I have a built 350 that is at 10:1 compression and running about 400hp. I really want to add a supercharger but my good mechanic friend told me that hypereutectic pistons (which I have in right now) don't do well with power adders, especially nitrous. Is this completely true? If so, how much boost can I run and be safe with? Thanks in advance and if this has already been posted somewhere don't flame me, I'm new. =)

 

Hypereutectic pistons are unforgiving will shatter if you go lean or detonate with a power adder, where a forged piston might warp or melt and burn but generally keep working to a degree. 10:1 is pretty high compression for a supercharger.

 

To be honest with you, I have absolutely no experience with any type of poweradder. What do you mean by "A high compression ratio for a supercharger?"

 

I have many many runs on my stock 350 TPI with 150 hp nitrous. These are cast pistons and are doing fine. NOS=cheap horsepower

 

A cast piston is more forgiving than hypereutectic.

 

Don't like hypers eh? Bad Experience? =P I've also read that hypers are cast just with silicon content. There's also alot of threads with people that have same stories like the guy above posted. I really don't know what to believe. I guess I'll just have to ask around some more.

 

No, I love them, use them all the time. They're just not the right piston for every application.

 

I ran them on a 150 shot of nitrous in a 305 and i ran them with 8ibs of boost on a 350 and no problems yet.

 

They are cast (unless they're forged hypereutectics, but those aren't common... even then, a forged piston is still cast before it's forged), it's the metallurgy that makes them different. When cast, the alloy contains more silicon than is able to dissolve in the molten aluminum. That leaves little crystals of pure silicon scattered throughout the piston when it cools. That makes the piston much harder, so it doesn't wear as quickly when it scuffs against the cylinder walls. It also makes the piston much more temperature-stable so it doesn't expand as much with heat, so that the cold piston to cylinder clearance can be smaller to reduce blow-by and piston slap on cold starts. That's why hypereutectic pistons are best for naturally-aspirated street engines.

The downside is that a hypereutectic alloy is more brittle than aluminum alloys with less silicon content. Under unusual stress, cracks will quickly form between all the little harder grains of pure silicon embedded throughout the alloy, and the thing will break in half. A piston (whether cast or forged) made from a eutectic or hypoeutectic alloy doesn't have these little silicon stress points scattered all through it, and so isn't likely to break. It'll warp or melt gradually.

The key word above is unusual stress. If nothing ever went wrong, a hypereutectic piston would be perfectly adequate with a power adder. If Bad Things happen, they'll fail catastrophically.

 

I heard a lot guys try to explain why to stay away boost or big hits of nos; and reasons given by Apeiron is as good as any. Especialy the part that any failure is catastrophic and thats a good word forit cause nothing is left.
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I heard a lot guys try to explain why to stay away boost or big hits of nos; and reasons given by Apeiron is as good as any. Especialy the part that any failure is catastrophic and thats a good word forit cause nothing is left. If you dont have
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I heard a lot guys try to explain why to stay away boost or big hits of nos; and reasons given by Apeiron is as good as any. Especialy the part that any failure is catastrophic and thats a good word forit cause nothing is left. If you dont have to dont use them.

 

So I guess theres only one thing left I have to ask. Apeiron, would you leave the pistons in and add a poweradder, or would you take the engine out and put something different in for pistons?

 

If it was me, I'd rebuild it with forged pistons and for lower compression.

 

So basically just bigger heads and some steels?

 

Bigger heads or dished pistons. What do you mean by "steels"?

 

Steel Forged but dished are better or worse? They will give less compression correct?

 

Pistons aren't steel, they're aluminum. Dished pistons will lower the compression.