Keith Black Pistons

Discussion in 'Engine Topic' started by nova75mike, Mar 11, 2010.

  1. nova75mike

    nova75mike Veteran Member

    Mar 20, 2008
    Etters, PA
    Has anyone here had a bad experience with them?? I ran a set years ago in a 355 that I raced. They were 11:1 pop-ups with the 1/16 ring pack. I ran them for 4 years with no issues, then sold the motor to a guy who ran them for another few issues. Lately I've been reading online, and hearing from other racers that KB pistons are JUNK!! What happened? Did they change the design, machining?? Anybody have any issues?
  2. efh

    efh Member

    Mar 10, 2010
    guelph ontario
    Far from my favorite but I've never had any problems when people want to use them , if they are hyperuetics you have to follow their ring gap specs or you'll have problems
  3. Greg Mc

    Greg Mc Veteran Member

    Mar 18, 1999
    Hernando, MS
    I think most of the complaints are about their Hyper pistons. Ring gap has to be set a little wide and exactly per manufacturer specs or may have problems. I am using KB forged in a BB I am building and don't expect any issues.
  4. Damon

    Damon Veteran Member

    Nov 16, 2000
    Philly area
    They (the hypereutectic ones) don't hold up well to the kind of vicious detonation that can happen in a nitroused or boosted application, but I've run quite a few sets of them in many motors successfully. I've never broken them except while working my way up a fairly steep learning curve with my last few supercharged engines.

    There's nothing wrong with KBs, it's just that hypereutectic pistons aren't what you want from any manufacturer in a power-adder application.

    KB has an excellent article on their website about hypers vs. forged that your should read so you understand WHY.

    The short version is: it has almost nothing to do with the strength of the piston. Hypers can be every bit as strong as forged. The difference has more to do with how they manage the heat of combustion. Forged units pull heat out of the chamber/piston face much faster than hypers. Hypers keep it "bottled up" above the piston. In heavy detonation when combustion temps spike wildly the heat doesn't get carried down the piston body away from the top ring as quickly. Causes the top ring to overheat, expand, and close the gap down to nothing. When the top ring gap hits zero the ring locks in the bore and on the next down-stoke it rips chunks of the ringland off above the top ring. Those chunks then do very bad things to the motor very quickly (ka-boom!).

    When you've successfully blown one up, it looks like this if you got away easy:


    And it looks like this when you really grenade one:

  5. 71Z28

    71Z28 Member

    Feb 13, 2010
    Greensboro, MD
    No problems here KB 13.5:1 forged
  6. NYH1

    NYH1 Veteran Member

    Feb 27, 2010
    Central New Yorkistan
    My Scat otating assembly (385 stroker) came with Keith Black FHR series 19.6cc dished forged pistons. I have a book by David Vizard and he says he uses Keith Black Pistons in 1 out of every 3 engine builds he does. He says even their claimer series pistons are of good quality.

    I'm glad I bought his book. He has a lot of good information it besides just pistons. Honestly, if I didn't go with the Scat kit that came with the KB FHR series forged pistons I wouldn't have been able to afford forged pistons at all.

    That being said, I'm not building a race motor. Just trying to get an honest 350 HP and 425/450 FT. LBS. of torque. I might add a 75 to 100 horse hitter down the road. From everything I've read and have been told, they should work really well with my set up.
  7. nova75mike

    nova75mike Veteran Member

    Mar 20, 2008
    Etters, PA
    I know they need a special top ring gap from when I put mine together. I have a buddy that lifted all 8 top ring lands off his popups in a 383. Made a SERIOUS mess at 6000 rpm's at 1000 feet. Now I'm helping a friend put a 400 horse 350 together for a street car on a budget. You cant beat a set of these pistons at $190.00 in my opinion. I'm starting to think that all the negative I've heard about them is from not paying attention to the top ring gap.
  8. heavy duty

    heavy duty Veteran Member

    Sep 29, 2005
    Cactus Forest Arizona
    Detonation will damage any piston. forged or cast if allowed to continue. Its like hitting the piston with a hammer.
  9. CamaroMan79

    CamaroMan79 Veteran Member Lifetime Gold Member

    Jun 10, 2001
    Selah, WA
    I ran the KB Hypers on many motors including a 500+hp 406 without issue. I think all the issues you hear about are from ppl that didnt know what the hell they were doing with there engine.
  10. 74RAT

    74RAT Veteran Member

    Dec 28, 2003
    ft. stockton,tx,usa
    this right here^^ pretty much stems from the ring gap issue along with not pulling the recommended timing in combonation with trying to get away with not enough octane or too lean and onsetting detonation.

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