Results 1 to 9 of 9

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
    Location
    Ct
    Posts
    479

    Default

    Retarded ignition timing can also cause the EGT run hot.

  3. #3

    Default

    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
    Location
    Connecticut
    Posts
    27,080

    Default

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

  5. #5

    Default

    @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

    Default

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

  7. #7

    Default

    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
    Location
    Brisbane, Australia
    Posts
    1,977

    Default

    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

    Default

    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!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us