KB pistons BREAK IN HALF???

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Yes I was looking at their installation instructions. It shows the top ring should be .0065 inch per inch of bore. They also mention the second ring too at .004 inch per inch of bore. I guess I'll be pulling the motor back out and tear into it to see what the ring gap is..

I can't believe you put an engine together without checking the ring gap. Any engine build this is done.

Yeah, no doubt! Whether the rings are file-fits or not, always always always check your ring gaps! And in the case of the KBs, don't be stingy with the gap on that top ring. The other guy was right, give it a good .028" gap. I do on 440s as well as the 360s though it's on the big side on the 360. So what. It works for me time and time again. And like the others said, knowing the proper parts for the application is absolutely critical and that not just goes for the customer, but the builder too.

Posted By: gdonovan

Re: KB pistons BREAK IN HALF??? - 05/12/10 08:17 PM

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In a turbo application you're not supposed to use a hypereutectic piston anyway regardless of who manufactures it, and I was told that by representatives from two different piston companies.

Which doesn't change the fact there are companies making them for factory turbo applications.

Turbo or supercharged or nitrous will reduce hyperutectic pistons to junk quick.

Factory cast are better or forged, I have put 30 psi of boost to factory chrylser pistons and they live.

Posted By: maundmotorworks

Re: KB pistons BREAK IN HALF??? - 05/12/10 08:24 PM

Yeah, I know they still make them for turbo applications anyway despite that they wouldn't hold up well. Forged is indeed the way to go since they hold up in pretty much any application. And I think you're right on another account--a cast piston is a tough S.O.B! Look at what the drag guys used to do with cast pistons before the forged stuff came available, and that was even severe punishment for forged pistons.

Posted By: Charger_440

Re: KB pistons BREAK IN HALF??? - 05/12/10 08:37 PM

my build is not a boosted build. its a LA 360, stock build except cam and pistons. adn ported heads. so, anybody wth an NA build that has actually had this problem? both of these guys work predominantly with race engines, so maybe a street engine they'd be ok? i hadnt heard ths before now, but for 2 ppl in 2 weeks to say it...scared me.

Posted By: MoparforLife

Re: KB pistons BREAK IN HALF??? - 05/12/10 08:55 PM

Have seen many KB pistons and about the only ones I have seen that break are not installed properly.FOLLOW the directions. Mine have seen many seasons.

Posted By: DennisH

Re: KB pistons BREAK IN HALF??? - 05/12/10 08:56 PM

Got em in the BB. No problems after 6 years of misuse. My builder is well known.

Posted By: can.al

Re: KB pistons BREAK IN HALF??? - 05/12/10 09:02 PM

..even though most on Moparts recomend these pistons,i also know builders that refuse to use them.

Posted By: ramrod

Re: KB pistons BREAK IN HALF??? - 05/12/10 09:44 PM

I run KB hypers in my drag car. 360 with cast crank and stock connecting rods. I shift at 7K and the engine has seen 8K a time or two. MANY HUNDREDS of passes with no problem. Pay attention to the top ring gap and you will be fine.

Posted By: Charger_440

Re: KB pistons BREAK IN HALF??? - 05/12/10 10:21 PM

thanks for easin my mind fellas

Posted By: toplescuda

Re: KB pistons BREAK IN HALF??? - 05/12/10 10:38 PM

just how are they breaking? are they splitting down the middle? or halfway up? or if its splitting down the the middle the rings are not gonna cause a split it would more then likely from having prosity problem(something your not gonna see unless you x ray it(and im sure you guys didnt lol) iv made over 100,000 pistons working for briggs (yes there cast but not hand poured) and have seen my share of problems installing the rings wrong may cause some problems but spliting a piston prob wont be one of them

Posted By: Charger_440

Re: KB pistons BREAK IN HALF??? - 05/13/10 12:21 AM

any suggestion on rings to use? he said hastings rings are like "a bore in a box" he tells me to use speedpro seal power moly rings. any input there? i want something with a long life to it. the originals in my 318 lasted 264k mi before i rebuilt it, i want something thats gonna be there for the long haul, not smoke after 65k mi.

thanks guys

Posted By: toplescuda

Re: KB pistons BREAK IN HALF??? - 05/13/10 12:37 AM

id like to see a pic of the piston the o p said was cracked right down the middle

Posted By: 383man

383man - 05/13/10 02:35 AM

I have KB pistons running in 3 engines and all have worked fine. My 63 and my sons Dart have had them for years with many street miles and a few trips to the track every year. Also have a set in my buddies car. All are bigblocks. Mine is a 440 my sons is a 400 and my buddies is a 383. And as was said you HAVE TO SET THE TOP RING GAP RIGHT !!!

Ron

Posted By: Anonymous

Re: 383man - 05/13/10 03:05 AM

I agree with Maund--I have used tons of them with no problems-BUT..we see lots of them that have been destroyed---If you are on a budget and can read the instructions they work fine--we always give them some extra piston to wall--they may be engineers but I have to stand behind this stuff so to heck with 2 1/2 thou --give them some more --let them live---they can't take it with a sorry tune up --good racers can do about anything with them--back yard guys that have never understood a distributor etc need forged units to cover their behinds until they get an engine tuned and running proper and another note--not ALL hypers use extra ring gap..just the KB's Sealed Power made an awesome cast 440 piston but then it started being made in India and the quality went to crap--so...KB is the only cast pistons around with the compression height we need --so it is $330 for them or $600 for forged--they really took off and gained market share because of amazing coverage for all combos--NOT because they are good or for that matter cheap and BTW the new Mexico pistons have great pinfit unlike the USA made in the past

Posted By: Snoopy

Re: 383man - 05/13/10 05:03 AM

When did they start making them in Mexico and is it marked on the box?

Posted By: 67MIke

Re: 383man - 05/13/10 11:36 AM

while we are talking about KB pistons, what's a good choice for 400 (non stroked)
I have heard about about people having problems with hypers, but it was always when they did not set the ring gap correctly

Posted By: shaker340

Re: 383man - 05/13/10 04:58 PM

I just installed KB107 in my 360 and ordered moly rings for standard bore. I did not read the instructions.....and the engine is all together and in the car ready for first fire. What will happen if the ring gap is not set??

Posted By: MoparforLife

Re: 383man - 05/13/10 05:03 PM

Heat will/can cause the rings to butt together and in turn pull the top off the piston at the ring land. IMO take it apart now and re do it or do it later ant large cost.

Posted By: shaker340

Re: 383man - 05/13/10 05:27 PM

I was just at the Kieth Black website, sure enough they advise setting the ring gap. When we buy rings, what gap are they if one ordered for standard bore?? It seems like I will need around a 0.026 inch gap for street use.

Posted By: MoparforLife

Re: 383man - 05/13/10 06:14 PM

Old rule of thumb is .004 per inch of bore. 4 inch bore is .016 but not for these pistons. You are better off with too much than too little. Did you go to their chart?? Also did you read this article on their sight: http://www.kb-silvolite.com/article.php?action=read&A_id=56

Posted By: shaker340

Re: 383man - 05/13/10 06:33 PM

Yes I was looking at their installation instructions. It shows the top ring should be .0065 inch per inch of bore. They also mention the second ring too at .004 inch per inch of bore. I guess I'll be pulling the motor back out and tear into it to see what the ring gap is..

Posted By: Challenger340

Re: 383man - 05/13/10 06:40 PM

KB "Hypereutectic" Pistons are a "High Silicon" Alloy Cast Piston.
The Higher Silicon makes them stronger, by Hardening the Alloy,
albeit,
more "brittle" because of the Harder Material.

I've used a TON of them in Builds with no problems whatsoever,
that said,
The problems I have seen elsewhere, usually relate back to a Failure to follow the manufacturers(KB) Instructions, regarding Ring Endgaps and Clearance,
and secondary,
"severe tuning" mis-use, ie; really bad Detonation which tends the "Crack" the Harder/more Brittle Material Alloy.

FOLLOW KB's Instructions, and USE a timing light in Conjunction with enough Octane Fuel for the Compression Ratio,
and,IMO,
YOU WILL never HAVE A PROBLEM .

Posted By: MLR426

Re: KB pistons BREAK IN HALF??? - 05/13/10 06:47 PM

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I don't use them very often, but they are a good piston. The problem is, people don't read the ring gapping instructions. Since the top ring land is high, you MUST wide gap the top ring, or you will break that sucker!

That's right the ring gap is wide .028 top rings for 440.

logan426

Posted By: MoparforLife

Re: 383man - 05/13/10 07:03 PM

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Yes I was looking at their installation instructions. It shows the top ring should be .0065 inch per inch of bore. They also mention the second ring too at .004 inch per inch of bore. I guess I'll be pulling the motor back out and tear into it to see what the ring gap is..

I can't believe you put an engine together without checking the ring gap. Any engine build this is done.

Posted By: shaker340

Re: 383man - 05/13/10 07:14 PM

This is my first time replacing pistons and rings. The motor is in excellent condition measurement wise, bores were nearly perfect, very little taper and out of round, but it had 8:1 pistons in it....so I thought it would be good time to upgrade that while the engine needed new gaskets since it was starting to leak oil at the front and rear main seals.

Thanks to Moparts we all get to learn little things that make a huge difference. I'll fix it right.

Edit: I also read KB recommends a few degrees less timing. So 12 degree initial with 32 total would be fine using 91 octane fuel?

Posted By: gdonovan

Re: 383man - 05/13/10 07:58 PM

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The problems I have seen elsewhere, usually relate back to a Failure to follow the manufacturers(KB) Instructions, regarding Ring Endgaps and Clearance,
and secondary,
"severe tuning" mis-use, ie; really bad Detonation which tends the "Crack" the Harder/more Brittle Material Alloy.

LRE (a well regarded Chrysler IMSA car builder) thought I was on crack when I told them there was a problem.... till...

A bone turbo stock car they built broke 4 pistons.

At that point they stopped selling the pistons.

Why waste money on questionable parts? The short block is the foundation of your build.

Posted By: RoyceFlo73

Re: 383man - 05/13/10 08:05 PM

I don't think there is anything questionable about KB pistons. They state on their site that improper ring gap will crack pistons. They even have some pictures up for those who are interested.

I think it's just like anything when building cars, KNOW YOURE APPLICATION. Using hyper-pistons in a turbo motor or a 600hp drag car is as reckless as trying to run a 7 1/4 differential behind a mild 360. Sure it could be done, but it won't last long, and anyone should know that.

However, for the average guy running average HP for street use would be fine with KB107s. I'm buying my set next week and have talked to a few local shops and read a bunch of posts on here. ALOT of people use them successfully. All of those people knew what they were building and followed directions.

Don't use them if you are gonna run boost and don't run em if you plan on revving to like 8000rpm and drag racing it every weekend.

Posted By: Charger_440

Re: 383man - 05/13/10 10:05 PM

any experience with the rings that KB sells? or other suggestions

Posted By: moper

Re: 383man - 05/13/10 10:53 PM

Like anything else, there's good enough for a given application, and better. What I find funny are builders that can't spec a part that is adequate for a job, and others who spec the right part but can't execute the work properly. KB hypereutectics are a victim of the 2nd one most of the time. I've installed sets of them in 360, 318, 383, and 440 engines. All used different end gaps depending on intended use, and none have problems after years. Forged will give you a margine of error while KBs will not when it comes to ring gaps.
If you dont know and used a boxed set of rings, you MUST take it apart and check the gap on the top ring. Because what you need is bigger it's just a matter of the filing and any gaskets you tear. You can do this in the car if pulling it is a problem.

Posted By: ohiodemon

Re: KB pistons BREAK IN HALF??? - 05/13/10 10:57 PM

i run the kb-107's in my 360.
still going strong after 9 yrs.
as others have said, top ring must be set at proper specs.

KB pistons BREAK IN HALF???