Its actually very simple to figure out.... the Gen 1 L98 with 64cc chambers was 9.5:1. The Gen 2 LT1 with 54cc chambers is variously quoted at 10.4 or 10.5:1. Where is the inconsistancy?

What's "same bore and junk" mean? Doesn't sound very "Advanced Tech".

 

i will only be running 93 octane , now the(hyper) pistons are starting to look a little better to me, thanks everyone

 

Superchargers and turbos are on all the time... spray is there when I want to play not pulling away from stop signs with a cop sitting caddy corner. Nitrous is also cheaper... *cough* I get it for *cough* $1.25 a lb. *cough*

 

It's great that we have this great forum to dispel myths that are constantly spread about. The wrong information can end up costing a fellow a good chunk of money needlessly

 

FWIW I ran a set of KB hypers in a budget bracket race car for 3 seasons and 300+ passes. Static comp was 12.8:1, NA.

For a guy looking to save a few dollars, they're a darn good buy. Take that money and put it towards the heads and valvetrain. That's where the big HP's at.

-Mindgame

 

Thats exactly what im talking about! all of my first engines were built using them and held up for years and left alot of high dollar guys scratching there heads.If I was building a motor to run consistantly n/a I would still use the hypers today.

 

It's not the compression, it's the detonation that kills cast and hyper pistons. They are strong but brittle- like glass. I've beat the snot outta KB Hypers N/A and never broke one. I've also done plate nitrous systems against them from time to time- also with good results, never encountering detonation.

Then there's a blower motor. I've killed 2 sets of them due to detonation (butted the top ring gap closed and ripped the ringland off the top of the piston, despite following KB's recommendations for very wide top ring gaps). This is the direct result of my own learning curve with a roots blower. I just can't get it out of my head that 9:1 compression with an old-school roots blower on pump gas is just way too high.

When they die this is how it will happen. The detonation doesn't really destroy the piston faces and blow a hole in them- it goes after the ringlands. Without detonation they'll probably last forever. But when/if you encounter detonation is when the problems will start.

You first indication of a problem will be when the motor goes "pop pop pop" through the exhaust at high RPMs. That is the sound of chunks of the piston ringland hopping up in the combustion chamber, bending the spark plug electrode crooked and then exiting through the exhaust valve, hanging it open and embedding chunks of aluminum onto the exhaust valve seat. If you're lucky, some of those chunks will also wedge in the "quench" area where the piston and head are close together, causing the piston to rock violently in the bore the next time it hits TDC, snapping off the piston skirt on the opposite side of the piston and cracking the cylinder vertically from about 1/3 way down the bore all the way to the bottom.

Ask me how I know.

 

That is not true.

hypers aren't glass. Get a little expierence with them, you will see that they aren't as terrible as the internet makes them out to be.

I've driven (personally) a supercharged mustang and been forced to be on it as it was pinging like you wouldn't believe. Its taken 20k miles of abuse like that.

My valve beat the crap out of my piston and dented it.

When we pulled the engine- we smahed the few remaining cylinders with the end of a wrench. they actually dented.

Its not glass. It can stand SOME knock. Infact, most GM gen III engines (at least trucks I know for sure) knock twice on startup.

But its not forged either, so dont build a TT 396 at 11:1 and then learn how to tune a car.

 

I guess I'm looking towards the root of the post. WTF is the point in building a 11.5:1 motor, building the bottom end up at all, then running a Hotcrap cam? With that small of a cam, running N/A, why rebuild the bottom end at all. If doing so, just have the crank turned, throw in new bearings/chain, and call it a day. You'll end up hurting the Hyperpathetic pistons before you hurt the crank/rods.

As for nitrous/hyperpathetics, I had good results with mine on my bone stock shortblock. Just pulled it out of the car a couple weeks ago. 95k miles of abuse, always ran a 150 shot. All of the bearings looked peachy, pistons all looked good, everything was in order, and I'm betting that bottom end still had some good life left in it. Yes, it saw 7200RPM more than once, 7000RPM a number of times, and 6800 RPM shifts were the norm (this was only the last few thousand miles of its life). Didn't burn a drop of oil either.

But I can't see building up a bottom end just to use Hyperpathetics. If you are just running N/A, either stick with a stock bottom end (aka super-budget rebuild if needed), or going all forged and throwing in a big bumpstick, and probably spraying it later. I couldn't fathom spending money on a forged crank, forged rods, and then saving $300 on pistons. You'd be much better off strength wise to run a stock crank, forged rods, forged pistons, and since your average forged crank is $600 on up, you'd end up SAVING $300 over the other way.

IMO, if you are going to dump money into the bottom end, spend the extra money and do it right. That way, if you want to toss more power into it later, you can vs. not being able to because it won't handle it.

 

an excellent point.
Most engines i've seen the fail after FI/N20 that aren't due to a manfunction (timing, fuel, backfire) do so due to wear, not component failure.

worn bearings that eventually spin or something of that nature. I havn't seen many that just randomly cracked a piston.

if the force is applied evenly over the piston, it really shouldn't rack within reason.

Ive seen 3 hydrolocked motors, none had piston top damage. why? force was distributed evenly, and it was an incredible force. With a relatively big piston (4''+) we should be ok as long as we dont detonate or make an abundance of power.
Ironically, the smaller bores are the ones less prone to detonation so you can run more boost.

Thermodynamics can be a real ***** sometimes, but at least she is consistant. If someone starts violating the conservation of mass or energy in non-nuclear activities, I'm going to throw a fit.