Hypereutectic VS. Forged pistons

[CJguy]

Got this question asked of me and my response, would like some opinions...

Qeustion:
I was looking over the specs on your build and please do not take offense but why did you decide to go with Hyperutectic pistons? I have just recently read of a bunch of failures with them, melting and cracking on the Cleveland forum. Some have had absolutely no problems and others have had major problems. Some are to be expected because of Boosted applications, but others have been in mild street engines. I actually had a set of Hypers on order and changed it to the TRW Power Forged for this reason. I am hopefully going to get my machine work done soon after the pistons get here. I do not want to scare you and I know you know what you are doing but I just wondered why you went with Hypers instead of a forged piston?

Response:
Ya know I am glad you asked at least someone looks. And no offense taken and let me explain why some Cleveland engines fail. I could write a whole book on this subject. The Cleveland as you know is a thin wall block, ok having said that, my main priority on finding a block to build was it had to be a standard bore with XXX's. The reason is, the cylinders move esp. on an overbore and I needed one that had not been used and abused.

The biggest problem with folks building a Cleveland is they don't understand the block and more times than not they overbore an already marginal block. What I mean by that is that the cylinders have moved and when it is bored the walls could be of a different thickness within the same cylinder. Which causes temperature variations and weak points. The only way to verify the integrity and uniform thickness of the cylinder wall is with a sonic check. I had my block tested prior to the re-bore of .020 and tested way beyond expectations, almost perfect. It could have cleaned up with .010 but due to the availability of pistons, went with .020 over.

I was going to use forged pistons up until I had my block sonic checked. The block had no issues and already had the screw in plugs, which further increased the stability of the cylinders. So the benefits of the hypereutectic pistons far outweighed
the use of forged pistons. Also, in my application, “BowTie Killer street machine”, I won’t be taking it to the track or pumping out 500+HP, but will run at 6000rpm all day long.

I suppose the problem that folks have with hypereutectic pistons and failures is the lack of understanding and block prep. Hypereutectic pistons are in many ways far superior to forged with regards to the piston dynamics. If the block is marginal as I explained above, I could understand why one could fail, melt, crack, ect. at high output/revs. Whereas the forged pistons would only show excessive wear on the both the cylinder and piston.
I hope I explained as to why I don't need forged pistons and I hope you had your block checked and didn't go past .030, just the way of a Cleveland...

[MOKANRACER]

I have heard con,s/pros about these pistons since they hit the mkt. A few of my fellow racers have had bad luck using them in their application. A lot of Budget CRATE mtrs come with these pistons. I use these in my (388) 55 Chevy mtr with a 100 shot. The shop that did my machine work wouldnt install them in my short block,untill they had a few conference calls with the manufacture as to bore to piston to ring clearance,s. I would never use them in a purpose built race mtr, but have had no problems in my 55 Chevy application. They certainly arnt designed to take the pressures of a Nitrious or high pressure race mtr, but are certainly stronger than a lot of stock mtr pistons,due to the high silicon content. This is just what I have learned .Just another point of light for you guys.

[72Chero]

:eek: :eek: as you know, I run them in RED....GROUCH has them too, 6 years on that rebuild and grouch is still strong...:D :D

[oneowner73]

I almost ran a set of hypereutectic pistons too long. They were in a small block Chevy 355". Ran it a long time shifting at 7400 in a drag car. Changed cylinder heads and felt like I was short shifting. Bumped the shift up to 7800 and knocked off another .02 and added .5 mph. Only ran about 25 to 30 runs at that rpm. Last pass of the season the car slowed in the second round from a 6.465 to a 6.55 for no apparent reason. I knew it had to come apart. Found chunks missing from the #4 skirt and a crack going into the wrist pin hole. Too close for comfort. New motor will be forged pistons for sure. Didn't start out to be that high an rpm engine. So the moral of this story is that if you think you might add better parts or nitrous or a blower you might as well build it right the first time. I just plain got lucky to be able to use most of my good parts in my next engine.
Brian

[CJguy]

Glad you caught it in time. I have always said "your application is what dictates your build". If I was going to build a race engine with bolt on boost, no question, forged...