Has anyone here had a bad experience with them?? I ran a set years ago in a 355 that I raced. They were 11:1 pop-ups with the 1/16 ring pack. I ran them for 4 years with no issues, then sold the motor to a guy who ran them for another few years...no issues. Lately I've been reading online, and hearing from other racers that KB pistons are JUNK!! What happened? Did they change the design, machining?? Anybody have any issues?

Far from my favorite but I've never had any problems when people want to use them , if they are hyperuetics you have to follow their ring gap specs or you'll have problems

I think most of the complaints are about their Hyper pistons. Ring gap has to be set a little wide and exactly per manufacturer specs or may have problems. I am using KB forged in a BB I am building and don't expect any issues.

They (the hypereutectic ones) don't hold up well to the kind of vicious detonation that can happen in a nitroused or boosted application, but I've run quite a few sets of them in many motors successfully. I've never broken them except while working my way up a fairly steep learning curve with my last few supercharged engines.

There's nothing wrong with KBs, it's just that hypereutectic pistons aren't what you want from any manufacturer in a power-adder application.

KB has an excellent article on their website about hypers vs. forged that your should read so you understand WHY.

The short version is: it has almost nothing to do with the strength of the piston. Hypers can be every bit as strong as forged. The difference has more to do with how they manage the heat of combustion. Forged units pull heat out of the chamber/piston face much faster than hypers. Hypers keep it "bottled up" above the piston. In heavy detonation when combustion temps spike wildly the heat doesn't get carried down the piston body away from the top ring as quickly. Causes the top ring to overheat, expand, and close the gap down to nothing. When the top ring gap hits zero the ring locks in the bore and on the next down-stoke it rips chunks of the ringland off above the top ring. Those chunks then do very bad things to the motor very quickly (ka-boom!).

When you've successfully blown one up, it looks like this if you got away easy:

http://i226.photobucket.com/albums/dd81/dnickle614/IMG_0611.jpg

And it looks like this when you really grenade one:

http://i226.photobucket.com/albums/dd81/dnickle614/IMG_0612.jpg

No problems here KB 13.5:1 forged

My Scat otating assembly (385 stroker) came with Keith Black FHR series 19.6cc dished forged pistons. I have a book by David Vizard and he says he uses Keith Black Pistons in 1 out of every 3 engine builds he does. He says even their claimer series pistons are of good quality.

I'm glad I bought his book. He has a lot of good information it besides just pistons. Honestly, if I didn't go with the Scat kit that came with the KB FHR series forged pistons I wouldn't have been able to afford forged pistons at all.

That being said, I'm not building a race motor. Just trying to get an honest 350 HP and 425/450 FT. LBS. of torque. I might add a 75 to 100 horse hitter down the road. From everything I've read and have been told, they should work really well with my set up.

I know they need a special top ring gap from when I put mine together. I have a buddy that lifted all 8 top ring lands off his popups in a 383. Made a SERIOUS mess at 6000 rpm's at 1000 feet. Now I'm helping a friend put a 400 horse 350 together for a street car on a budget. You cant beat a set of these pistons at $190.00 in my opinion. I'm starting to think that all the negative I've heard about them is from not paying attention to the top ring gap.

Detonation will damage any piston. forged or cast if allowed to continue. Its like hitting the piston with a hammer.

I ran the KB Hypers on many motors including a 500+hp 406 without issue. I think all the issues you hear about are from ppl that didnt know what the hell they were doing with there engine.

I ran the KB Hypers on many motors including a 500+hp 406 without issue. I think all the issues you hear about are from ppl that didnt know what the hell they were doing with there engine.

this right here^^ pretty much stems from the ring gap issue along with not pulling the recommended timing in combonation with trying to get away with not enough octane or too lean and onsetting detonation.
andy

No problems out of Keith Black 2618 Premium Forged Pistons, They are on Wiseco Forgings (the SB ones I use)

One of the best off the shel pistons in my opinion is Probe Industries Sportsman Race Series

http://www.probeindustries.com/

I ran the KB Hypers on many motors including a 500+hp 406 without issue. I think all the issues you hear about are from ppl that didnt know what the hell they were doing with there engine.

Here is a video of our 100% stock block, stock crank, stock rods polished by me and oil holes drilled in them :) , OE KB .030" over pistons, GM 291 327 heads bowl ported only, flat tappet camshaft

Best pass 10.41 and this was a 10.43 pass in the video. 2850 race weight. So I agree with CamaroMan79 :)
http://i510.photobucket.com/albums/s347/331Trmnatr/th_MVI_0584.jpg (http://s510.photobucket.com/albums/s347/331Trmnatr/?action=view&current=MVI_0584.flv)

We are now making more power, same engine but some block tricks we have done in the past that was not done on above engine, Scat Rods, Forged Flat Tops, ported the exhaust runners on the 291 Heads, and thus far it has wheel hopped to a 1.42 60 foot time with a 10.19 @132.28mph, look for some 10.0/9.90's in weeks to come :cool:

Here are some photos of some of the best off the shelf pistons in my opinion and the best value for your money

Probe Industries Sportsman Race Series 2618 Domed 355 High Compression Piston (Notice how round the dome is, almost not edges)
Compression Height 1.260"
Bore Size 4.030"
Deck Thickness .175"
Top Design .500" Tall Hollow Dome
Piston Weight 422grams (VERY LIGHT)
Wrist Pin weight 118grams
http://i510.photobucket.com/albums/s347/331Trmnatr/IMGP0036.jpg

Probe Industries 4032 Flat Top 355 Pistons
http://i510.photobucket.com/albums/s347/331Trmnatr/IMGP0033.jpg

Probe Industries Sportsman Race Series 2618 Domed 406 High Compression Pistons showing the underside, Notice how thick this series is from the skirt to pin boss & around the pin boss, Notice the skirt thickness too
http://i510.photobucket.com/albums/s347/331Trmnatr/ProbeSRSPiston.jpg

Probe Industries Sportsman Race Series 2618 Domed 406 High Compression Pistons from the top
Compression Height 1.125"
Bore Size 4.155"
Top Design .175" SOLID dome
Deck Thickness .200"
Piston Weight 490grams
Wrist Pin Weight 118grams
http://i510.photobucket.com/albums/s347/331Trmnatr/Probe406piston.jpg

Probe Industries Premium Race Series Pistons (stopped making them for some changes, may start again and may not, I hope they do, I'm posting this as there are many floating around and I believe Probe still has a few of these)
Even though they are feather light, Notice the skirt thickness, material from the skirt to pin boss and material around the pin boss
Compression Height 1.125"
Bore Size 4.030"
Deck Thickness ? (no data any more, I think these are .150" decks IIRC)
Top design Flat Top
Piston Weight 329grams
Wrist Pin Weight 88grams (65grams with tool steel pin)
http://i510.photobucket.com/albums/s347/331Trmnatr/ProbePRSpiston.jpg

Now here are some photos of some Keith Black Premium Forged 2618 Pistons, Now called ICON Series. All pics below are of the following piston,
Compression Height 1.385"
Bore Size 4.030"
Deck Thickness ? (they hold up very well)
Top Design .400" Tall Dome
Piston Weight 480grams (which is light for bore, dome and CH piston)
Wrist Pin weight 132grams (optional 107gram Tool Steel available)

Top View
http://i510.photobucket.com/albums/s347/331Trmnatr/IMG_0400.jpg

Underside View
http://i510.photobucket.com/albums/s347/331Trmnatr/IMG_0542.jpg

** The Probe Industries Pistons can be sent to Rebco Machine and have the pistons made even lighter, If your application calls for it, Probe are some of the lightest off the shelf pistons out there but if your application needs them lighter it can be done at Rebco Machine. Those Hollow Dome Pistons for the 355 can be 400grams, If the application calls for it

The Keith Black 2618 Premium Forged Pistons can be lightened some, not as much as the Probe Industries Sportsman Race Series

Just to compare to off the shelf pistons, you can make a better decision based on the information below

This is a set of Custom Ross Racing Pistons. I myself look at Probe Industries and Keith Black, then if I need a custom Ross Racing Pistons is the way to go "In My Opinion"

These are solid domes and very thick decks with lightening, Notice the dome shape/profile,,,

Piston specs and pics
Bore - 4.060"
Compression Height - 1.375"
Top ring - .031"
Second ring - 1/16" back cut
Oil Ring - 3/16" 5-10 pound (I prefer the 3/16" groove for larger drain back holes, just my opinion)
Effective dome cc's - 14cc's
Dome height - .400"
Intake valve pocket depth - .305"
Exhaust valve pocet depth - .260"
Pin - .927"
Pin wall - .150" Thick Wall
Pin weight - 119grams

Deck thickness front - .510"
Deck thickness rear - .515"
Minimum thickness under intake pocket - .206"
Minimum thickness under exhaust pocket - .289"
Minimum thickness of deck & dome combines - .910"
Intake valve pocket to top ring groove - .108"
Exhaust pocket to top of ring groove - .122"
Skirt - .139"
Side relief - .102"
Thickness at fire slot - .751"
Pin hole to side of pin boss - .086"
Pin engagement in pin boss - .625" per side

Weight
453grams
453grams
453grams
454grams
453grams
456geams
455grams
453grams

Here are the pics,,,

Top Side View
http://i510.photobucket.com/albums/s347/331Trmnatr/IMG_0573.jpg

Bottom Side View showing all the internal lightening
http://i510.photobucket.com/albums/s347/331Trmnatr/IMG_0575.jpg