I'm looking at buying a short block from jasper and it comes with hyper(sp) pistons. Is it worth it for me to upgrade to forged pistons. I'm not looking at making killer HP I just want it to rev to 6000 safely. FYI I'm getting a steel crank also. Any advice is appreciated.

 

It's my understanding that the Hyper Tech Cast Pistons should be good for up to 400 HP and the 6000 RPMs you're talking about. Just make sure that you get the rotating assmebly balanced, before putting it together.
From what I've learned, the forged pistons need more clearance, and are therefore subject to creating more blow by, and some oil consumption over time, but are definately recommended for high performance applications, racing, high(6,500 +) rpm and nitros oxide intended usage.
Assume none of these fit your intended useage.

 

No your right its not a race car. I figured forged was overkill. I'd rather spend the money on a steel crank.

 

A hypereuthectic piston is plenty strong for your application even if you run small doses of nitrous. For the buck they are a great piston. I have tensile strength charts on the various pistons and a hyper piston is actually stronger then a forged but it is also brittle. It breaks if overloaded where a forged will bend. Go for it. Do you really need a steel crank?

 

If I want to take this thing over 5500 rpm I would think a steel crank would be required. I was thinking of the zz4 with its hyper pistons and steel crank. It redlines at 6000.

 

Tony,

I believe the term you are looking for is hypereutectic. It refers to the cast process when a certain amount of silicon alloy exceeds the percentage point of the toatl metal cast, usually aluminum and in this case silicon. IMHO forged pistons are/have been overrated. I have run both hypereutectic and cast pistons both on N2O and held up very well. (Although the cast are not truly reliable in a N2O motor, I did it out of curiosity and budget restraints). When I changed to eutectic they proved extremely reliable and made well over 50 passes on heavy nitrous runs. It is not how strong your piston is..but if you are meeting the correct air/fuel ratio. If properly accounted for, the correct fuel mixture will easily cool the cast piston properly. Of course, a heavier fuel mixture means decreased burn efficiency, which in turns contributes to slower ET's. Thus, the Bubba factor then becomes involved opening Pandora's box to see how lean he can run the mixtur to optimize HP and ET, and he's spending Sunday tearing down his motor to replace burnt pistons. Been there done that.

Invest in a good set of KB eutectic pistons (or SCAT) and rods, and keep your cast crank...you'll do fine.

IMHO opinion, rods are the heart of the bottom end (similar to the cam being the heart...) some people may disagree....but the lighter mass you have to rotate, the easier it is on your cast crank.

 

Sorry I'm far from an expert in this area but I figured a steel crank is stronger and lighter and would help the engine rev higher.

 

I assume we are talking about a small block? Steel cranks are a racer's choice...if your budget allows. If you can afford a steel crank and the added peace of mind by all means go for it.

Again, cast cranks are extremely reliable and in some cases stronger than forged. Their wear rates are unbeatable b/c they are internally dampened (balanced may not be a good word) and do not exert stringent stresses on them that a steel crank can. If you are not going to make more than 1.25 HP per cubic inch, and your funds can be diverted to improving heads or say maybe a roller cam...I would by-pass the steel crank.

Esp if it is a weekend warrior designed to kill the occasional Mustang. If you will be pounding the 1/4 religiously and doing some serious bracket racing...upgrade the bottom end. Again my .02 and I hope I am not confusing. :seeya


[Modified by topless68, 10:49 AM 1/11/2002]

 

I agree that good rods are more important than the crank, but with a four speed car, the crank takes much more punishment than an auto car. The stress of dumping the clutch and then banging gears at redline is enough to snap crankshafts, though that also depends on the amount of HP your going to make. I am running a 2bolt block, cast crank and stock rods in mine. I put out close to 400 hp at the flywheel and shift at about 6000 rpm. So far, I have not destroyed anything, but good rods and a steel crank would almost guarantee you'll keep the bottom end together regardless of how hard you beat on it. :smash: :smash: Whenever I run my car through the gears, I'm always wondering if this will be the time it blows. A few more $$ spent now will give you a piece of mind everytime you redline the motor.


[Modified by tsw71, 8:52 AM 1/11/2002]

 

Not confusing. I just read alot in the magazines and sometimes the real world contradicts it. What kind of crank do you recommend. Just the nodular iron that comes with most stock motors. I'm shooting for about 350 to 400 FT LB of torques. Probably 300 to 330 hp. But Its only a $50 or so upgrade so its probably worth it overkill or not.



[Modified by TTop Tony, 11:02 AM 1/11/2002]

 

If you're not doing a stroker motor (I assume a 350) that would do fine. Scat makes an excellent cast crank that is budgetary minded and is, what they claim to be, twice as strong as Chevy's cast-iron alloy. If you're building a 400 I would definitely check into an aftermarket Scat...that is all I have personal experience with. I do have a friend I race with and has had good success with Crower, Bill Miller and several others.

If you are bldg a crate motor, which it sounds like you are doing, your choices might be limited from your supplier/builder. If you are peace milling together there are hundreds of re-sellers of good used forged and billet cranks.

 

I have hyper pistons, GM forged crank, and lighter type I beam forged rods. Many of the manufactures give hp and rpm limits of their produces. KB pistons were 7000 rpm and the rods were rated at 500 -550 or something like that.

Always pay for a good balancing job. :seeya

 

Is he offering a steel crank for $50 more than a base price? Probably be worth it. I would still stay with eutectic pistons, esp in that HP range.

If you don't mind me asking, who is the builder and what cam do you plan using? and CID?

 

I'm talking to Jasper engines and I'm going to go with a XE262 cam. Jasper seems to have a pretty good rep. Comp Cams suggested the XE262 with my manual tranny. No idea what heads I'm using either the sportman II or performer alum.

 

I'm gonna make an edukated guess here... when a price quote between a cast & forged crank is extremely small (like $50), it usually means the crank is a "turned" or refurbished crank.. not new. Notice I said "usually". It won't hurt to ask if the crank is new, not used.

 

If it is refurbished is that really that bad?

 

we run cast cranks in our circle track motors for years at 6500 plus and only broke one....freshening up one right now(stock rules class) that turns 6800 cast crank cast pistons and stock x rods...solid lift cam .565 lift that will run all season and never come apart.ran all season before that...(i better knock on wood) :rolleyes: cast cranks are lighter too then steel spin up faster.But if your ever thinking of running nitrous or getting some serious power out of here then go forged pistons first.my 2 cents


[Modified by pats406nitrovette, 12:36 PM 1/11/2002]

 

Make sure they have crack tested it, forged cranks are notorious for cracking. Regrinding is not a concern...cranks will never break thru the main journal. Some builders regard turning a crank as increasing its strength because you are increasing the area between the journal and the crank cheek, where most cracks occur on any kind of crank.

Again, make sure the crank is crack tested. If it were me, if I had a choice b/t a new cast crank and a refurbished steel/forged unit...I'm going cast every time. I don't know what the history is on the crank...was it in papa's work truck or has it seen 200+ passes down the 1/4? Long, hard service from a past life is the unseen variable.

 

And even that is rare!


Don't say it!! I can't tell you how many times I've bragged about not burning pistons...and sure enough, every time...next pass. :lol:

 

thats why i said knock on wood ya never know when she'll blow :(


[Modified by pats406nitrovette, 1:02 PM 1/11/2002]