Got the DOHC block checked out and it is good to go .040 over
I plan on boosting around 8-10 daily and around 13-15 at the track but am wondering how the hyper pistons hold up to boost. I know a few people have boosted over 12psi on stock cast aluminum so i assume they should be good if i get a good tune but thought i would ask.

engine:
93 block (3.661" bore)
stock crank
stock connecting rods (shot peened with ARP bolts)
Hyper pistons http://store.summitracing.c...2D100MM&autoview=sku
Crank scraper
main stud kit
'93 heads (ported and polished... valve spring shims )
'97 cams/carriers
96-97 lower intake manifold (gasket matched and polished)
96-97 custom upper intake (gasket matched and polished, copy of Kohburns short intake with 75mm T.B.)

turbo setup:
AiResearch TO4
50MM W.G.
"SRFL" B.O.V.
liquid intercooler (3" inlet and outlet mounted in trunk)
3" intercooler piping (about 4ft-5ft. total piping)
ported and polished exhaust manifolds (both fronts)
custom 2" crosover pipe into turbo (mounted under drivers engien vent)
3" downpipe into FlowMaster 40 series with dual 2.5" outlets and C6 corvette tips
Darth chip
SAFCII
42.5# injectors
Aftermarket FPR

[This message has been edited by SLOWnSTEADY (edited 01-06-2008).]

Hypereutectic pistons are stronger than forged - when they are hot. when they are not hot - they are roughly as strong as cast pistons.

so, yes - should be fine. just make sure it never knocks when first started. you'll notice many motors with hyper pistons are kindy "chattery" when first started. anyways - yes - hypers love it HOT.

quote Originally posted by Pyrthian: Hypereutectic pistons are stronger than forged - when they are hot. when they are not hot - they are roughly as strong as cast pistons. so, yes - should be fine. just make sure it never knocks when first started. you'll notice many motors with hyper pistons are kindy "chattery" when first started. anyways - yes - hypers love it HOT.

Does the strength go up with temperature? or does it fall off with temperatures higher than normal operating temps?

Well being an engine builder I have never heard of or read that the hyputectic are stronger when hot and stronger than forged i doubt it but if you have the technical data that proves it i would love to see it but a hyperutsctic pistons is a cast piston with extra sillicon added and that makes it stronger than normal cast pistons and you can run them with tight tolerances they dont grow as much but if you get detination the pistons wont last long forged is the strongest then hyperutectic

quote Originally posted by AP2k: Does the strength go up with temperature? or does it fall off with temperatures higher than normal operating temps?

yes - of course to a point - they are an alum alloy after all - which is why they so good - lighter. less rotating mass. well, reciprocating mass...
but - the sucky part - is they are stupid brittle when cold, and smaller. which is why the motor sounds like it has piston slap right after a cold start.
and, even when at full heat - they can be brittle & do not like ANY knock. which is the scary part of you wanting to hit 14 PSI boost. they are super super hard - but brittle. kinda like concrete - can really load it up - just dont "shock" it. intercool & careful tuning.

Go to kieth Black and look at the piston to wall claerance on the hyperutectic on a 350 chevy max is about 4 thousands and on a forged piston it will be about 8 thousands so there for the hyperutectic dos not have so much piston rattel on start up

quote Originally posted by engine man: Go to kieth Black and look at the piston to wall claerance on the hyperutectic on a 350 chevy max is about 4 thousands and on a forged piston it will be about 8 thousands so there for the hyperutectic dos not have so much piston rattel on start up

I may have the expansion backwards. but - either way - they are noisy when cold. have done 2 cars with these, same thing both times.

but - the strength - I know is true. at operating temps - hyper is stronger than forged. at room temp, forged is stronger than hyper. but brittle either way. hypereutectic is basicly a form of aluminum concrete. mighty strong, but shock it - it shatters.

[This message has been edited by Pyrthian (edited 01-07-2008).]

quote Originally posted by Pyrthian: I may have the expansion backwards. but - either way - they are noisy when cold. have done 2 cars with these, same thing both times. but - the strength - I know is true. at operating temps - hyper is stronger than forged. at room temp, forged is stronger than hyper. but brittle either way. hypereutectic is basicly a form of aluminum concrete. mighty strong, but shock it - it shatters.

Its true that hypereutectic metals expand slower than standard metal mixtures. You can run hyper pistons at far tighter tolerances because they wont expand enough to seize up. (Its better to run them with tighter tolerances anyway because the gap when warm will widen up because the cylinder wall will expand more than the piston )

I wonder then, would hyper be a good candidate for a high rpm engine? (say 10krpm or so)

NO there not as strong as forged if they where then they would be in the top racing engine like nascar NHRA TOP FUEL or any othere top racing engine

Stronger, weaker, from what I understand, it is the failure mode under detonation that matters. Both will get the job done and last a long time with the right tune. The difference is like the difference between, say, glass and lexan. Glass is really hard, lexan not so much. When you hit glass too hard, it shatters. Lexan tends to deform. Likewise with hypereutectic pistons and forged pistons. Hypereutectics, when you have detonation, will shatter. Forged pistons do not fail so abruptly; they deform first. They will still shatter if you keep beating them up, but if you're careful enough, you'll notice that you have a problem before that and can save your engine.

Edit: this is assuming you aren't approaching the tensile strength limits of the pistons.

[This message has been edited by Fiero Brick (edited 01-07-2008).]

quote Originally posted by engine man: NO there not as strong as forged if they where then they would be in the top racing engine like nascar NHRA TOP FUEL or any othere top racing engine

NHRA top fuel dragsters need forged because their spark plugs melt after the first couple hundred rpm of the race, after that they are running because of detination. hypers are stonger then cast like everybody else has said, you can stand a high rise building on one and it wound break but if you shoot a small nitrous shot at it and it runs lean and detinated the hyper will shatter and the forged will only have a pinging sound.

------------------
1986 Silver 5 speed Fiero 3.4 DOHC
Bored .30, Fully balanced and blueprinted
13.93@101mph as it is on the street. PFF's fastest N/A 3.4dohc!!!!
FOR SALE - MAKE OFFER!
... ... !
355cid 400hp/tq N/A SBC, 4 bolt main
Nitrous Oxide: 1st stage - 125shot direct port. 2nd stage - 75shot plate.
87 GT, Cryo Treated 5-speed Getrag, Gr8grip LSD, Spec Stage 3 clutch.

like I said the hyperutectic is better than a staight cas piston but cant take the beating a forged can if you tune the right there wont be a problem but if you mess up with being to lean for just a little while and get detenation you could have catastrophic faliure where the forged will not fail for a longer time

Engine man is RIGHT!
I wouldn't put cheap Hyper's in any engine of mine Unless I was building a Maypop! and Cast pistons are worse yet.
If your building any sort of performance based engine build it with Forged pistons there is a reason they cost more.
Especially a Supercharged engine a tad bit of detonation, and it will be gone!
Just because you cant here Detonation doesn't mean the engine isn't Detonating!
Any good engine builder will agree as well.

Hyper's were originally designed for the Claimer race circuit, That is if a car beat you in you could claim his engine for $150-$250 bucks the rule was intended to stop engine build cheating.

The Idea that they get stronger with Heat???? I would like to read any technical data you may have to back this claim up as well.
No I will not take Advertising claim's as proof.
I am not a High school punk believing everything in a Hot Rod Rag.

Why would you spend so much money on a turbo's, Porting and Inter coolers and skimp on pistons?

I've got a set of Silvolite hypers in my 2.8. They've seen 65K HARD miles. I opened the engine earlier this year and no problems or major wear. I'm planning to put them back in when I reassemble the engine.

[This message has been edited by Rainman (edited 01-07-2008).]

i don't claim to be an engine builder, but i have working in a machine shop for a short amount of time (years ago).

I am actually building about the same setup... 96' engine, with the ARP fasteners, and FORGED ROSS pistons... about $100 a piston (cost) not including the rings...

with the custom pistons i can decide on compression as well, and let me tell you, i believe it's better to setup the "ideal" combination for your application rather than trying to "make" hypers (who knows the compression rating) work in your engine. I will be spending some serious time and money into my 3.4L and the last thing i need is to see it blow up (in any event, lean condition or not) because of inferior pistons...

However, there are guys on this forum (as you know) that have made serious power with STOCK bottom ends... but those combinations are nothing more than ticking time bombs... (with the exception of the seriously "fine" tuned combinations)... you need to build the engine for the application even though these engines (any many others) have proven to last on stock internals...

i suggest you get custom pistons and complimenting rings... looking for 8:1 or 8.5:1 to retain "some" bottom end (with the compression at 8.5:1) prior to building the boost for the top end.

what are you doing for head gaskets? are you o-ringing? using ARP head bolts or studs?

quote Originally posted by mnstrfiero: .... However, there are guys on this forum (as you know) that have made serious power with STOCK bottom ends... but those combinations are nothing more than ticking time bombs... (with the exception of the seriously "fine" tuned combinations)... you need to build the engine for the application even though these engines (any many others) have proven to last on stock internals... .....

can you eleborate on options?
these aint SBC's with pages & pages of pistons, rods & cranks to choose from.
I think someone went and machined the block for 4 bolt mains
and there are some rod options - being you just need to match holes & length.

------------------
1985 Fiero SE - Plain Red 3.1 V6 Coupe
Engle18Cam DIS 4.10-4spd 7730 WCF Long Tubes Borla
D.A.M.M. - Drunks Against Mad Mothers

the hyperutectic will work if you dont go wild but if you wants peac of mind I would call Ross pistons I have had good luck with them and they are nice to talk to and act like they realy want to help with you project

I've worked with both Ross and CP and like CP's product better, although they are harder to deal with; they only sell to businesses, so you'll have to find a shop to place the order for you.

I run hypereutectic pistons in my Fiero 3.4l DOHC. I think 415 WHP and going on five years of running speaks for itself. You can blow up any engine. Forged or not. You need good control.

------------------
62 Buick Special
86 GT, 5-Speed
87 GT, 3.4l DOHC Turbo 415 WHP, 11.9 @ 118
88 Toyota Supra Turbo

My 2 cents worth. If you run the cast pistons, get the decks coated with ceramic. Calico is a decent company for this. You can keep some of the heat out and keep the strength from falling off. For some people that are advance with engines, finding a way to squirt oil on the underside of the decks will help a lot. Hypereutectics can indeed shatter from detonation. And believe me, you won't always be able to hear detonation. keep the boost down until you learn about detonation and some of the ways to detect it and suppress it.

Matt you did a great job of tuning and did it slowly overe time if he takes his time and tunes it the way you did he will more than likely not have any problems but if he is not as good a tuner or trys to go to far to fast matt do you have alchol injection to help

[This message has been edited by engine man (edited 01-08-2008).]

Well in case it helps, my engine has been knocking (preignition) like hell since I put the turbo on, so bad in fact I didnt even recognize it as knock. I've put it through some hard times (apparently) I've never seen any damage to any of the pistons, though I have melted holes right through them when running lean. Apparently running out of gas at WOT will do that to you. Damn fiero gas guages. The other time I melted I had a bad CTS and felt the lean, but tried to push through.. ehh bad descicions. At anyrate, its not like these pistons just shatter at the drop of a pin, there has been no evidence of chipping at all.

Why its knocking no one knows. I've had darth pull all the timing out he can, and I've been over the engine time and time again, in fact this is the second complete engine, but everytime I get into boost it knocks. This thing also hasnt idled since I put the turbo on. It acts like it wants to idle, and now and then it will be golden, until you turn the engine off and back on, then it will just stall every time you hit the clutch, until that next random time it works.

That being said though, I did have on shatter for unknown reasons before the turbo. Was making a clicking noise, I was running it gently through the RPMs listeneing, about 6500-7000 BAM! Nothing left bigger than a nickle, found pieces of piston lodged in the throttle body, somehow...

the options for bottom end...

well, this is what i have planned...

call the local "metal improvement shop"

i am cryo treating for 4 hours...
than heat treating ...
than shot peening...

roughly $300-500 for all the above services on the rods and crank

this is for the rods and crank, than everything will get balanced, cleaned, polished etc...

i will then purchase the ross pistons and the correct piston rings... remember that the correct "Stones" need to be used when honing the cylinders to get the rings to seat properly...

then, i will be getting the cams re-ground and the heads worked... the power is always found in the heads and cams...


Matt Hawkins- your combination is the acception (which i stated earlier). But you have spent a trumendous amount of time learing your combination and maximizing the power (correctly). however, that would be thousands of dollars of dyno time for someone that doesn't have the know how of independent tuning, not to mention that you are also running a metric based Stand alone! reason enough to turn me away from trying to tune that beast... a solid knowledge of the stand alone as well as dyno tuning would be needed to make it successful.... otherwise, anyone can blow up the engine in a matter of hours trying to fiddle with that combination.

If you have a chevy power book it tells you to just take small block chevy small jurnal rods naeeow the big end and bush the small end they are the same length and throd jurnal size are the same for the small jurnal and the V6 60degree

I would do the same thing with an Eagle rod instead of a stock Chevy rod athough some of the new Powder rods from Chevy are really strong.

Cryo is cool stuff, But Cryo then heat treat???? then shot peening hmmmm

I think Grind flash away then Shot peen then heat treat. Heat treating is suposed to make a part stronger and Cryo is suposed to stress releave correct me if I am wrong but thats how I remember it.
Shot peaning will only strengthen the surface, Grinding/Polishing the flash away will take out stress points
I dont think you would need to do all this to a stock crank if your under 450 hp I would use good rods though like an Eagle 3d though, and a good piston.
Most stock small block Chevys bottom ends are good for 500 hp as they are if set up properly and most of GM V6 desighn concepts are fundementaly based uppon the Little mouse motor technoligy there are exceptions though.
Like the even fire and the Odd fire V6 the Even fire crank looks like a break looking to happen, but yet I have seen one in particular with small block rods in it Blown with a 6-71 on top of it kicking Small block ford and chevy Butt!
And he claimed nothing fancy about the bottom end except good rods and pistons.

Another route for good parts would be directly from GM they have a good handle raceing stuff

i asked the local heat treating place for advice... "phoenix heat treat"

he recommended cryo first... "alight the something or other" in the material..
than heat treat to harden the surface...

than shot peen to finish off and obviously polish...etc.

aparently heat treating hardens the surface only... not the entire crank or rods.. but the cryo internally strengthens the material, and finally the shot to insure a strong (solid) bottom end for the 450+ neighborhood. Realistically, i don't believe i will be much over 350-ish to the wheels, but i want to have the added safety in case i decide to turn up the wick!

i will look into chevy 350 application rods however, and see if i can find anything relatively affordable.

I wouldn't run anything but forged in a turbo engine.

Considering how much the whole engine will cost you, the added cost of the right pistons isn't that big a deal.

I usually have Ross make pistons for me - the ones in my 3.2 tubo have been going for a lot of kilometers and up to 13 psi boost.

I think the forged VS cast or Hypers has been beaten to death, Forged being the way to go.

The thing is now I really think your getting sold anouther bill of good's Propper heat treating Will Harden the whole part weather it be a rod or a Crank its not just surface treatment such as shotpeaning.
But in order to get it Hot enough to do any good you will likly have to remachine the whole thing.
See if the guy has a Rockwell hardness tester a good shop should have one doing this type of work have your metal tested before and after! He should also be able to tell you how hard to expexct from the treatment.
If he doesnt have this tester find anouther shop they are not all that expensive as compared to buying the equipment to do the work.

The thing about Heat treat is very simular to Cryo it works by realighning the molicules in the metal, When useing heat your alowing them to move around to get closer to each other alowing them to get closer together so the part gets harder.
Very Simular to the way they make Forged steel as the Very Hot steel comes out of the furnace glowing red hot it then gets beat on by a huge Hammer thus its called forged as its been beat on with a 40+ Ton hammer makeing the steel more dense.

With a Cryo treatment its simmular as the metal doesnt know its cold instead of Hot But the Molicules do thow they move very slowly when cold and very fast when hot. The thery behind Cryo is the metal gets so cold the Molecules dont know its cold instead of Hot and they will move around the idea is that this will stress releave the part internaly but it wont make a part stronger, Some pepole put a lot of belife in this treatment others dont.
After all how can the Molicules move when its cold they know its cold they aint budging!

Like I was saying when I see it done right and a Rockwell hardness tester used on the peicess I will belive then.

Your under 400 hp just use a stock crank it can handle it and try to use a good powder rod from chevy there not to bad in price eitherand Ross will custom make pistons at a good price I have them in two of my Raceing Big blocks.

quote Originally posted by 86GT3.4DOHC: Well in case it helps, my engine has been knocking (preignition) like hell since I put the turbo on, so bad in fact I didnt even recognize it as knock. I've put it through some hard times (apparently) I've never seen any damage to any of the pistons, though I have melted holes right through them when running lean. Apparently running out of gas at WOT will do that to you. Damn fiero gas guages. The other time I melted I had a bad CTS and felt the lean, but tried to push through.. ehh bad descicions. At anyrate, its not like these pistons just shatter at the drop of a pin, there has been no evidence of chipping at all. Why its knocking no one knows. I've had darth pull all the timing out he can, and I've been over the engine time and time again, in fact this is the second complete engine, but everytime I get into boost it knocks. This thing also hasnt idled since I put the turbo on. It acts like it wants to idle, and now and then it will be golden, until you turn the engine off and back on, then it will just stall every time you hit the clutch, until that next random time it works. That being said though, I did have on shatter for unknown reasons before the turbo. Was making a clicking noise, I was running it gently through the RPMs listeneing, about 6500-7000 BAM! Nothing left bigger than a nickle, found pieces of piston lodged in the throttle body, somehow...

I've destroyed some hypereutectic pistons from several severe detonation cycles due to a bad ground leaning the engine out and they chipped very badly but continued to run normally for several hundred to thousand miles before the symptoms started manifesting. If you ever find a deformed spark plug electrode chances are a piece of piston did it. I thought it was caused by detonation until I disassembled the engine. It didn't harm the turbo much at all.

As for the detonation problem you had, I've learned from my 3900 troubles how suttle and difficult to find sensor problems can be. A tech friend of mine explained that unless there was a break in a wire a bad MAP sensor in most cases will ot set a code. In my case it didn't and caused the engine to lean out, datalogs showed detonation coming in around 5k plus rpm, and a MAP signal that never changed with throttle position. Personally I believe the sensors with a modified harness should use fairly thick gauge and long as necessary wires as well as the fuel pump for the best signals to and from the ecm. I plan to start from scratch building a new wiring harness at some point after I get the engine running properly by building the harness while it is in the car.

that's a killer collection you got there Mr. "doright".... lol


i will treat the crank as well, i will also have them test the peices before and after... why go to the trouble and not treat the crank, regardless of power expectation? Like i have mentioned before, i just want a SOLID, and reliable build (not a super exotic, max effort combination) but still have the right parts the first time. I would rather have "over kill" for the combination to run 200hp, than 400hp that is questionably assembled (inlcuding questionable parts).

quote Originally posted by Joseph Upson: As for the detonation problem you had, I've learned from my 3900 troubles how suttle and difficult to find sensor problems can be.

I've checked all sensors by scanning the ECM, all appears good. On top of that I've replaced the O2, then replaced that with a heated O2, swapped the MAP with a known good unit, changed half a dozen IACs (it also wont idle), TPS, and well most everything else. A good idea though. I've also added grounds.

As far as chipping, I've had three of these engines apart, all would have been subjected to the heavy pinging, and none have shown any indication of damage, well other than the holes I melted in the pistons, but that was from running lean. Im not saying these pistons are chip proof, or you should run with a pinging engine, just saying they're not made of glass.

quote Originally posted by Matt Hawkins: I run hypereutectic pistons in my Fiero 3.4l DOHC. I think 415 WHP and going on five years of running speaks for itself. You can blow up any engine. Forged or not. You need good control.

if you ever sell that turbo 3.4dohc, you message me fir6st with yrou asking price!

quote Originally posted by 86GT3.4DOHC: As far as chipping, I've had three of these engines apart, all would have been subjected to the heavy pinging, and none have shown any indication of damage, well other than the holes I melted in the pistons, but that was from running lean. Im not saying these pistons are chip proof, or you should run with a pinging engine, just saying they're not made of glass.

The difference may be that my troubles were more the result of erratic and premature timing advance resulting from the missing ground since detonation occured almost immediately on acceleration. Too soon for anything to get hot enough to melt, the pistons were chipped all the way down to the top ring on some of the pistons and all were on the same bank suggesting a combination of poorer injector performance pushing one bank closer to the detonation threshold. I know the detonation was audible inside and outside of the car.

I'm for the stock hypers since all failures I have observed at this point have been driver/tuner error instead of part reliability and strength. I'm interested in forged but at over $700 for a set complete with rings I just can't bring myself to do it without having first properly tuned the stock pistons and found them to be insufficient for the task. I have seen more evidence that they are through the accomplishments of others than to the contrary. I have yet to see any documentation regarding the circumstance of this discussion, that definitively proves one group of supporters is more correct than the other.

The on going debate regarding this issue is proof positive that the stockers have yet to be proven insufficient for the performance levels being sought. Forged pistons are definately stronger, and so is a steel crank as opposed to cast iron, the important question; is it necessary to reach your goal. An added sense of security alone does not make any additional horsepower. I've spent plenty of money discovering that. "If it ain't broke, don't fix it".

[This message has been edited by Joseph Upson (edited 01-17-2008).]