There are two camps on the hyper pistons, one side of the camp fire would never use them again based on past experience or because they have read so many stories of them failing even under stock boost levels and often on cars running more than stock boost. The other side of the camp fire will say they are fine for a normally aspirated engine and OK in a turbo engine at stock boost levels.

I think both sides would agree, that a good used set of factory pistons, in the right size, are going to be better than any hypers available today. It's hard to go wrong with forged but the bore has to be a bit wider than for cast so a trip to the machine shop is going to almost always be required.

 

Thanks. That was what I was wanting to know. I'm planning on more boost than stock, just nothing crazy. Sounds like I should ditch the hypers just to be safe.

 

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Duplicate post, please remove if possible ...

 

The problem with hypereutectic pistons is their inability to absorb detonation.

With a perfect tune and nothing to induce detonation they could last years.

However, any detonation while accelerating, will destroy the brittle ring lands in approx. 1 second.

As you already have what you have, give it a try and best of luck.

I don't say that sarcastically, its possible to get some life out of them if you never detonate.

Detonation occurs when the A/F mixture "explodes", rather than burns rapidly after the spark plug fires.

Some things that promote detonation are low octane fuel, incorrect timing, overheated engine, overloaded vehicle, oily vapor from the PCV system entering the engine air intake and elevated boost.

Octane is the fuels ability to resist detonation, also known as spark knock or pinging. Low octane fuel "explodes" easier than a higher octane.

For reference pre ignition occurs in the same place but is different than detonation.

Thanks
Randy

 

I seem to have a problem with a duplicate post and can not edit or remove one.

Thanks
Randy

 

my take is if you are deep enough in the engine to hold a piston in your hand then forged is the way to go. Not many people can stand staying at stock boost level.

 

Im in the camp that wont use hypers for any application. Good used factory or forged = piece of mind. I've quickly and waaaay toooo easily busted two engines with hypers with as indicated above only a second of detonation at 12-15psi. These cars get fun at those levels of boost and the hypers just can't take it.

 

I ran 18 psi daily on hypers for a few years. (I did use a wideband!) I eventualy broke the clutch and decided to also tear the engine down at the same time. There was still nothing wrong with the pistons, but, since I was throwing my saved-up stash of nice parts at the engine, I went with some forged ones.

I don't really recommend using them, but if you're careful they'll work. When I bought the car it had two melted pistons and the wastegate vacuum line was MIA, so they can be trashed.

 

The guy that rebuilt my 2.5 L Had trouble finding +.40 pistons as needed after boring to get them "round" again. He finally found a set of +.40 KB's and not thinking about the hyper issue I gave him a green lite to install the Kb's. After the build was complete and paid for a bit of research proved to me that Keith Black does not produce ANY Forged Pistons, their ALL Hyper*&^%*&^%:bang head And a call to their Tech department and the conversation I had on the subject I was told by the tech guy to not go over 10 LBS of boost, sooooo? What's another pull down, plus re-machine and put together with another $450-$500 just in 4 more pistons rite? They say it's ah learning experience but DAM. She's threatening to have ah couple yards of 6 bag mix poured on top of the money pit:shrug:

 

Thanks again for the info, guys. I've got plenty of time to make a decision on pistons as I'm still deciding what to do with the motor. Either put it in my NA 88 Daytona, or put it back for the boy's Omni and go DOHC on the Daytona. Another question though, most of the forged pistons I'm seeing use slightly larger pins. Will I need my rods machined or replaced to go forged? My thinking on this motor is a quickie ring job (and pistons) and keep things fairly mild. If I have to buy rods, then the snowball effect will kick in. Why buy forged pistons and good rods to hold back on boost? Bigger turbo, ported head, etc. Not ready for that jump just yet.

 

You can use your existing rods, they will need to be honed to fit the larger pins, IF you opt-in for the larger pins. Some of the vendors, on some of the brands available can provide standard size pins.

 

Some of the vendors, on some of the brands available can provide standard size pins.

That's what I was wondering. Thanks.