Pistons, Forged or Hyper
Thread Starter
Le Mans Master
Joined: Apr 2005
Posts: 6,339
Likes: 416
From: Seattle Area WA
Pistons, Forged or Hyper
This subject is probably as controversial as what cam to use in our 327s. For your everday or rather weekend midyear hot rod Corvette,
would you select the KB 157 Hypereutectic pistons or the TRW 2166 forged pistons?
would you select the KB 157 Hypereutectic pistons or the TRW 2166 forged pistons?
Race Director
Joined: Jan 2000
Posts: 13,014
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Personally I'd use the forged so I would never have to worry about them. But hypereutectics are Ok as long as you gap rings looser and respect their limitations. RPM and detonation.
JIM
JIM
Team Owner
Joined: Feb 2005
Posts: 32,519
Likes: 1
From: central America
St. Jude Donor '08-'09
I'm running hyper's in mine, largely because I'm not a dedicated racer, I'm not going to run nitrous and I don't plan on trying to spin them over 6000 rpm on a regular basis. For me, I wanted something better then the stock cast, but was less expensive then the full forged. Good for a run down the strip every once in a while, and maybe an autocross or two, but nothing too extreme.
What's the rest of your rotating assembly?
trw
What's the rest of your rotating assembly?
trw
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
I've got KB lightweight hypers in my current short block at 11.3-1 CR. It makes maximum HP at 6200 and spinning it there or beyond has never been a problem in going on 25K miles. I've done some autocrossing and enjoy it in other appropriate places now and then. I talked to my machinist when I built the current block a couple of years ago. He does a lot of work for and builds engines for many drag and oval racers in the area. He was very straightforward and told me when he first started using them, he had some problems because he did not address the special gaps required for them. After conferring w/ KB, he realized what he did wrong and has used them w/ great success since. He says they're very popular w/ bracket racers and economy class oval racers around here.
Le Mans Master
Joined: Jul 2004
Posts: 6,248
Likes: 4
From: Lancaster PA
Originally Posted by 427Hotrod
Personally I'd use the forged so I would never have to worry about them. But hypereutectics are Ok as long as you gap rings looser and respect their limitations. RPM and detonation.
JIM
JIM
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Racer
Joined: Sep 2004
Posts: 424
Likes: 2
The new Z06 uses Hyper. If you want to use any kind of forced induction or No2 use forged. Forged can be noisy (piston slap) at start-up. K-B's are not real popular with some engine builders, look at Speed Pro they have friction coated skirts. I saw recomendations in one of the car mags about Max. HP for Hypers, probobly should check with the manufacturer.
Burning Brakes
Joined: Sep 2005
Posts: 993
Likes: 3
From: Iowa
Hypers run in my engine that hits over 7000. We also run our gaps tighter than recommended. We consulted our engine shop that has set up and raced a lot of these and they report having very few problems. Since all they build is serious race engines we took there advice and have not had any problems. Most of the ring expansion issues the kill hypers come from poor tunes that lead to excess heat.
