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Discussion Starter · #1 ·
For a daily driven application, with no power adder?

I've searching on other boards, and I see alot of people getting steered away from forged pistons, in favor of Keith Black or Speed Pro hypereu pistons.

I've seen them recommended for everything from stock 302s, 351s, on up to 347s, 393s, and 408s.

If it's true, what makes these pistons "better" for a DD, with no power adder?

Why would they last longer?
 

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The Hypers are lighter than forged and don't expand as much so the fit is better from cold start through full warm up (less slap and skirt damage). The problem is that if they break, they shatter like glass instead of just cracking or melting down. They're supposed to be good for a DD performance application if you don't get real carried away. Once you start adding nitrous, a blower, or high compression, it's time to go with forged.

Hot Rod magazine had a great article last month on a 5.0 Mustang engine that lost a valve head on the dyno at 6500 rpm. Where they would have poked a hole in the piston if it had been forged, the Hypereutectic piston shattered instead and filled the engine with shrapnel. The whole engine was junk including the block and both heads. IIRC, they didn't save anything. It's a good read.
 

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Keith Black Silv-O-Lite "Claimer" performance pistons use high ring placement and the low thermal conductivity of the hypereutectic alloy to maximize engine efficiency. They are 30% stronger than ordinary cast pistons, heat treated, machined for higher compression ratio and reduced cylinder wall scuffing.
I am running the Silv-o-lites in my truck (#1160 = .030)
 

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Larston said:
The Hypers are lighter than forged and don't expand as much so the fit is better from cold start through full warm up (less slap and skirt damage). The problem is that if they break, they shatter like glass instead of just cracking or melting down. They're supposed to be good for a DD performance application if you don't get real carried away. Once you start adding nitrous, a blower, or high compression, it's time to go with forged...
What he said. :thumbup

Hypereutectics are stronger and more ductile than plain cast pistons, but not as durable as forged. As I understand it, the difference in expansion rate is due to a difference in the amount of silicon in the alloy to suit forging vs. casting. I honestly don't remember offhand which direction the difference is -- in other words, I don't recall whether forged pistons use a lower or higher silicon content (and therefore whether the silicon increases or decreases the expansion rate).

And incidentally, it was the 93 Mustang that went back to hypereutectics. 92's were still forged.
 

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The Anti Yam!
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Chuck said:
And incidentally, it was the 93 Mustang that went back to hypereutectics. 92's were still forged.
You sure?
I coulda sworn 92 was the conversion year.
 

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Ex Navy Nuke
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Forged are the best. For a DD Hypers are good enough. I went with forged because I went high end on every piece in my engine and I wansn't about to skimp on pistons(plus I got a good deal on them).
 

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Discussion Starter · #11 ·
RLKBOB said:
Forged are the best. For a DD Hypers are good enough. I went with forged because I went high end on every piece in my engine and I wansn't about to skimp on pistons(plus I got a good deal on them).
I was under the assumption that they were the best as well, but I started seeing guys over at corral, saying that they were a "better" choice for a car that saw alot of miles.

If they're only adequate(sp), then they seem kinda pointless to me. You can get forged pistons, for not that much more.

Larston said:
The Hypers are lighter than forged and don't expand as much so the fit is better from cold start through full warm up (less slap and skirt damage). The problem is that if they break, they shatter like glass instead of just cracking or melting down. They're supposed to be good for a DD performance application if you don't get real carried away. Once you start adding nitrous, a blower, or high compression, it's time to go with forged.

Hot Rod magazine had a great article last month on a 5.0 Mustang engine that lost a valve head on the dyno at 6500 rpm. Where they would have poked a hole in the piston if it had been forged, the Hypereutectic piston shattered instead and filled the engine with shrapnel. The whole engine was junk including the block and both heads. IIRC, they didn't save anything. It's a good read.
Good info. I'll have to thumb threw that HRM you're talking about, to read that article...I must have missed it.

When you talk about the positives for the hyper pistons, is that stuff only "marginally better", or is it something that means the difference of having a motor last for 50k as opposed to 100k. I know there are plenty of variables, that will make an engine last a long time, versus one that shits the bed after 50k, I'm just trying to see if the positives you listed make them a "better" choice.

Does that make sense?
 

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also hypers are lighter than the low cost forged pistons(TRW) which will make happier and longer bearing life. When I build a motor I look at what its going to be used for. If no power adder and I dont want to spend 500+ on quality forged pistons I would go with the kieth silv-o-lites. or something in that nature. I am not to big of a fan on heavy TRW forgeings. Just something to think about when building a motor. The lighter the rotateing assembly the faster it will rev. My lightweight internals in my 351w revs a whole lot faster and smoother than when I had factory rods crank and TRW pistons.
 

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Gacknar said:
You sure?
I coulda sworn 92 was the conversion year.
Nope, definitely 93. Sucks, since I'm stuck with the only year with hypereutectics in that body. On the other hand, I've absolutely run the piss out of that engine since 34.5k, and at 172k it loses less than a quart of oil in 5k miles. Gotta love high nickel blocks. :thumbup

Incidentally, as for the explanation for the weight difference between forged and cast pistons -- it has nothing to do with the density of the material, and is purely due to manufacturing requirements. You make a forging by heating the material and slamming it between two dies. You have to design what's called "draft" into the parts so that the inside die -- the one that forms the underside of the piston and inside of the skirt -- can slide back out after the piston is formed. Basically, the opening in the bottom of the piston has to taper larger as you go down.

With castings, you can use multi-part casting dies for the inside, and make nearly whatever shape you want. The die can come out in pieces, so the skirt doesn't have to clear the entire die at once. Heck, taper them the opposite way if you want to. Or put a thickened ring around the inside of the base of the skirt. Point is, it doesn't matter -- it gives the designers more control of the wall thickness everywhere in the piston.
 
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