. You should be able to confirm that by using a timing light.

  6. #6


    Is your timing synced correctly? I have Jet Hot coated headers with no issues from the Sniper.

  7. #7


    That seems incredibly hot. I don't think my headers have ever gotten over 400°F, and yes, I've checked them with a thermal gun on numerous occasions over several years both with my old 305 TPI engine on nitrous, and with this 406 with a Sniper.

  8. #8
    Join Date
    Jan 2010
    Brisbane, Australia


    Quote Originally Posted by Tar Heel View Post
    The car is running pretty well now and sorted out so I called Jet Hot about what their warranty covers.
    Did you have troubles at the start, like difficulty starting, low power, etc?
    As other boys have stated, EGTs will be higher with retarded ignition timing. The combustion chamber does not know if it's fed from a carburetor or an injector. If the timing and AFR are correct, the EGTs should be normal.

    You may have pushed the coating too hard if anything was wrong in your first pulls.

    I would've run a few warming cycles first, to check everything was normal.

    Jet Hot 1250 is not as good as their 2500. Gary

  9. #9


    When we first put the EFI on, it was having trouble starting. We run a fairly large, solid roller and make pretty good HP. With no vacuum it took us a couple starts & idles to get things right. Maybe it did push the limits of the coating. Perhaps when I get a chance, now that it seems sorted out, I'll have them recoated after I check the temps with a thermal gun. Thanks for the replies!

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