which would be best for street driven car w/ 11.3 to 11.8 comp ratio, no blowers or n02, and why one is better than the other? I want something that is going to last , still going to use the hotcam thanks for any info
shaun

 

in a nutshell

hyper: don't have the chance of making clanking sounds, less cylinder wall wear

forged: possibliity of a clanking engine, more cylinder wall wear, stronger.

what your hp goals and how "driveable" you want your car to be will determine what you want.

imo i would get forged if you are debating between the two, b/c it is always better to overbuild then to underbuild and break something. but then again i like the clanking sound of forged internals and valvetrain noise.

 

If you are not planning on using nitrous then hyper cast pistons are fine and may even help make more power due to the fact that cast pistons allow for tighter piston to wall clearence(less blow bye) and they are lighter then forged.They wont hold up to forced induction or N2o very well so if there is any chance of running either forged is the way to go.

 

Check into the KB hypers. Inexpensive and light, they'll hold up to quite a bit of power NA.

-Mindgame

 

For some strange reason, people believe that forged is a prerequisite to building a street strip engine.

The only time forged or billet is better is when forged is needed. Kind of like fuel injectors.

 

Unless you're using a power adder go with the "hypers". You'll be able to run a tighter wall to piston clearance for less blow-by, longer life, and less noise, plus they're lighter (as most people have already said)... Spend the money you saved on a good forged crank and rods. Forged is good because it isn't brittle like cast components, and it can transfer heat better, so the face of the piston can handle the higher heat caused by stuff like high compression (If you fill up your n/a car at the strip you're probably in this category), boost & nitrous.

 

u can use the hyper pistons to a degree with nitrous without any priblems its when you use more than id say 125 shot is whenthe hyper coating starts pitting off and you get pits in your pistons and sometimes in valves because the burning hyper material can stick to valves and burn holes in them as well, 150 is where the coating ususally comes off but i say 125 to be safe, but then again i will never use nitrous myself, too expensive of a power adder best bang for buck is supercharger or turbo, once u buy it its there no running out

 

Let's just break right there. What "coating" are you talking about?

Hypereutectic aluminum alloys are simply alloys with high silicon content (12% or more). Coatings are a different matter all together.

KB's website would be a good place for you to start reading so you know what it is you're talking about. Otherwise people who are trying to learn just end up dazed and confused.

Now we can just "X" the rest of this out....

http://kb-silvolite.com/article.php?action=read&A_id=1
http://kb-silvolite.com/article.php?action=read&A_id=2

Oversimplified but that's just what the doctor ordered in this case....

-Mindgame

 

sorry i was mistaken, but it still does what i said it does with nitrous and pits the piston

 

Its not the nitrous itself that pits the pistons, as mindgame pointed out hypereutectic cast pistons contain a higher silicon content then normal cast and are very strong in n/a conditions.Its actually the heat that kills the cast pistons caused by the higher heat and pressure nitrous introduces to the combustion chamber.Cast pistons will melt or crack much quicker then forged under extreme conditions while forged hold on longer and tend to go "plastic"before failing.I have actually used a KB Hyper piston with a 250 shot that lasted a few years and never did let me down but I wouldnt suggest it would hold up for anyone else as I beleive I got "lucky", Just pointing out that these hyperutectic pistons are amazingly strong for a cast piston. Also detonation will cause the pitting or flaking you describe even on a forged piston with to much ignition leed and a lean fuel mixture.

 

They Hyper's will blow out the engine w/ as little as 3* to much timing. They're initially lighter but need a lot of weight added to balance them. Which negates the cost saving and the lightness benefit.

The only thing they have going for them is the tight clearances. I read in one of Vizards books him reporting zero blow by w/ them. Compared to a forged which showed 2-3% or somewhere around there.

 

I dont know where you get your information from BDC95ta but thats not true, hyperutectic pistons are strong castings and detonation will kill any piston forged or cast as well as eat up rings.I doubt 3 degrees would kill it unless you are experiencing SEVERE detonation. And as far as balancing them out that is completly untrue,I worked as a machinist for 2 years and I havent ever needed to fool around with weight matching a good name brand piston.Usually they are very close to one another and its the rod and crank that need weight added and subtracted.

 

Listen to n20ta2! I would go with the forged pistons and here is why, you want to run 11.3-11.8 compression which means aluminum heads and premium pump fuel or better. Since you say mainly a street car, you'll be tempted to run lower octane and say "I just won't get on it." Ya, right! Been there done that rebuilding tomorrow. Even though you don't here pinging you could still be doing damage to your engine. Drop down to say 10.5:1 and then you might be OK.

 

You speak from experience or reciting what you have read.

Not a flame...but seriously, stock is 10.4:1.

There are an army of guys running around 12:1 with hyper-junks with no problems AT ALL....and running damn good to boot.

Hyper-junks(which I call them, but they actually are not bad at all)are fine for most cars out there.

You do not build a high compression engine that was setup to run 93 octane and one day you decide to save $2 at the pump but put your engine in danger by running 87 octane.

 

i dont really think lt1's are 10.4 to one i may be mistaken but think about this for a second, old school 350's use same bore and junk cause lt1's are much different,w ell they use the same type of piston cept hyper on lt1's cast on old schools, well the old school has a 64 cc combustion chamber and last night i cc'd a set of 93, 94 and 95 lt1 heads, each head was the ame 169 cc intake runners, 55cc combustion chamber to be precise, not how does an oldschool 350 run 10.5 - 1 compression and a lt1 with the same pistons, valve reliefs and smaller combustion chambers also achieve 10.5 - 1 ratio?? me and a old school racer are tryin to figure this out