KB Pistons Junk! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Reumster · 08-05-2002, 11:40 AM

Remember when I said my motor was acting up, did compression test and found broke plugs. Well my Keith Black pistons upper ring was breaking off! Yeap thats the second time it happened!

What pistons do you recommend? Cheap.

Regular rings or Chromoly?

71BBK10 · 08-05-2002, 12:15 PM

i've always been told, use cast if you just use like a glaze breaker, but if you dingle berry hone it then it should be good for molys, sorry don't really have any suggestions for pistons, how big a shot of nitrous do you have?

Beast388 · 08-05-2002, 12:29 PM

I've been using Keith Black hypereutectics for almost 3 years now with no problems.

Frankly, if you are using nitrous you should use nothing but forged pistons and chrome moly rings. There is just too much cylinder pressure there to use anything else.

Blazer1970 · 08-05-2002, 12:57 PM

Spark knock (detonation, pinging) will also break rings and upper ring lands like that.

Also, there is no such thing as a Chrome moly ring. There are rings with a chrome plating, and there a rings with a moly coating. Neither really has any effect on the strength of the ring, just the wear properties.

mikep · 08-05-2002, 01:06 PM

Thats right. Hypereutectics are nothing but fancy castings. They wont hold up with nitrous or supercharging . I dont know of any of the piston manufacturers who reccomend hypereutectics with nitrous. Forged is the way to go on the juice.

Chrome faced rings will hold up best under nitrous but they take an awful long time to break in. Moly faced rings seem to hold up just fine in my experience and they break in within a few hours.

wlee · 08-05-2002, 02:08 PM

The last set of chrome rings I used (and it will be the LAST set) still hadn't seated after 11,000 miles - use at your own discretion !!

brad69C-10 · 08-05-2002, 05:01 PM

Go to www.dirttrackthunder.com they sell Wiseco forged pistons with moly rings for $399, sometimes less. It is hard to beat that deal......they also have FREE shipping, so the final price is the final price.......just my 2 cents

Reumster · 08-06-2002, 12:10 PM

Well I never ran NOS with these pistons. So the nitrous didn't ruin them. So it must have been detonation. So first how do you tell if you have detonation, and second how do you fix it? I never heard know pinging, I allways ran 93 octane. Would running lean cause the upper rings to break? I just want this thing to run reliable! Damn I wish I'd bought a crate motor!

**BIG ORANGE** · 08-06-2002, 04:28 PM

I got KB pistons in my BB and they are doing fine.Your gap in your rings mite be the problem.Did you gap them yourself or where they prefit? Anyway good luck.

mikep · 08-06-2002, 04:29 PM

hypereutectics dont like hi revs either. Have you been twisting it too high?

Have you been running lean? Your'e using 93 octane? Whats your CR ?

Stroker · 08-06-2002, 05:11 PM

I think BIG ORANGE is on the right track. The KB pistons have a high top ring location and require a larger than normal ring end gap. If the gap is to small the ring ends will but and the rings or piston ring lands may break. Make sure your clearances are per KB specs.
http://www.kb-silvolite.com/speclear.htm#CHART
Be sure to carefully check the ring lands for damage, Good luck and let us know how everything works out.

Reumster · 08-07-2002, 12:50 AM

Yes I use 93 octane, running Trick Flow 68cc heads bored 40 over with flat tops. The motor was professionally built, and balanced, I shift at 6000 rpm and have had it to 7000 once or twice.

Should I try KBs again or go with another kind?

I think I may go to dish to reduce compression.

ChopTop · 08-07-2002, 01:49 AM

The most common reason a KB piston will break at the upper ring land is due to the ring coming together due to lack of clearance or excessive heat. KB's run different clearances than more traditional cast or forged pistons. One thing is for sure, everything needs to be right on the money for KB's to live, but considering a comparable forged, they are a bargain.

**MikeB** · 08-07-2002, 10:32 PM

SpeedPro Hypereutectic pistons for standard 5/64" rings, not the thin 1/16" rings. Sealed Power moly rings at .012 - .014 gap.

08-05-2002, 11:40 AM	#1
Reumster L.E.D. Freak Join Date: Jan 2002 Location: Polson MT Posts: 1,358	KB Pistons Junk! Remember when I said my motor was acting up, did compression test and found broke plugs. Well my Keith Black pistons upper ring was breaking off! Yeap thats the second time it happened! What pistons do you recommend? Cheap. Regular rings or Chromoly? __________________ Specializing in Custom L.E.D. inserts. http://www.ccled.com/ Contact me @ blazer2wd1972@hotmail.com (406)675-8082 or Joel @ jmcwaters@eps-corp.net 1972 2wd Blazer, 350/700R4/3:73 posi, err & Custom L.E.D. inserts! LOL

08-05-2002, 12:15 PM	#2
71BBK10 Teufelhunden Join Date: Oct 2001 Location: Camp Pendelton Ca Posts: 572	i've always been told, use cast if you just use like a glaze breaker, but if you dingle berry hone it then it should be good for molys, sorry don't really have any suggestions for pistons, how big a shot of nitrous do you have? __________________ 1971 K10 lwb fleetside 402 T350 205

08-05-2002, 12:29 PM	#3
Beast388 Suburbans RULE! Join Date: Jan 2000 Location: Clinton, IA 52732 Posts: 689	I've been using Keith Black hypereutectics for almost 3 years now with no problems. Frankly, if you are using nitrous you should use nothing but forged pistons and chrome moly rings. There is just too much cylinder pressure there to use anything else. __________________ --Ben 71 GMC Suburban 4X4 The "Beast" 388 CID Stroker, TH350, NP205, 8-lug D44, 14BFF w/ Detroit, 4.10:1 gears, 4-Wheel Disks 4" Lift, 35" MT/R's.

08-05-2002, 12:57 PM	#4
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	Spark knock (detonation, pinging) will also break rings and upper ring lands like that. Also, there is no such thing as a Chrome moly ring. There are rings with a chrome plating, and there a rings with a moly coating. Neither really has any effect on the strength of the ring, just the wear properties. __________________ Tim Last edited by Blazer1970; 08-05-2002 at 01:02 PM.

08-05-2002, 01:06 PM	#5
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Thats right. Hypereutectics are nothing but fancy castings. They wont hold up with nitrous or supercharging . I dont know of any of the piston manufacturers who reccomend hypereutectics with nitrous. Forged is the way to go on the juice. Chrome faced rings will hold up best under nitrous but they take an awful long time to break in. Moly faced rings seem to hold up just fine in my experience and they break in within a few hours. __________________ No truck :-(

08-05-2002, 02:08 PM	#6
wlee Just an Old Mr Goodwrench Join Date: Feb 2002 Location: Green Ridge, MO USA Posts: 259	The last set of chrome rings I used (and it will be the LAST set) still hadn't seated after 11,000 miles - use at your own discretion !! __________________ 1969 CST 20 Longhorn 1970 CST 20 Fleetside 1991 Jaguar Sovereign 1992 Mazda Miata

08-05-2002, 05:01 PM	#7
brad69C-10 Registered User Join Date: Jul 2002 Location: Ky. Posts: 35	Go to www.dirttrackthunder.com they sell Wiseco forged pistons with moly rings for $399, sometimes less. It is hard to beat that deal......they also have FREE shipping, so the final price is the final price.......just my 2 cents __________________ 69 C-10 Pro Street...........red on black...........big block and a lot of go fast stuff under the hood Still in progress ...........

08-06-2002, 12:10 PM	#8
Reumster L.E.D. Freak Join Date: Jan 2002 Location: Polson MT Posts: 1,358	Um Well I never ran NOS with these pistons. So the nitrous didn't ruin them. So it must have been detonation. So first how do you tell if you have detonation, and second how do you fix it? I never heard know pinging, I allways ran 93 octane. Would running lean cause the upper rings to break? I just want this thing to run reliable! Damn I wish I'd bought a crate motor! __________________ Specializing in Custom L.E.D. inserts. http://www.ccled.com/ Contact me @ blazer2wd1972@hotmail.com (406)675-8082 or Joel @ jmcwaters@eps-corp.net 1972 2wd Blazer, 350/700R4/3:73 posi, err & Custom L.E.D. inserts! LOL

08-06-2002, 04:28 PM	#9
BIG ORANGE Senior Member Join Date: Oct 2001 Location: Lancaster S.C. Posts: 4,752	pistons I got KB pistons in my BB and they are doing fine.Your gap in your rings mite be the problem.Did you gap them yourself or where they prefit? Anyway good luck. __________________ Things happen for a reason!

08-06-2002, 04:29 PM	#10
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	hypereutectics dont like hi revs either. Have you been twisting it too high? Have you been running lean? Your'e using 93 octane? Whats your CR ? __________________ No truck :-(

08-06-2002, 05:11 PM	#11
Stroker Registered User Join Date: Mar 2001 Location: Moore, Ok Posts: 1,149	I think BIG ORANGE is on the right track. The KB pistons have a high top ring location and require a larger than normal ring end gap. If the gap is to small the ring ends will but and the rings or piston ring lands may break. Make sure your clearances are per KB specs. http://www.kb-silvolite.com/speclear.htm#CHART Be sure to carefully check the ring lands for damage, Good luck and let us know how everything works out. __________________ 72 SWB parts and pieces Oklahoma

08-07-2002, 12:50 AM	#12
Reumster L.E.D. Freak Join Date: Jan 2002 Location: Polson MT Posts: 1,358	Well Yes I use 93 octane, running Trick Flow 68cc heads bored 40 over with flat tops. The motor was professionally built, and balanced, I shift at 6000 rpm and have had it to 7000 once or twice. Should I try KBs again or go with another kind? I think I may go to dish to reduce compression. __________________ Specializing in Custom L.E.D. inserts. http://www.ccled.com/ Contact me @ blazer2wd1972@hotmail.com (406)675-8082 or Joel @ jmcwaters@eps-corp.net 1972 2wd Blazer, 350/700R4/3:73 posi, err & Custom L.E.D. inserts! LOL

08-07-2002, 01:49 AM	#13
ChopTop Registered User Join Date: Jun 2001 Location: KINGWOOD TEXAS Posts: 515	The most common reason a KB piston will break at the upper ring land is due to the ring coming together due to lack of clearance or excessive heat. KB's run different clearances than more traditional cast or forged pistons. One thing is for sure, everything needs to be right on the money for KB's to live, but considering a comparable forged, they are a bargain.

08-07-2002, 10:32 PM	#14
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,470	SpeedPro Hypereutectic pistons for standard 5/64" rings, not the thin 1/16" rings. Sealed Power moly rings at .012 - .014 gap. __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!



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