Pistons - Cast vs Hyperuetic Cast?

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charley3
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Pistons - Cast vs Hyperuetic Cast?

Post by charley3 »

Why does the standard Poor Man recipe specify ordinary cast pistons instead of hyperuetic pistons?

Same question for the Mild Mini-Stroker recipe.

Aren't hypereutic pistons better than ordinary cast, or are hyperuetic only better in cold climates?

I'm aware of the benefits of hyperu pistons, but is breaking hyperu pistons a concern?

I've never had a problem with the stock hyperu pistons in my 99 XJ, but I'm unsure with a stroker.
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by Cheromaniac »

Ask the guy who came up with the recipes. ;)
The original poor man's recipe specifies 677P pistons to achieve a 9.25:1 CR. None of the available hypereutectic pistons will get the CR low enough to run 89 octane fuel.
The mini-stroker recipe requires pistons that are short enough so they don't protrude far above the block deck at TDC e.g. Silvolite UEM-2229 compression height 1.585". All of the available hypereutectic pistons have a compression height of 1.592" so unless you can find a thicker head gasket, the piston to head clearance will be too small.
Hypereutectic pistons are indeed better than cast but they also need to have the right specs (compression height, dish volume) to work for certain applications.
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by charley3 »

Cheromaniac, you are the guy who came up with the recipes. I think I know who you are from Googling and reading others reply to Cheromaniac (Clark Kent) by your real name (Superman). Also, you personal Jeep specs (fingerprint) in your signature exactly match your Jeep on you website. I know it's you Dr. D.S. I've know for at least a week you're Cheromaniac.

I've read your website thoroughly, including your bio. It only took me a week to realize Cheromaniac is Doctor **** *****, antistesiologist and beloved Jeep stroker guru.

I figured posting here was asking you while at same time possibly getting others opinions. I appreciate your helpfulness and patience answering my newbie emails too. This time I posted my question in the forum because I worry I bother you to much by email.

You're an amazing man, being a medical doctor, Jeep Stroker Guru, and from Greece living in Saudi Arabia and typing perfect American English. By my count that means you know at least 3 languages very well.

I appreciate all you do.

P.S. - I'm a computer programmer and Web SEO guy. So I work in a technical profession that has nothing to do with automobiles. Yet I'm facinated with Jeep XJs, Ford Rangers, and Buick and Oldsmobile luxury cars.
Last edited by charley3 on July 10th, 2014, 11:56 am, edited 1 time in total.
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by charley3 »

Cheromaniac, how recently have you checked what's available in hyperu pistons?

Is it possible there could be a recently released new hyperu piston with specs that'd work in a mini-stroker?

I don't yet have the knowledge to look for myself.

One thing I think I understand now (from Wikipedia) is that hyperu pistons are harder, but more brittle, than ordinary cast. Is that correct?

Are hyperu pistons slightly taller to make them stronger (so they won't be too brittle)?
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by Cheromaniac »

charley3 wrote:You're an amazing man, being a medical doctor, Jeep Stroker Guru, and from Greece living in Saudi Arabia and typing perfect American English. By my count that means you know at least 3 languages very well.
Greek is my second language and I speak a little French (plus a few words from other languages), but I was born and raised in the UK so British English is my first language. :)
I had to laugh about the Clark Kent/Superman thing, and I also have a passion about Mustangs (my other car is a 2006 Mustang GT). :lol: Take a look at the bottom of the page http://www.angelfire.com/my/fan
The 4.1/4.2 mini-stroker is an entirely different kettle of fish from the 4.5-4.7 stroker. Due to the shorter (3.50") stroke of the 232 crank, the choice of connecting rod/piston combinations is limited. You have to use the 4.0L rods in a mini-stroker simply because there are no pistons that are tall enough to work with the 4.2L rods so that's easy.
The only off-the-shelf pistons that can be used with the 4.0L rods in a mini-stroker are the Silvolite UEM-2229's (compression height 1.581") and the Speed Pro 677P/677CP's (compression height 1.585"). Both are cast aluminum. The Speed Pro H802CP/H825CP and the Silvolite 3241hc/3242hc hypereutectics are a little too tall at 1.592". I don't know why they were made taller than the aforementioned cast pistons (remember OEM pistons are also cast and are 1.601" tall) but hypereutectics are indeed stronger but also more brittle. I've seen hypereutectic pistons shatter like glass in a blown up engine (thankfully not one of mine!).
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by charley3 »

P.S. - I had eye surgery yesterday. I'm still affected by the anistesia apparently. Been doing stupid things all morning. I got an emergency help needed call from work and it soon became apparent that I still can't think straight. I fumbled through the work stuff and now realize how really stupid I am today. Taking rest of day off.

===

Funny story about the work stuff. I was supposed to have today off, being day after surgery. But they had technical emergency at work they asked me to deal with this morning. I figured why not. It sure have only taken me 30 min at most to fix using my home computer connected remotely to work. I spent and hour making the emergency worse, then another 30 min and I finally fixed the problems I created :doh: and the original problem. :D (score: drugs 3, me 1) :roll: Then they kindly asked me to take the rest of the day off as I had intended to do. Well, I had warned them before I started that I didn't think I was fully sober. But I'm their only on staff tech. They should have waited till tomorrow or called my backup (a subcontractor). Oh well, that'll teach 'em! :lol:

===

Please excuse any dumb things I may have posted yesterday or today. I've been a drug addled moron yesterdat and today. I don't even fully remember what I posted earlier and don't trust myself to edit anything or reply to anythng, now that I have sobered enough to realize I'm not sober.

It took me 4 tries today to type the url correctly to get to this website. I don't know if I seem inebriated in print, but I assure you I am. Severely inebriated last night and somewhat today.

The thing is, I "think" I'm still lucid regarding strokers, but if so that's because I didn't know much to begin with. Don't know much, can't forget much. I can't remember how to do my job properly, and motor skills like typing are really difficult. You have no idea how many typos I've made and corrected just in this sentence.

I'll come back tomorrow when I'm sober.
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by charley3 »

I'm sobered up now from the anestesia. Took a day and a half.

Thanks for the answers Cheromaniac.

Hyperu are harder, but more brittle. So I don't think I'd call them stronger. The hyperu certainly have the best thermal properties.

Wikipedia says there are hyperu pistons for high performance gas engines that are less hyperu than OEM hyperu pistons, which makes the high perfprmance hyperu pistons less brittle than OEM hyperu, but still harder and superior thermal properties to ordinary cast pistons.

Those high performance hyperu pistons are the bomb diggety do dah for daily driver performance engines, especially in cold climates.

But that's irrelevant since no hyperu pistons fit Jeep strokers. Ordinary cast pistons will be good enough for me.
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by SilverXJ »

charley3 wrote: Wikipedia says there are hyperu pistons for high performance gas engines that are less hyperu than OEM hyperu pistons, which makes the high perfprmance hyperu pistons less brittle than OEM hyperu, but still harder and superior thermal properties than ordinary cast pistons.
The wikipedia article on hypereutectic pistons says no such thing. It makes references of "Performance replacement alloys" for hypereutectic alloys, the 4032 and 2618 alloys. Both are not used in cast pistons. The last line in the article also states "Aftermarket performance pistons made from the most common 4032 and 2618 alloys are typically forged." They say typically, but I have never seen a cast piston using either alloy.

As was stated in your last thread and from wiki; "hypereutectic pistons commonly use a level of silicon between 16% and 19%." Below that level is considered eutectic.

There is no "performance" hypereutectic alloy that is "less" hypereutectic
Those high performance hyperu pistons are the bomb diggety do dah for daily driver performance engines, especially in cold climates.
except they don't exist.
But that's irrelevant since no hyperu pistons fit Jeep strokers. Ordinary cast pistons will be good enough for me.
There are several hypereutectic pistons available for the 4.0L and stroker engines. Go read the FAQ on available pistons. Hypereutectic pistons are also cast pistons. Hypereutectic refers to the material the piston is made out of and cast refers to the method in which the piston is made.
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by charley3 »

Silver XJ...

Maybe it wasn't Wiki where I read that. Maybe it was at Summit. I don't recall. I thought I read it somewhere. Maybe it was the drugs.

Surgery this week blurred my thoughts and memory, but it's coming back to me now. I think Dino meant no hyper-u pistons for long rod strokers. I was hoping to build a long rod with hyper-u.
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Re: Pistons - Cast vs Hyperuetic Cast?

Post by Cheromaniac »

charley3 wrote:I think Dino meant no hyper-u pistons for long rod strokers.
Correct.
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