91 350 TBI Engine maintenance.

Discussion in 'Engine Performance + Maintenance' started by Ds9Defiant1701, Apr 22, 2021.

  1. Nad_Yvalhosert

    Nad_Yvalhosert I'm Awesome

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    Indexing the plugs puts the plug gap directly between the intake and exhaust valves where the opening "throws" the spark into the dead center of the combustion chamber.
     
  2. Nad_Yvalhosert

    Nad_Yvalhosert I'm Awesome

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    I came across a website for 3rd Gen F-bodies that listed many mods for the TBIs. Most would cross over to our trucks... such as cleanliness, proper timing, cold air in and low restriction of exhaust out.
    One that stuck in my brain was adjusting the fuel pressure regulator to add just a couple PSI for better fuel atomization, then adding 2 additional degrees of ignition timing.
    Thing is, the gains were 3 hp. 3!
    Can your calibrated SOTP dyno tell the difference between a 210 horse engine and a 213 horse engine?
    In my mind, NO. Just leave it alone and drive it.
     
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  3. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    Isn't that what slanted plugs are for, pointing them more towards the exhaust valve?
    Trick Flow Chamber.JPG
     
  4. Nad_Yvalhosert

    Nad_Yvalhosert I'm Awesome

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    No, you need to know where in 360° that the ground electrode is when the plug is tight. Specifically if the ground strap is between the center electrode and the intake valve, forcing the flame to go around.
    With the head off, like the picture, one could install and see where the plug is when tight.
    With the head on the engine, you would need to make a mark on the plug somewhere and test fit multiple plugs into multiple cylinders multiple times.
    Again, you're grasping at straws trying this mod. You're only able to attain a quarter horsepower increase at best...
     
    Last edited: Apr 30, 2021
  5. Schurkey

    Schurkey I'm Awesome

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    Ancient history. Autolite hasn't been Honeywell for ten years. Autolite has been passed from one owner to another like the town pump. They're now owned by First Brands Group (Fram filters, Luberfiner filters, Champion Laboratoies Filters, Trico and Anco wiper blades, Raybestos, Carter fuel and water pumps.)

    https://www.autolite.com/news/post/...)-and-champion-laboratories-inc.-(champ-labs)

    https://en.wikipedia.org/wiki/Autolite
     
    Last edited: Apr 30, 2021
  6. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    That seems to be a waste of time, IMHO. You can just throw e3 plugs in and accomplish the same thing. I can't remember which Engine Masters episode it was but, IIRC they gained 5 HP+ over conventional plugs.
     
  7. Erik the Awful

    Erik the Awful Supporting Member

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    I don't remember that, and I can't find the episode. I'm not a fan of any funky plug that makes silly promises. Back in the day, my RX-7's NGK spark plugs had four-prong grounds. They didn't make a "hotter spark", and the spark didn't jump between different electrodes. What the four ground straps maybe did was allow the plugs to last longer. Whichever strap was a hair closer to the electrode got the spark jump, and as the electrode wore away on that side, it would start sparking from a different strap. With an MSD 6A, my RX-7s plug electrodes would get worn down to nubs and still fire. The old "split fire" plugs were the same way. The spark only ever jumped from one side, and if that side of the electrode wore down, it would start sparking from the other side. When E3 plugs first came out, they had a groove in the underside of the ground strap, and they advertised that same garbage that their plug would "make multiple sparks".

    I also don't think indexing plugs really makes much difference. It doesn't "throw the spark" anywhere. The spark will always follow the path of least resistance between the electrode and ground. There is some evidence that with a low compression, straight plug motor, indexing helps, but I think your horsepower gain would be within the margin of error on a dyno. In PlayingWithTBI's picture, the top of the ground strap will always be between the electrode and the intake valve, and as the air/fuel mixture has been compressed, it's all right there when the ignition strikes. Is the ground strap going to make a measureable difference in how the flame wave propogates through the chamber?
     
  8. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    I seem to remember it was towards the end of the show about some other comparison. I was really surprised that they actually gave them a gain in HP since I was always of the same opinion that these new funky things don't do much of anything. I didn't run out and buy any though, I still have NGK plugs in mine.:Big Laugh:
     
  9. bhopthewelder

    bhopthewelder Newbie

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    Pointing slightly towards the exhaust valves. Better combustion and more complete burn.
     
  10. bhopthewelder

    bhopthewelder Newbie

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    They sale indexing kits. It's easy as pie.
     

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