I was thinking 8.5:1 Bill with open chamber edelbrock heads. Pistons are down .010 in the hole. Right now I have 9.5:1 with kb201 pistons. And thanks for the refresh on piston fits, its been three years since I built an engine, it a little foggy.

These are 454s fastlane.

Yeah got it.The reference to the 496's was for pistons.You have Gen iv's,v's or vi's.Mate personally i would say don't do it.For the gain you will make- 70hp.Remember the 525SC was 7.5:1 compression and there was a reason for that.To make them live.The 177 blowers are much to small for even a 454.I had a set on 2 x 454 mags.Low hour motors with forged internals.1st motor lasted 10 min.Why you may ask-purely set up.Then got new 502's same 177's.all these little blowers will do is spin there heads off,heating the air in the process and with 9.5 comp you are going to cause yourself lots of troubles for very little gain.Sorry if i seem so negative but a blower motor is built around the blower.I talk from experience,ask me anything you like but if you enjoy boating leave your motors as they are or have proper motors built to suit blowers.

My engines are close to built for blowers, all but the pistons. Everything else would be good. I'd think a "little" blower would be well applied to a higher static compression engine. That's one with forged pistons I guess. I contacted a rep for KB pistons. He says these pistons are designed for super charging. You guys in the real world say different. I was curious why they would call out ring gaps for marine super charged applications if they were not meant for such an application. I have yet to hear of a success story when using hypereutectic pistons in a blown application. That's pretty compelling evidence so far. Plus I almost have my mind talked into refresh with forged pistons this winter. That is if I could find some .070 over. Any luck today BillK?

Arias makes custom pistons. I think they were only $100 over off theshelf pistons when I ordered a few years ago.
BTW, they also have a lot of experience with blower motor pistons.
http://www.ariaspistons.com/

If you do a ceramic thermal-barrier coating on the piston dome and chamber, you'll solve most if not all of your heat problems. Do a thermal ablative on the bottom side and that will also help shed some of the heat thru oil splash. PM me if you need details or sources.

I don't think I have ever seen a supercharged engine with cast pistons, even from the penny pinching automotive OEMs. I think there is a reason for that.

Michael

JE/SRP has all kinds of 4.320 pistons. If you want off the shelf their is the forged SRP in many different dome style. I just replaced my JE closed chamber 4.320"s with SRP open chamber 4.320"s. Kind of a bastard size bore. They SRP's run around $540

http://www.jepistons.com/

I've been reading this thread and thinking to myself " I just wouldn't do it ". I'm a firm believer of doing it right the first time. It ALWAYS ends up costing less, in both time and money. Just bite the bullet and purchase the fordged pistons. You'll be much happier in the long run.


Darrell.

Ok.....I'm not a supercharged guy, but my recommendation would be forged without question. Throw the block out or get one-off forged pistons made....but stay away from hyper-u-cracked-it. I did some search on this website about hypereutectics and posted messages..and found the hyper-u-cracked-it deal. The reality is they are extremely brittle alloy. Forged pistons are tough pistons...not brittle. Here was my scenario..

I ran the motors WOT..hear some clanking in the one motor, then backed off. Well, my boat did not get on plane with one motor so I decided to run the hurt motor. Seconds later, it clanked...then pop...bunch of steam and all is over. Now I'm down to one motor with a cooler filled with beer..no problem. The failure mode of the hyper was miserable. Yes, I lost a rod end bearing from lack of lubrication...but the hypereutectic exploded causing debris to spread through the rest of the engine bending valves and sticking a rod through the cylinder wall. If I ran with a forged piston, it would have been in meltdown in a less severe mode. I kick myself saving a couple hundred of bucks on pistons because it cost me thousands in repairs. Regardless if you run boost or NA, run forged pistons. It is a no brainer when you think of the failure modes and resultant damage. A forged piston will not explode like a hypereutectic. I have a ziploc bag filled with piston parts as a reminder to purchase forged for as long as I own a boat. Having some oil in the sump would help too...but we all know, goofy stuff can happen....leaky riser contaminating the oil, leak oil hose, deto....a few hundred bucks more is a cheap insurance policy on a looming engine failure whether it'd be 5 hours or 2000 hours. Don't build cheap in the marine world!!!

.034 is way too wide. I have high boost pressure marine engines that I run ring end gaps alot tighter. If you want a sealed engine for along time .034 is not where you want to be. Hope this helps.Also the JE piston suggestion is a must!