Plug Gap on 4.9L??? (also Bosch Injector Question)
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HT4100 4.1, 4.5, 4.9 Discussion, Plug Gap on 4.9L??? (also Bosch Injector Question) in Cadillac Engine Technical Discussion; Hello, I am still fighting my stumble issue. Can anybody tell me what plug gap should be on a 1991 ...
  1. #1
    cjhudson87 is offline Cadillac Owners Member
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    Plug Gap on 4.9L??? (also Bosch Injector Question)

    Hello,

    I am still fighting my stumble issue. Can anybody tell me what plug gap should be on a 1991 4.9L Seville? Mine are at like .060"

    Also, I saw a post about Bosch 19lb injectors from 5.0 Mustangs being a hot upgrade for the 4.9L motors. I happen to have a known good set lying around from my 1988 Mustang and was thinking about throwing them in too. Will these work on my 1991 Seville?

    Thanks!

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    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    The gup should be 0.060". As for injectors, I am waiting for some input to.

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    cjhudson87 is offline Cadillac Owners Member
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    0.060"?

    I've never had a vehicle that was supposed to have that huge a plug gap.

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    behind-bars is offline Cadillac Owners Connoisseur
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    It says the gap on the emissions sticker under the hood, .06 sounds right from memory. The plugs I got (delco rapid fire) were pregapped.

  6. #5
    pompste is offline Cadillac Owners Connoisseur
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    Quote Originally Posted by cjhudson87 View Post
    0.060"?

    I've never had a vehicle that was supposed to have that huge a plug gap.
    The .060 gap is correct.I had my plugs changed 2 weeks ago--ac/delco platinum tipped on my 4.9 litre.They came pre-gapped but i checked them myself anyway---they were correct.

  7. #6
    NickySantoro is offline Cadillac Owners Fanatic
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    Tah Dah!

    Manual says......... .060"

    BTW, always check the gap. It will take two minutes, if that, to check all eight. Mostly they are OK out of the box. Over the years I've seen far too many that were not for whatever reason. Personally, I'm unwilling to run the risk of installing an incorrectly gapped plug on #4 or #6 and having to battle those two twice.

  8. #7
    ChadTanner is offline Cadillac Owners Member
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    I done alot of research and testing on these injectors.The 4.9 and the stock mustang injector [when flow tested] flowed about the same, at 40psi they both flowed in the 20ish range.Thats far more than this engine could ever use.I had a local diesel shop do the flow testing,The owner also built and raced 5.0 mustangs.He showed me the difference in the spray patterens between the two injectors.The caddy injector has a much better spray patteren than the mustang.He went as far to say"the caddy injector would be an upgrade for a stock 5.0"

  9. #8
    1badcad is offline Cadillac Owners Member
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    I just put BOSCH injectors in my 4.9 today,WOW what a difference.No more rough idle and hesitation on acceleration."CHANGE THEM AND NEVER LOOK BACK"

  10. #9
    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    Quote Originally Posted by 1badcad View Post
    I just put BOSCH injectors in my 4.9 today,WOW what a difference.No more rough idle and hesitation on acceleration."CHANGE THEM AND NEVER LOOK BACK"
    Great! Is it possible to replace injectors without removing PS pump? Where did you get the injectirs? New or reman.?

  11. #10
    4.9fiero is offline Cadillac Owners Member
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    I got mine from Jegs www.jegs.com cheaper than dealer replacements. As for rebuilt, don't bother, these can't be taken apart and "rebuilt", they can only be cleaned. http://www.cruzinperformance.com/ will clean and flow check them for .$16.00 per injector + actual return shipping., I've used them for 3 sets and when I sent him my 4.9's he emailed me back with the news that one was plugged completely, the rest were so far out of spec that he wouldn't recommend continuing. Pointed me in the direction of Bosch and charged me $12 for his trouble. They don't sell injectors so he had nothing to gain, just an honest business.

  12. #11
    HUF's Avatar
    HUF
    HUF is offline Cadillac Owners Connoisseur
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    Re: Plug Gap on 4.9L??? (also Bosch Injector Question)

    Quote Originally Posted by 4.9fiero View Post
    I got mine from Jegs www.jegs.com cheaper than dealer replacements. As for rebuilt, don't bother, these can't be taken apart and "rebuilt", they can only be cleaned. http://www.cruzinperformance.com/ will clean and flow check them for .$16.00 per injector + actual return shipping., I've used them for 3 sets and when I sent him my 4.9's he emailed me back with the news that one was plugged completely, the rest were so far out of spec that he wouldn't recommend continuing. Pointed me in the direction of Bosch and charged me $12 for his trouble. They don't sell injectors so he had nothing to gain, just an honest business.
    4.9fiero,
    Thank you for the info. I should take care of my injectors ASAP too!

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