US1 Fountain

iTrader: (1)

Make sure the top ring is properly gapped for the hyper pistons, otherwise you will have 2 pistons in each cylinder.

Hydrocruiser

Why is it that most mechanics are ok with Hyper pistons that are factory installed but prefer forged if they are doing the rebuilding?

f311fr1

AZ Speed & Marine 600 HP 496 engine replaces the GM crank, rods, and pistons in a NA engine. Raylar's higher HP kits also offer forged pistons. Joe Murray

Hydrocruiser

I always wondered why GM missed it's day in the sun with the 496's. Maybe they will get smart and re-introduce back the 502's. Seems like a lot of GM's management has been off base and the Company is on the rocks on Wallstreet. Too much old wood ideas and a centralized decision making pool that has to approve everything...the company just got to big and stale for it's own good.

Whiteknuckle

I had hypernuetics in an engine for about 5 yrs. The last time it was on the dyno it was at 440HP. We just pulled them out to also make some other changes and they are in excellent condition. However, I agree, that if you are going over 500 HP you should go with forged just for the insurance. My hypers were Zollners, an old name in the OEM business. I keep saying this, but modern cast parts are much, much better that the stuff made in the 60's. Metallergy and machining have come a long way.

blue thunder

I run the KB hpers and have not had a prob at just under 500hp per engine. I like the thermal stability and lightness and I believe more power from them. As always I agree with everything whiteknuckles already said.

I added .0005 on the bore over automotive but I do run closed cooling. Top ring gap set to .034 which seems high, but that is the recommendation due to the high positioning of the top ring.

BT

BGIII

iTrader: (3)

I would use forged. I will never use hypereutectic again. Had one break at about 30 hours. Lucky for me it was about 2 hours after I had sold it.

hillbilly24

What it all breaks down to is, Hypers are good pistons for the right application and when setup properly. If your builder is recommending them then they are probably the right part for your situation.

Raylar

Some thoughts on hypereutectic pistons. In the "old" days the only choices for pistons were straight cast (pretty weak parts) and forged( stronger but crude by todays forged piston technology.) The manufacturers, who fund most engine part development, needed stronger inexpensive pistons that would take the extra heat of the emerging smog motor technology. The hypereutectic piston was developed and it is basically a cast piston that has a silicone additives in the aluminum to make the aluminum harder and hence stronger, and oh ya more brittle. The car manufacturers also wanted pistons that could hold tighter clearances to the bore. This tighter clearance requires a carefully machined exterior that needed a harder material to hold the overall growth of the piston to a minimum and with the subsequent tighter tolerances and clearances the motor would also be quieter and would be more emissions friendly. These hypereutectic pistons were never specifically designed until recently for high performance and marine use. The forged piston has always been a stronger piston but it has a tendency to "grow" more than a cast piston when hot . This growth neccessitates larger clearances in the piston to bore fit and hence is noisier and is not compatible for todays emission motors especially when the manufacturers "bean counters" look at the cost differences. Todays hypereutectic pistons produced by companies like Mahle, KB and others are high quality pistons with greatly improved designs and construction and will support horsepowers of well over 500HP when they are carefully applied and installed. The problem with hypereutectics come when they are subjected to high compression from supercharging and detonation. Todays forged pistons are also much better than earlier forged pistons in both design, construction and alloys. Obviously, we know the 496 -8.1L motor pretty well and I can tell you in a normally aspirated use the hypereutectic pistons in this motor can take 525 to 550HP quite well and they only become overstressed when they are subjected to supercharging, bad fuel with detonation and if they are pushed above 550+HP levels. If you are going to purchase new pistons for high performance marine use I would definitly recommend spending the extra dollars for a quality set of forged pistons. If your motor has hypereutectic pistons like the stock 496's, stay away from supercharging, turbocharging and "rot gut gas" and your motor will most likely have a nice long life. Just some added information- schools out!

Ray @ Raylar

Kokopelli

Thanks Professor Raylar!!!!