Based on comments in another thread, I thought I would give back to this community and post an expert engine builder's piston advice here:

@jb78L-82 summarized it well:
The issue with Hypers is they do NOT tolerate detonation well of any sort like a forged piston..No detonation issues and I would predict that Hypers are fine......

This piston advice is based on my friend’s 3000+ engine builds and my listening and research and quotes from multiple sources. My best friend builds mostly common sense drag motors, and his customers run them til they break, so he gets to analyze a lot of broken motors. He’s seen 100’s where the pistons came apart, and I’ve seen at least a couple dozen of those.

The 3 piston types are based on three useage categories. Daily street use, hi perf street, and race. The pistons recommended are cast, hypereutectic cast, and forged. The issue is exactly where the boundary lies between them. You will find a wide variety of opinions. Especially where the boundary is between hi perf street and race, (concerning hyper and forged pistons.) This is where many of the failures happen, as in pushing a Hyper piston a little too far, and the results are always catastrophic. It’s the number one failure point he sees in this type of engine. And it all depends on: how hard are you going to drive it?

My and Jeff’s (conservative) advice:

If you want to rev to 6500 or beyond, or do it regularly, or drag race more than a couple times, have a power adder, or be able to tolerate a little detonation, or bad gas, or a tuning malfunction, run a carburetor, or not run a knock sensor, forged pistons give you some extra insurance against catastrophic failure. It makes the bottom-end almost bullet proof in street use. (Especially also with ARP rod bolts) Which is exactly why Chevy put them in old-school Hi-Perf Smallblocks and Bigblocks in the first place. (Warranty)

Hot Rod Magazine:

Cast and hypereutectic pistons are ideal for engines that witness a lot of street use with just the very occasional weekend dragstrip visit.

If adding a power adder like nitrous, turbo, or supercharger, we recommend avoiding the use of a cast or hypereutectic piston.

Forged pistons are always considered an upgrade to cast and hypereutectic pistons.

Engine Rebuilder:

Many experts say any engine that is capable of producing upwards of 400 horsepower, revs beyond 6,500 rpm, is boosted or uses nitrous must have pistons that can take the punishment. (Beyond cast)

Manufacturer advice: (aggressive)

In many instances, the OEM hypereutectic pistons can handle engine modifications that boost power up to 30 percent or more over stock.

One manufacturer said hypereutectic pistons can usually handle up to 1.5 to 2 horsepower per cubic inch of engine displacement. Beyond 2 horsepower per cubic inch, they would recommend upgrading to forged pistons. (500-700HP small blocks)

****provided the fuel mixture and timing are correct so the engine doesn’t go into detonation or preignition.***

(Typically this means computer controlled, with fuel injection, and especially knock sensors, aka LS motors, not gen 1 small blocks )

Common Sense advice: (Conservative)

As everyone mentioned, there is no real limit. The limit is detonation. With high cylinder pressures the slightest detonation may destroy a piston instantly. Where as a forged one may last longer and take more abuse.

Id say keeping the compression moderate at around 10:1 at best and build it for 5500 rpm at best..... (Cast)… You can go a little higher in rpm on Hyper-cast. How high ?? The more you push a Hyper piston, you better have computer control, knock sensors, good tuning etc.

 

I agree with your advice. I believe it is best to overbuild a little when it comes to pistons. You can get 4032 material that fits with very tight wall clearances and will handle a lot of abuse. I've run them in my 555" over 8000 RPM for a long time. If you're going to get real crazy....move to 2618 material.

Also remember...there is a HUGE quality difference in that $99 set of Hyper's you bought vs the ones GM and Porsche use in their high $$ engines. Not even in same league. I'd be more apt to trust a set of OEM cast from 1969 as some of this trash coming out today.

And having EFI, variable cam timing, and total engine management for temp, timing and fuel control adds a LOT of safety margin. The computer won't let you hurt it...it tries to protect the engine by pulling timing and adjusting fuel in about a nano-second ebfore the next spark plug fires.

Build it strong and safe and you never have to worry about it!

JIM

 

Good info. Sometimes the hypers are a good compromise vs. (usually) more expensive forged if you are trying to contain the budget, and they do seal up really well with tight clearances. I have run hypers on several street / pump gas motors now with great results, and two of those saw 6000rpm on a regular basis. I have also seen major damage in a big block Pontiac (brother's) after he ran a few seasons on KB hypers and had detonation problems while running really borderline compression, and took awhile to sort out. The top of two decks were literally broken out above the top ring.

On my most recent street motor I used Sealed Power / Speed Pro hypers at the recommendation of my machinist, as he pointed out they set the top ring down further and the top ring land is quite a bit thicker. Nothing wrong with good quality cast pistons, either, but research as there is differing quality among the manufacturers.

It still comes down to a safe tune and controlling any detonation, as pointed out already, to keep the pistons and bearings in the motor. People talk about wanting more and more compression, but need to cam it and have the balance of the components compatible with that CR if they are going to run typical fuels.

 

A really nice summary of the issues using different pistons, Leigh. Thank You.

 

x2 good stuff. As you posted GM gets away with using them as their fuel/spark managing system is fantastic. WHen hypers go they are like a grenade they take out pretty much everything.
Got lucky with a solid lifter 350 that saw over 7k regularly wouldnt recommend it though. Those cheap crank kits are tempting with thier low price tag but if you are going to be hard on it spend a little more at least get a cheaper forged piece. Tuning with an 02 sensor is good insurance for longevity if you cant read plugs well.

 

 

I see my engine was on the border line of needing forged. Perhaps the combination of the new E-fuel here and high-RPM's I just tipped one over the edge.

 

I'm running a 500hp small block with a 150 shot on top of it with hyper pistons. Have about 100 passes on it. I do run race gas and am conservative with the timing though.

 

Good job Leigh! That is a good a good write up an I agree with what you outlined. I also agree with Jim in overbuiling.

Mike

 

I've used Mahle, Diamond and Manley forged pistons. The engine builder would not even consider hyper pistons. He said the mid-range price forged pistons cost so little more buying hyper pistons just don't make sense. The Mahle pistons in LS1 are a bit noisy on cold start but the block was right at the over bore limit. After it warms up a little bit you can't hear a thing. The LS1 blocks have such thin cylinder liners. I've run it for over 10 years with no trouble at all. The Diamond and Manley pistons were dead quiet on cold start.

 

My builder told me the same about Hypers when i innocently mentioned them during the rebuild parts selection process. He told me that he would NOT do my build with anything less than Forged pistons since the difference in cost is not that great but the reliability/durability of a forged is just so much better and not worth D**king around with hypers. I never brought it up again and we went with JE Forged racing pistons for the 355.....I have never looked back and glad I took his advice. I tell people all the time, sub 400 gross HP to around 5,500 RPM, go Cast pistons. Anything else, 400+ Gross HP 6,000+ RPM, Forged the whole way.

 

Piston design has come a LOOOONNNG way. Much of piston noise even with looser clearances can be designed out of it. I ran my 4032's at .0045-.0055 clearances (different pistons) and they were dead quiet even when cold. My current 2618's can be heard slightly when cold...but not bad.

JIM

 

Same thing goes for forged connecting rods. The mid range priced forged con rods are very affordable.

 

I run FORGED pistons in my stroker.. 10.5:1 CR ..9 +years on the build , no issues.. a little noise in cold weather start-up, but can take abuse without problems ...

 

Thanks for all the info guys! Mahle 930200130 pistons have been purchased

 

Nice 4032 choice w/ thin metric ringpak.