Smallblock Pistons: 1 question.....KB's -or- Sealed Power(SpeedPro hypers)???

Discussion in 'Small Block Mopar Engine' started by V24x2, Nov 28, 2018.

  1. V24x2

    V24x2 Well-Known Member

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    Simple question like the title states...
    KB's -or- Sealed Power(SpeedPro hypers)??? for a smallblock street/race build. Thankyou.
     
  2. dartfreak75

    dartfreak75 Well-Known Member

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    I dont have an answer on which ones are better. It really depends on what your built Intel's. But I will say this Kbs are lighter and usually have a higher compression height. But the speed pros (so I have read) are stronger. And they are closer in weight to factory pistons in most instances. What are you building? 318 340 or 360?
     
  3. V24x2

    V24x2 Well-Known Member

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    Were building a street/strip 340 so i can introduce my kids into Dragracing.ive been into it for some time and i usually put forged pistons in my engines but im not looking for them to hop in a 11sec street machine, ya know? Just a healthy .500+/- cammed 340 with the obvious goodies, auto and maybe 4.10 or 4.30 gears. Thanks
     
    Last edited: Nov 28, 2018
  4. Garry in AZ

    Garry in AZ Building a 9 second Valiant FABO Gold Member

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    The brand is not as important as the type of piston you choose. Hypereutectic pistons are still cast pistons, and they will not tolerate the abuse that a forged piston will. They do run quieter at start up, and they have good wear characteristics, but if you plan on a high rpm motor, any sort of power adder, or if there is even a chance of detonation, I would use forged pistons.
    If the motor is basically a daily driver with just the occasional romp, you may be fine with the hypereutectics. Many OEM high performance motors come from the factory with hypereutectic pistons, and they are generally reliable until boost or nitrous is added. It should be noted however, that these modern high performance engines have computer controlled anti-knock systems to prevent accidental detonation, which break hypereutectic pistons really quick.
     
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    • thesiren74

      thesiren74 Well-Known Member

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      Speed pros are strong, been abusing them since 2012 in my old 360.
       
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      • Garry in AZ

        Garry in AZ Building a 9 second Valiant FABO Gold Member

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        Again, the brand does not dictate the strength... the type of piston does.
        Speed Pro, KB, Mahle, Diamond, Wiseco, Manley... all make both forged and hypereutectic pistons. In every brand, the forged style are the strongest.
        You shouldn't choose pistons by the brand name!
         
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        • V24x2

          V24x2 Well-Known Member

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          Thankyou Gary...so basically spending the extra $$$ for the KB name over SpeedPros, im just throwing my $$$ out the window. Its a budget build so that answer i approve of! Thankyou.
           
        • V24x2

          V24x2 Well-Known Member

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          ....and by the way, i do have a REV-LIMITER and i do plan on using it!
           
        • 318willrun

          318willrun Stomper 4x4... we kept energizer in business

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          11's, on pump gas? I would think stock pistons would be fine
           
        • nm9stheham

          nm9stheham Well-Known Member

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          Speed Pro's like the H116CP are hyper's like KB's. Icon's are forged. ICON FHR's are lower cost forged.

          I've raced a long time on both hypers and forged (rallying) with 14-15 psi boost so they can both last well. Forged MIGHT save you from a broken piston if you get into detonation versus a hyper.... but I say MIGHT. I've broken/melted ring lands out of some stout forged pistons when detonation reared its ugly head. For what the OP lists as a use, I would not be scared to go with a hyper.

          The KB's will require you to re-balance the crank as they are quite a bit lighter. The Speed Pro's are usually stock weight replacements. Most everything else will require a re-balance. (Unless you get clever with wrist pin weights.)

          We went with KB hypers for my son's 340. All street... just for fun and horsing around on the mountain roads. Pay close attention to the top ring gap instructions on the KB's if you go that route; the top ring gaps are a bit wider than typical due to the high position of the ring on the piston.
           
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          • nm9stheham

            nm9stheham Well-Known Member

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            That is good, but making sure of your tuning to avoid detonation is more important.
             
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            • stixx

              stixx FABO Gold Member FABO Gold Member

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              He actually said that his kids shouldn't hope for an 11sec. street machine... so yes stock or hyper would be fine.
              As long as he stays out of detonation.

              Edit: NM9 has it all covered.
               
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              • V24x2

                V24x2 Well-Known Member

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                Not 11's.....maybe down the road that would be nice! Were talking a 15 and 17 year olds here....a low 13 or high 12 would be plenty fast for first year drivers.....at least from a fathers point of view!! Lol.
                 
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                • V24x2

                  V24x2 Well-Known Member

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                  I meant 'hop in...' and corrected it since. Thanks
                   
                • 318willrun

                  318willrun Stomper 4x4... we kept energizer in business

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                  Ahhh. Got it. low 13's or high 12's I certainly wouldn't buy new pistons unless the cylinders are bad and you must bore it out. Speed pro work just fine and are cheaper.
                   
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                  • MOPAROFFICIAL

                    MOPAROFFICIAL Well-Known Member

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                    Exactly.
                    You really have to abuse and detonate hard before the hyper will shatter like mine, but I'm pushing mid 500 hp with a 4" stroke and damn near 200 psi cranking...nothing you can compare to the average street motor.
                     
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                    • krazykuda

                      krazykuda FABO Gold Member FABO Gold Member

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                      I prefer Speed Pro over the KB... I bought an engine from someone that had KB's in it and when we took it apart and put it back together one of the piston skirts chipped off... We didn't drop it or bang it, it just fell off when we were handling it to put it back in... Not sure if it was already cracked before we got it, but I went with Sealed Power/Speed Pro as they have a much thicker skirt....
                       
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                      • thesiren74

                        thesiren74 Well-Known Member

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                        If it makes you feel better i have cast egge pistons in my 413 and I've been beating the snot out of it for the whole summer, if you tune it and keep it detonation free they will last for years.
                         
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                        • rumblefish360

                          rumblefish360 so close yet so far away

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                          A lot of guys have gone pretty quick with the Hypers. 11’s are nothing for these slugs. I suggest pay close attention to the tune. But then again, that should be a basic thing no matter what your running.

                          I have used both slugs with no issues. In this case, cheaper is better.
                           
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                          • mgoblue9798

                            mgoblue9798 Active Member

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                            Speed pro pistons are boat anchors. Biggest "problem" with 340 is piston weight. I used the KB flat tops with scat I beam rods and reduced rotating mass by more then 5 lbs.
                             
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                            • 340doc

                              340doc Well-Known Member

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                              Which ever type piston you choose, all things being equal isn't going to dictate how fast the car goes. Just durability. I say build the bottom end strong and it will handle anything you throw at it in the future. There gonna want to go faster eventually, and you wouldn't want the short block to be a hindrance. Control the ET with the top end or gear.
                               
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                              • moper

                                moper FABO Gold Member FABO Gold Member

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                                There are differences. I like the KBs myself - lighter and plenty strong. Never had an issue with them.
                                 
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                                • MOPAROFFICIAL

                                  MOPAROFFICIAL Well-Known Member

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                                  One thing I'll correct is the part about balance and stock weight pistons. You dont want factory balance, nope... especially if you have the chance to correct it.
                                   
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                                  • nm9stheham

                                    nm9stheham Well-Known Member

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                                    So the OP will understand: Do you mean you want it balanced to a much tigher tolerance than factory (even if it is stock weight parts)? Or are you recommending he go to lighter pistons/rods and rebalance for that to get to lighter rotating weights?
                                     
                                  • MOPAROFFICIAL

                                    MOPAROFFICIAL Well-Known Member

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                                    Factory balance job wasnt the best. You'll have less wear the better the balance.
                                    Lighter rotating assembly is preferred to begin with, but not a have to. Trw forged weigh a ton and rev 8000 rpm in g stock.
                                    You can do the factory match weight pistons, but you wont be any better than 1960.... and that great for a old farm truck but bad for it being 2018.lol
                                     
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