Go Go Gadget Arms

iTrader: (2)

I put these KB hyperutectic's in 100 miles ago. 2 are melted no dammage to the head or valves. what should i do. compression ratio is close to 12.5:1

Go Go Gadget Arms

iTrader: (2)

cylinders number 5 and 4

MrOverkill

iTrader: (1)

I hate to say bro but you need to step up to a forged piston, its obviously detonating which is causing the piston to rock back and forth in the bore. KB now makes a very nice and affordable forged slug, though I'd go TRW/Speed Pro if your on a budget. Go to summit or Jegs' site, you'll find what you need. HyperuCRAPtic pistons are only good to about 450hp and can NOT handle ANY detonation......

1_bad_TA

iTrader: (6)

are you spraying or all motor?

trackbird

iTrader: (4)

Those don't appear to be melted, they appear to be broken/fractured. What are your ring gaps set to? The KB pistons require a specific formula for setting ring gap. Those pistons reflect more heat into the rings and combustion chamber and that causes the top ring to expand more than usual. Once it expands far enough that the ends of the rings butt together, the ring tries to stick in the bore and breaks the top of the piston off. When that happens, they look just like what you have pictured. If you used standard ring gaps, that's your problem. The formula is on KB's website, I'd have to look it up because I don't remember it off the top of my head. I am running their pistons in one of my engines and I've had great luck with them.

bluebeast

iTrader: (1)

SRP forged is a great piston.......get them

MrOverkill

iTrader: (1)

+1 those slugs swell up quite a bit when warm, in fact they need extra piston to wall clearance and you need to file fit a set of rings if you want them to be correct. They are not worth the trouble, and are not really much better than any other cast piston from my experience. Again I IF it were MINE I would take those pistons and chuck them as far as I could

JTM

Improper ring gap did that.

Go Go Gadget Arms

iTrader: (2)

thats f'n lame. the dood at summit told me not to get the file fit ones.

who votes i get a new set of flat top forged so i can run pump gas. and who votes i get 2 new slugs and rings and save the money to spend on 100oct?

Go Go Gadget Arms

iTrader: (2)

and what is the gap spec if i file them. overbore is .040 if it makes a difference

thanks,
Greg

MrOverkill

iTrader: (1)

New pistons is my vote!

trackbird

iTrader: (4)

Greg,

The tech info is here:

http://www.kb-silvolite.com/download...Automotive.pdf

If it's a street, normally aspirated engine, the "end gap factor" is 0.0065" (Drag engines have a factor of 0.0075, so figure your use and correct accordingly). You multiply the bore size by that "factor" and you'll get the proper top ring gap. KB has a calculator on their website here:

http://www.kb-silvolite.com/calc.php?action=ring


If that's a 4.040 bore in a street application (I'm assuming it's a 350 block and not a 400), ring gap should be .026". Piston to wall clearance for bores under 4.100" is .0015-.0020".

If in doubt, look at the chart in that first link I posted. A little extra gap won't hurt you as bad as having it too tight (as you've already learned).

Hope that helps!

bluebeast

iTrader: (1)

from what i have heard and i may be wrong keith black products arent that great stuff, for a daily driver 300 crank hp rebuild maybe....... JE, SRP, MAHLE, CP , DIAMOND are better products i would say and not all are expensive

trackbird

iTrader: (4)

Yes, and no. The KB's have some benefits (if you use them properly). They reflect more heat into the combustion process, so the engine will be slightly more efficient (and make slightly more power). They are very strong pistons, but they are also somewhat brittle due to that strength (they are "hard" due to having high levels of silicone in them.). They don't like detonation, they just wont put up with it. They will handle high RPM (as long as the piston to wall clearance is correct and they don't rock in the bore). They require less total timing, that's back to the increased effeciency. So, they have some nice benefits when used carefully and according to their instructions. If you have to build an emissions legal car, the KB's will typically have less blow by than a similar forged piston due to the tighter piston to wall clearances. And, they are not terribly expensive.

They ARE NOT forged pistons. If you want to spray an engine, or are pushing the limits of compression and risking detonation, you should consider something else. You really can't go wrong with Diamond, J&E, SRP and others. Those are all excellent pistons.

We have run the KB's in an almost 8,000 rpm 302 Ford in a road race car. They were in the engine for about 4 seasons before a rod bolt let go and trashed the whole works. And I'm currently using them in a mild autocross/track car that's about 400 flywheel hp and spins to just under 7k on occasion (usual shift point is 6,400, but I'll "stretch" gears on occasion instead of shifting up and right back down). They've worked great in that engine as well.

As always, read everything you can, follow the manufacturers directions and make your purchase decision based on your intended use...just like everything else we buy for performance use.

And, your results may vary.

JUICED96Z

iTrader: (2)

Id never trust the Summit or Jegs people, to many people that have ended up returning stuff just because they said to "get this part" and come to find out its the wrong one or does not fit.

I have TRW forged pistons in my 468 and they have lived on a 300 shot more then a few times.

Go Go Gadget Arms

iTrader: (2)

thanks for all your help. before i order 2 new pistons what rings should i get?

this engine is in an off road desert racing truck. it runs in the 4000-6200 rpm range all day. it has cast iron heads with angled plugs, don't know what cc runners but they are significantly larger than a set of ported camel humps i had on an old motor, i think they are world but im unsure.202-160's 64cc and crew in studs. edelbrock rpm cam. crane roller rockers.

heres a few Q's about how i should tune it.

just got an MSD pro billiet vacuum advance w/ 6al box and high vibration coil.

what advance springs should i run?
base timing?
total timing?

im currently running autolite racing ar133 spark plugs. should i get some stock ac delco's to decrease chances of detonation?

trackbird

iTrader: (4)

I run Speed Pro plasma moly rings and they've done very well for me. My rings were file fit per the KB instructions I linked.

I'd watch your total timing, I think KB give some guidelines in that paper that they typically use 2-4 degrees less timing than a forged piston. That seems correct based on my experience. Don't go wild on total advance.

As for the spring kits, I can't say much there. I'm using an MSD pro billet, but mine is controlled by a TPI computer.

MrOverkill

iTrader: (1)

JE nitrous slugs w/ Hellfire rings for my street engine.


I have also had great success w/ SRP which is JE, Wiseco, Diamond, Mahle, and Probe. I think for most people budget and whats on the shelf is the limiting factor, I have quite a few sets of pistons custom made which takes time. I almost always buy 2 extra pistons when I build an engine just in case.....

JUICED96Z

iTrader: (2)

I have heard good things about the Hellfires also......

When gaping I would first ask the piston manufacturer.

MSD may or may not be able to help you with the timing questions but from what I hear there customer service people are not the smartest people out there. Mor of you ask them a question and they look up the question or problem in there FAQ's and thats it.

At the very least I am sure they can give you a baseline.

Timing also depends on what gas you are runing.

Go Go Gadget Arms

iTrader: (2)

ya thats what i figured about msd. ill be trying to run premium california gas which is horrible with octane boost to try and achieve close to 93oct