blue thunder

Those are my thoughts exacly raylar on hyper pistons as well as todays nodular steel cast cranks. When setup and use is correct, they are a great choice. Forge basically provides a margin of error in 500hp and under engines guarding against setup/use problems, but there are trade offs. Cost is but one of them. To this day I cannot figure out what most marine perfomance guys have against these parts other than falling prey to "group think". Yes, I know there are failures with hypers, but there are with all types of parts. One must completely understand the failure mode of a piston coming apart to reject its manufacture method as faulty. Most failures if drilled down to root cause will be shown to be setup or use related.

Now what was the topic again....

BT

samracer

ok hyper pistons are good for 600 hp, if you buy good ones
but forged will hold more, but you have to leave more room for them in the cylinders, but that wont matter because you wont be starting this motor daily

i would go with forged only because if something goes wrong, you are more likely to be able to save your motor with the forged because they will melt a whole through it unlike breaking into a billion pieces like most hyper or cast pistons would do

articfriends

iTrader: (1)

When i had a set of hypers fail they were set-up 1/2 thou looser than what gm set them up at in a gm crate zz4 ho, 2 of them broke where skirt attaches to piston below the oil ring land,i blame it on the lack of attachement and support from skirt to piston top. Most hypers you look at have nothing supporting skirt from piston pin boss to the other piston pin boss. The motor started rattling funny and believe this,i tore it down BEFORE it lunched and took block out. The skirts were literally riding up and down in the bores held in by the cracks and fell apart as i pulled the pistons out. I would blame hyper pistons failing on rpm's from side loading not necessarily hp but rpm's. I turned this small block 5600 rpm's,i have turned alot of small blocks with bone stock cast piston's higher than that without pistons breaking,i guess if a guy was going to use them in a big block marine engine for whatever advantage they are using them for(saving money or tight clearences would be ONLY advantage) i would keep the rpm's low and look for any piston that had something supporting the skirt every 90 degrees. Todays forged pistons,even the cheap ones,have a high silcone level in the aluminum allowing you to run less clearence than old school forged racing pistons that had to run at clearences that didn't lend themselves to long ring life/piston sealing etc.
As far as "group think",more than one person on this board (including myself)has had a hyper piston break,quite often destroying the motor. You don't hear about forged pistons falling apart in stock,lighlty modified and even heavily modified non-race pleasure craft,Smitty

NOBODY

Just facts-------------------------------
I have pulled down many motors with broken skirts with forged and hyper pistons in the manner you described. This is a timing or clearance issue, not a material issue.
I have even seen a motor with 30 over pistons in a 40 over block with every( JE forged piston) skirts broken, this motor came in to be freshened, and let me add the owner claimed it never smoked. This was a 500 HP RR engine and it lasted all season.
I've even had a customer with a 9 sec. mustang running a factory lightning 351 shortblock on 200 HP NOS that he ran for 1 full season. I kept telling him his day's were numbered, but when we pulled it apart the pistons were perfect. He now runs all the high dollar stuff and turns the same times. The forged stuff didn't make it run faster, but will it live longer? Who knows?
Bottom line--- forged when you can afford it, hyper when you can't, and if it's not built or tuned properly it didn't matter anyway.

tomcat

"Bottom line--- forged when you can afford it, hyper when you can't, and if it's not built or tuned properly it didn't matter anyway."

That's our man NOBODY...straight to the heart of the matter.

The factory spends a lot of time and money developing an engine package for a given performance range. When we come along and change things to make more power, we may take a lot of components outside of their envelope, and even if you upgrade these parts, the specs for building and tuning change. I remember an article about Lingenfelter discussing how much work it was to get the ASA spec engine program right. This is the true value of a real engine builder.

NOBODY

Just want to point something out----------------
I have had a total of 5 boat motors come to me within the last year with motors ranging from 468 to 540 with forged and hyper pistons, all the motors had #2 hole with no or low compression. All the motors (3) with forged pistons had melted pistons and the other (2) motors with hyper pistons had burnt valves. The hyper pistons have the ability to disapate the heat better than the forged because they are less dense. Out of the 5 engines 2 had dual plane manifolds the rest had single plane manifolds.
All these guys have the same story (they had no problems with these motors until the held it wide open for longer than they normally do). All these engines were carbed and all these engines had non modified marine carbs on them. Most carbs are calibrated for a wide open A/F ratio of 13/1. This is fine on making good power, but for a boat motor to run wide open for a long duration this is a recipe for disaster.
The moral of the story---If it's your first time building a boat motor make sure you check your A/F ratio with a wide band O/2 sensor or check the plug the proper way to get a wide open reading. This is not done by running your boat hard and idling to your dock to then pull the plug, this is done by running the boat wide open then clicking it off at max RPM, then pull the plug. I would always check the #2 plug first because this is the leanest running hole on standard BB chevy heads.
If you ever get a chance to pull a plug on a 500 HP or something from the factory that makes good power you will notice the plug is awful dark. Most engine guys would say this is too fat but mercury understands this is what it takes to survive in the marine world. Having a carb that is fat at an idle or cruise is not what i'm talking about, It only needs to be fat when you are at WOT. I believe this needs to be at least 12/1 or lower. Don't end up like these guys( having someone good at building motors only to have it tuned wrong costs you time and money).
Just because you buy a Marine carb doesn't mean it's calibrated for your engine.

QUIKDECISION

I want to thank you all for your valuable input. I have chosen Forged pistons. I am comfortable with this since it was what was in the engine to begin with, and from what I have read thus far, the extra $$$$ are worth the reliability. My son and I are doing the rebuild. ( Dad and Lad ) THe wild enthusiasm is wearing off a bit. I would not look look forward to having to do this again for awhile.
Doug

formula31

Oh, dont ever say anything like that, it will jinx you for sure.