i just tore apart a 283 for rebuilding and found that it was already bored .030 with new pistons. what baffles me that all pistons except the one shown had broken top ring...some were broke in more than one place. i know that hypereutectic pistons need more ring gap and maybe that is what was going on here? i've never messed with them, these look like plain old cast to me. i'd like to reuse them if possible as the bore is only wore about .003 the only number on them is 1544 166 and google came up with nothing. i see that Keith black has KB166 pistons for a 283 , but they are domed..these are flat top with 4 valve reliefs any help? are these useable or junk?
Hypereutectic simply means that there is more silicon in the aluminum alloy than what is soluble in the aluminum at the operating temp. Because of this, the hypereutectic pistons have a much lower coefficient of thermal expansion, which means you can run tighter tolerances and clearances. Hypereutectic pistons are normally cast, not forged. However, there is no garage method that I am aware of to tell the two apart. Good Luck.
Was the ring broken, or the top ring land broken ? Broken rings can be from detonation, and/or age. As you suggest, broken ring lands are common with Hyper' pistons running too small a ring gap. KB gives the correct ring gap info on their site.
top rings broke on 7 pistons....the pistons are fine i guess i heard you need more gap on hypereutectic pistons, but i wouldn't know one if it walked up and bit me. so i was thinking that may have been the problem. any way of telling if these pistons are or not?
36, K-B Hyper pistons should all be machined for full floating pins, meaning there will be a groove on each end of the piston pin bore. You will have to remove a piston pin to verify this. A good engine machinist can check these old pistons and tell you better if they can be reused. To speculate without seeing them in person, and micing them would be pure speculation.
With the 1 top ring that is left intact, you can place it just under the ridge in a clean cylinder bore, and try an measure the end gap. I am assuming there is a ridge at the top of the cylinders and that's why it would be hard to do it there. That is if you can remove it without braking it, I would guess probably not the way the other 7 are broken. There is more to your story friend, as that pin looks real nasty from the picture.
Looking through the KB catalog, I don't believe that to be a Hyper KB piston. The Silvo-Lite series should have coated skirts so that rules that out for the most part. It looks like a stocker to me, and I don't ever claim to be a stock engine expert.
thanks for the info. i think you are right when you say there is more to the story...looking at them now all the pins look like that. just measured the crank that had .010 bearings on the rods and mains and found the rod journals fine , but the mains were WAY under and grooved i think someone put some serious hurt on this motor..the guy i bought it from said it ran fine until it started running bad. so much for a quick rings and bearings job
36, there is a good chance also the pins have that appearance because of the broken top or compression rings. Combustion pressure is not being kept above the piston but actually passing down past the rings because the second ring alone is not enough to handle the pressures by itself. Hence you are getting a sooty appearance on the outside edge of the pins and piston pin bore sides.
First thing I noticed was the pin area of the piston also; is it loose or just how it looks? Do the pistons have the steel re-inforcing struts/plates supporting the inside, pin area of the piston? If they do, they are just a normal, cast, rebuilder type piston. At an attempt at humor, drop a piston on concrete, if it shatters, it's hyereutectic; if it just breaks or dents, it's just a normal cast piston. Glass contains silicon, and shatters also, as an anology. I don't think your pistons are hyperutectic; they don't look as well "finish machined" as most hypers are. This thread is somewhat "odd" to me, as I just gave away a.030 over, complete rotating assembly to a fellow HAMBER yesterday for a ............283. And, on tearing that short block down (just to use the block), number 7 and 8 pistons both had the top compression rings broken, but no obvious reason for it. About the only thing I could think of was, was the top ring slamming into the cylinder ridge due to excessive bearing or pin clearance? Butch/56sedandelivery.
You can tell a piston is hypereutectic because sooner or later it will be all over the bottom of the oil pan. It was a genius of marketing who was able to convince people that they are a "performance" piston. A piston is hit with a sledge hammer every time a spark plug fires. The higher the compression the bigger the hammer. Why people have made the choice to cut cost on an engine with these pistons is beyond me. Probably not much help on your question, just like to bash the hypereutectic craze whenever I can.
Hmm, I have 100k on a hyper kb piston set, none in the bottom of the pan .. likewise i built a motor for my son 355 sbc at 90k oil pressure was getting low so tore it down turned crank , new bearings honed and re-ring went back with the hyper pistons that had 90 k , sold that vehicle at 125 k and he is still driving it.. Never heard of anyone having problems with them.
Glass contains Silica, not Silicone. Entirely different. Silicone is added to Aluminum, to reduce the expansion. Tighter clearances, less noise, especially at start up. The down side, is it doesn't transfer heat as well. So the top ring gap needs to be bigger. Their "bad" reputation, comes from people who can't/won't follow the instructions. And people repeating bullshit.
the ring end gap was probably to tight and thats why the broken rings. i dont really believe the piston type has much to do with what the ring gap should be, a ring gap should be what the manufacturers says its should be. Hyperutectic pistons bore clearance was one and a half to 3 thou, generally a .030 piston actually only measured .0285 oversized, so the correct clearance was built into the piston so you basically bored the block .030 and it was right on. but i always checked em anyways and i always ran the clearance at about 2 thou. so if you said the bore was wore 3 thou you acutally have something like 5 thou of clearances, which is really only 2 over the max they say. There alot of motor guys that would tell you to bore it, it will work and run fine, ive patched together motor for guys that had ten thou clearance and they ran beautiful! Id also just probably polish off the crank and slap a set of bearings in, you could probably have the crank turned to .020 but it probably wont really gain you that much just take another 100 out of your pocket. my 2 cents
I'm about 110k on mine with about 10:1 compression and tons of thrashing on mine with no problems at all...
Hyper pistons ARE cast pistons. There is no difference in how they are made, only in the composition of the alloy. Not all of the KB pistons are marked for the front. We just got a set in for a 392. They are not marked. But then, they are 100% symmetrical.
I've seen top rings broke like that in a motor that was reringed when it should have been bored. It had a bad ring groove in the top of the cylinders that was not cut out before installing the new rings on the old pistons.
I think if you'll look up Silica/Silicon/Silicone, you'll find they're ALL "inter-related", and are added to various items to make that item more heat resistant, durable, make the item smoother, and harder. As far as Keith Black pistons goes, it's because the top ring is closer to the piston top, thereby exposing the ring to higher heat; the ring gap is increased because of expansion to the ring itself, not the piston. Part of the theory, is to help build heat in the piston top, thereby creating more horsepower (KB); it's also gotten KB a bad rap due to piston heads "popping off", or breaking the top ring land because instructions are'nt followed precisely. Other manufacturers don't address it the same way (Speed Pro), they don't move the top ring higher on the piston, and don't have the problem KB seems to have. Hyperutectic pistons are far more sensitive to detonation that, among other things such as dropping, causes them to shatter. Many new car manufacturers have gone with hypereutectic pistons, but with them, timing is computer controlled, in part to sense detonation and retard timing; something older engines, such as a 283, don't have working for them. The piston manufacturers build what sells; and later model engines are what "most" people work with. I suppose it's also cheaper to use only one "casting" technique now-a-days for cost containment purposes. I think the OP's problem is related to some clearance issue; ring gap, piston to bore clearance being too tight, excessive bearing clearances (he did say the mains were out of spec), or cylinder ring ridge not being addressed when the engine was rebuilt. I still don't think his pistons are hypers, but who knows for sure; to me they look like a standard, cast aluminum, rebuilder type piston, and probably made by KB, or by KB for another vendor. Personally, I don't care for KB pistons. I have a nephew who worked for KB in Nevada, and has some negative things to say about the company and it's produsts; when an employee badmouths their employer, there is usually some truth to it. Speed Pro moving offshore to India is already hurting them in the quality of their product. Butch/56sedandelivery.
You guy's that bash Hyper pistons are rediculous, they are telling you something- STAY THE HELL OUT OF REBUILDING ENGINES!!!!!, and leave it to people who know what the hell they are doing. Some of the dumbest comments I ever heard in my life every time the subject comes up.
to the op.those pistons look just like the ones i took out of a 283 last yr. and with 4 top rings busted. all on one side.to the rest that are runnin down hyper s, well ive used them for awhile now and i learned to read many yrs ago,so i follow instructions. and i hammer on ALL my engines.ive never had a problem with them yet.the engin e in my ranchwagon ,a 383 chevy has hit 8000 rpm alot of times and it still here.now for how long i cant tell ya but so far so good!
Just use Forged Pistons, end of problem!! or like my Cummins ISX, it has Forged Steel pistons!! never have to look at the pyrometer again!!! Chris
Look in the inside of the pistons EVERYWHERE. There's a part number in there somewhere. If it's a Silvolite, for example, it will have a four digit part number, that SHOULD start with a 14.
...and/or a trademark. logo, or name of the manufacturer. Years ago I was shown a piston that an aftermarket tractor engine parts manufacturer had duplicated in China. They did such a good job that the 2000 pistons he had ordered all had the trade mark of the manufacturer of the original piston perfectly duplicated as well.
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