KB hypereutectic pistons

[rebelyell]

The pistons are .060 KB135's...18cc dish with 1.425" compression height. I bought them some 20 years ago for one of my own 388's but ended up changing directions on that build, so I've been dragging them around forever. With a 5.85 rod they will work in a 350.

I've got several sets of heads that I can use with these...56cc 601 castings, several sets of vortecs, and a set of ported 50cc chamber 200cc RHS heads that flow iirc 288@.550 or .600. I've been anxious to use these RHS heads, but it may be better to use one of the lesser heads with these pistons, and save the RHS heads for my roller block.

KB135 --- requires obsolete thick truck rings ... I get it; save $ & use what ya got , but ...
Racetec (USA) has an Autotec line (USA) of forged 4032 pistons --- probably priced about what KB135 retails for today.
http://racetecpistons.com/wp-content/up ... atalog.pdf

[1700camaro]

Would you trust them on a iron head 350 with 10.5-1 compression and an occasional blast to 7k rpm's, on 91-93 octane pump gas? This will be just a fairly hot driver.

Follow what just about everyone else said in this thread & you will be fine.

I still have my back up motor with about 3,000 1/4 mile runs on it. The KB hypereutectic pistons were replaced at about 1,500 passes, just because & nothing wrong with them. The motor is a 385 SBC with cast iron heads, 13.8 compression & went through the traps at 7,000 - 7,200. The car ran mid 10s @ 3,300 lbs.

[panic]

recuperating parts doubles with every 1000 rpm

Reciprocating load (piston, rings, pin, locks, rod small end, etc.) ~ with the RPM^2.
6,000 > 7,000 is not doubled, but +36%, etc.

[rustbucket79]

Wonder why all the fuss over hypers, darn near ever GM car and truck has had them since the late 90's. Sure don't hear anything about them other than the piston slap complaints on the LS hyper ones. My 5.3 has hypers and 250K noisy for the 1st 30 sec. after that the engine runs perfect. I say run'em but with KB you need to run more ring gap on the top ring.

Because the KB’s have minimal material thickness above the top ring and the lid thickness is typically very thin. They need significantly more top ring gap.

So long as everything is right, they’ll live a long time.

[GARY C]

Wonder why all the fuss over hypers, darn near ever GM car and truck has had them since the late 90's. Sure don't hear anything about them other than the piston slap complaints on the LS hyper ones. My 5.3 has hypers and 250K noisy for the 1st 30 sec. after that the engine runs perfect. I say run'em but with KB you need to run more ring gap on the top ring.

I was thinking the same thing, my 2001 6.0 2500 HD lived at least 400,000 miles before we lost contact, it had lifter noise that sounded like a diesel from about 200,000 on, No issues with my 2009 so far at 170,000 miles... Not sure what my 1996 vortec had but it was at 260,000+ when I sold it.

[blackford]

Wonder why all the fuss over hypers, darn near ever GM car and truck has had them since the late 90's. Sure don't hear anything about them other than the piston slap complaints on the LS hyper ones. My 5.3 has hypers and 250K noisy for the 1st 30 sec. after that the engine runs perfect. I say run'em but with KB you need to run more ring gap on the top ring.

Because the KB’s have minimal material thickness above the top ring and the lid thickness is typically very thin. They need significantly more top ring gap.

So long as everything is right, they’ll live a long time.

...and hypereutectic aluminum tends to reflect heat more than other types of aluminum which results in the top ring operating hotter. I have had KB hypers in a 331 SBF for 18 years and I rev it to 7100. I rebuilt the engine once and the pistons looked great so I reused them.

[rebelyell]

seems all or virtually all serial production passenger vehicles in last 30 years or so, which have OE hypereutectic pistons, Also have a well engineered OE knock-sensor-ECM system to help prevent spark knock/detonation ... right? Nowadays, all the newer stuff has hypers but also have fast ECM.

[F-BIRD'88]

You'll also find that kb hypers with proper quench
Tend to want 1-2 deg LESS max WOT timing.
More heat efficient.

[skinny z]

Not necessarily KB specific but in last couple of iron headed SBCs I've built with Speed Pro hypereutectics, I went through tuning phases with plenty of heavy spark knock as well as light rattling when in lean cruise and super advanced.
I can report that the pistons held up well with no damage to them or the rings. From the gloom and doom predicted when I was looking for some Speed Talk assistance, I might have been lucky.
At most there was a speck or two on the plugs but overall they took a lot of punishment. Drag racing. Sustained WOT. Plenty of miles too.

[Lizardracing]

I have used them lots of times and have had no piston related issues.
I will add that they are brittle, and don't melt but shatter and when that happens the small end of the rod let go and breaks lots of other things too unlike a forged piston that will usually melt but still control the small end of the rod.
Pay attention to the top ring gap and skirt clearance and you'll be just fine.

[rustbucket79]

Not necessarily KB specific but in last couple of iron headed SBCs I've built with Speed Pro hypereutectics, I went through tuning phases with plenty of heavy spark knock as well as light rattling when in lean cruise and super advanced.
I can report that the pistons held up well with no damage to them or the rings. From the gloom and doom predicted when I was looking for some Speed Talk assistance, I might have been lucky.
At most there was a speck or two on the plugs but overall they took a lot of punishment. Drag racing. Sustained WOT. Plenty of miles too.

The Speed Pros are an entirely different animal than the KB’s. Much thicker lids, thicker above the top ring land, and much tighter piston to wall clearance make for a more forgiving and quieter engine. You typically can use stock ring gaps too.

We use Speed Pro’s all the time.

[Steve.k]

I’ve had extremely good luck with kbsilvolite hyper pistons. Loose ring gap is a must but they work awesome. Had one engine with close to 7 years on it. Tore down and pistons were perfect so reused. For the bang for buck pretty tough to beat. There light years ahead of the heavy old speed pro pistons we were using before. Not afraid to use in most engines for street or drag. These engines were all under 600hp. Highest one was 408 cube around 580hp.

[Mark O'Neal]

Tuneup, Tuneup, Tuneup.....

[Steve.k]

I remember when i first bought the kbs I talked to there tec for some info. He told me his own 347 stroker was the test mule. They had a 350 shot of nos on it and it worked awesome. As mark mentioned he also stressed tuneup tuneup tuneup. But thats like everything I suppose.

[1980RS]

Tuneup, Tuneup, Tuneup.....

That about sums it all up right there.