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Cast or hyperutectic pistons

8K views 36 replies 14 participants last post by  just another car guy 
#1 ·
The engine im building is a 383 that will be street driven with a few track trips if any. I am looking at around 475 hp and about 475 ft. lbs of torque. Compression is going to be around 9.5 - 10. A few people have said i will be fine running cast pistons, others have said run hypers, and the auto store told me run forged. I am not going to run nitrous so i don't need forged right? So will cast be good enough or should i go with hypers? The engine will not see over 5500 rpms.
 
#2 ·
You prob. would be fine running cast but I will say go with hypers. Since it looks like this is not going to be used on the strip that much given not going over 5500 I think you will be ok as long as everything is set up well.
Forged would just be added weight to your rotating assem. that given the use you won't need esp. not running nitrous.
Hyper is kinda the hybrid tech. out there and most people say they are ok and many people have used them now many from this site as well.
So for your use hypers will take the beating better then cast but since you don't need what forged offers why not just go with the middle man and get hypers?
Like anything the better your engine is set up the better and safer you will be if you go into denotation you can kill any kind of pistons really quick. Your compression is normal for street so you will be safe with hypers.

Thats just my .02.

Chris
 
#3 ·
You can run either and it`ll be fine. If you want a decent hyper piston at a good price check out dirt track thunder, look at the Speed Pro piston line, make sure you get the jobs with the coated skirts, as usually the non coated skirt jobs have .020 off the tops and there not going to tell you this. I don`t know if you plan on using 5.565 400 rods or the 5.703 350 rods, either way the same applies piston wise.
 
#4 ·
Good ideas from both.The Hyperutectic pistons will work fine. We put some KB .030 in my Brothers car and they are in good shape in abox downstairs. The pistons did not fail,just the Mexican block. He switched sides and went to the Blue Oval team,so I got 8 KB's with 2200 miles on them, for free just a little clean,good as new.
 
#8 ·
I would not recommend that.You may have got lucky,but one bad shot of nitrous and the weakest link goes first,even if it is not a bad to do any other damage,cast will break easily. If you are going to build an engine and plan on spraying it be smart and get the parts that are more willing to stay togather.
 
#11 ·
noisy forged?

I am running forged. In a 355 sbc rev to 7500RPM. 11.2 compression, alum. heads. I would go forged on any build. Then later down the line I can do what I want. Just not worth the difference when the engine is already down. I have never had piston slap with proper clearance on forged. But I do fit each piston to the bore by fine honing. I also would never use the 5.35 400 rods, too much side thrust. Go with forged and good rods.
Hypers have a high silcone content. Some are not machined to well, the silcone hinders the machine process.
 
#13 ·
uh other than cost forged used to have the stigma of increased ring wear due to the fact that they have more expansion than cast pistons. Or like lluc said, they're a little noisy slapping around until they get warmed up. Most people like to buy forged pistions because its a good "upgrade" but I really wouldn't use them unless you really need them.

My old chevel had cast pistons and shifted at 7,500 RPM with a 355 it was my daily driver for 2 years.
I seriously doubt that. Most ignitions won't make it up that far, let alone stock internal parts (which correct me if I'm wrong, is what I'm pretty sure you're alluding to). This statement is misleading, anecdotal, and generally unhelpful.

I am looking at around 475 hp and about 475 ft. lbs of torque. Compression is going to be around 9.5 - 10.
Mind if I ask how you plan on doing that? Its certainly not an unreachable goal by any means, but to make that power you're either A: going to have to use a big cam and some OK heads and spin up high which means dumping money into internals, or you can (preferably) B: dump a generous amount of money into heads and induction. With anything short of a CNC set of heads, you're in roller cam territory. You're talking about a 3-5000 dollar mill here if you start from scratch.

K
 
#14 ·
That was just a guesstimate going off of desktop dyno. which said m going to have 500hp but i dont think it wil be anywhere near that.

385 ci
balanced rotating assembly
Dart iron eagle heads
200cc intake, 72 cc chambers
Edelbrock Air gap intake
Edelbrock Performer rpm cam kit
234*/244* @.050 .488"/.510" lift
750 CFM MIghty Demon



Anybody have a better guesstimate?
 
#19 ·
hype or dislexic pistons

Hyper jerk pistons are cast, i repeat, cast pistons with a teflon type coating that wears off as soon as the piston starts scraping on the cylinder wall. If I am going to buy a cast piston. I will buy a cast piston. I am not paying more because it has black paint on the side of it. I use SCAT forged rods and SRP forged pistons in all my builds. They don't make noise.
Anybody have a better guesstimate?
400 hp

I built a 400 sb with 70 cc Edel heads and a .500 Crane cam. I got 439 realistic hp.

PS: You should be running a 700 cfm Carb.
 
#22 ·
To add to that, hypereutectics are cast but they have a silicon content of more that 12%. the added silicon makes them harder and more wear resistant than common cast pistons. Some say that the harder hypers are also more brittle although, I have had no breakage problems with them. I have heard of people having problems with keith blacks breaking in the ring land and needing larger ring end gaps, but I use speed-pros and have nothing but good things to say about them.

P.S. The paint or coating on some of the hyper pistons is a scuff coating and has nothing to do with whether a piston is hypereutectic or not. Although I do use the coated, I feel that they do help on dry starts ups, etc..
 
#25 ·
475 HP with Performer RPM Cam?

bracketeer said:
I built a 400 sb with 70 cc Edel heads and a .500 Crane cam. I got 439 realistic hp.
I do not think you can acheive that level of HP with the Performer RPM cam on a 385. I was faxed a dyno sheet many years ago when Edelbrock was testing the Pro-Flo on a 383. They made about 445 HP with the Pro-Flo (ten more than with the 750 carb), and 600 HP with a 150 shot.

Now maybe the Iron Eagle heads will get you closer to the 475 mark, but I think 440-450 HP is a more realistic number for that particular cam. With the Iron Eagle heads and a cam that is more like 240* @ 0.050 intake duration would be a better chance for the 475 HP mark.

Ed www.edgesz28.com
 
#26 ·
metal content

they have a silicon content of more that 12%. the added silicon makes them harder and more wear resistant than common cast pistons.
Yes. They are made of a different metal and are casted slightly different.

But the cost difference between them and a forged are minimal.

Some of the cheaper forged pistons are heavier but any good quality forged piston such as JE or SRP are actually lighter.
 
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