Keith Black piston clearance

General engine tech -- Drag Racing to Circle Track

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In-Tech
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Re: Keith Black

Post by In-Tech » Thu Aug 03, 2017 12:50 am

lol, that and the coating is roughly the same cost as new KB's #-o . I really want to try the L2L Bill linked us to, looks really cool.

Off topic for pistons, I'm really interested what they have to say for a screw supercharger for my flow bench.
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Re: Keith Black

Post by Steve.k » Fri Aug 04, 2017 9:52 am

It is interesting to note that for supercharged or nitrous applications they do call for .005

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Re: Keith Black

Post by Racerrick » Fri Aug 04, 2017 11:15 am

don't do it... it will piston slap knock like crazy. Get a forged piston. IMHO KB hypers are better off left on the shelf. I refuse to use for anything other than ashtrays

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Re: Keith Black

Post by tenxal » Fri Aug 04, 2017 12:50 pm

SupStk wrote:Personally I'd be reluctant. Hypers are tough but brittle.
Agreed. Line2Line coating would be the way to go.

Hyper pistons being what they are, I'd not knurl (shudder)..... :shock:

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Re: Keith Black

Post by nickpohlaandp » Fri Aug 04, 2017 1:08 pm

Steve.k wrote:It is interesting to note that for supercharged or nitrous applications they do call for .005
Yeeesh, I wouldn't use hypers with nitrous. They tend to shatter if things go anywhere near wrong. They're not forgiving.

I used to run only KB hypers in my turbocharged 400's and when I would hone for clearance I would use 0.0008" x bore (in inches) and never had a problem. For the rings I used Total seal and I'd set the top ring at bore x 0.0080" and 2nd ring = bore x 0.0070". These engines ran under boost at constant rpm for hours on end and never had a problem.
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Re: Keith Black

Post by nickpohlaandp » Fri Aug 04, 2017 1:10 pm

nickpohlaandp wrote:
Steve.k wrote:It is interesting to note that for supercharged or nitrous applications they do call for .005
Yeeesh, I wouldn't use hypers with nitrous. They tend to shatter if things go anywhere near wrong. They're not forgiving.

I used to run only KB hypers in my turbocharged 400's and when I would hone for clearance I would use 0.0008" x bore (in inches) and never had a problem. For the rings I used Total seal and I'd set the top ring at bore x 0.0080" (+/- 10%) and for the 2nd ring = bore x 0.0070" (+/- 10%). These engines ran under boost at constant rpm for hours on end and never had a problem.
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Re: Keith Black

Post by cgarb » Fri Aug 04, 2017 1:42 pm

I will agree that if nitrous is in the mix on this, KB's are a no no...that's why I don't have those pistons anymore...lol. The nitrous oxide lowered the compression on one cylinder all by itself...lowered the compression and raised the crankcase pressure. Blew a nice chunk out right on top of the rod where the two valve reliefs come together.

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Re: Keith Black

Post by nickpohlaandp » Fri Aug 04, 2017 2:02 pm

When you introduce nitrous to a hypereutectic piston, well, I think Hot Rod magazine said it best years ago when they described them as "hyper-explosive"
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Re: Keith Black

Post by cgarb » Fri Aug 04, 2017 2:26 pm

I have seen then used with good results in Cleveland's that we're bracket motors. I used to race with a fellow who ran a Cleveland forever with a set of KB's in it. Probably close to 10 years, he went though the motor often, probably every 2 years he would look it over. Same cheap pistons the whole time though. Just new rings and bearings. Just use extra top ring gap and they will be fine.

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Re: Keith Black

Post by Steve.k » Fri Aug 04, 2017 3:07 pm

I will say i have used these pistons numerous times all woth good success. Only never looser than .0035. Other than a ultra high hp build i would not be afraid of them.

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Re: Keith Black

Post by Steve.k » Tue Aug 08, 2017 2:10 pm

[-X Well boys i phoned Keith Block and they said the same as most of you. To LOOSE!! .004 would be max. So I ordered a set of racetec forged that be happy at .005.

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Re: Keith Black

Post by nickpohlaandp » Tue Aug 08, 2017 3:53 pm

Steve.k wrote:[-X Well boys i phoned Keith Block and they said the same as most of you. To LOOSE!! .004 would be max. So I ordered a set of racetec forged that be happy at .005.
0.0008 x 4.125 = 0.0033 PTW. Perfect!

Edit: Oh, wait, your cylinders are already at the oversize... nevermind
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Re: Keith Black

Post by Steve.k » Tue Aug 08, 2017 6:02 pm

The tec suggested using a coating on pistons. They would coat the pistons the full 5 thou then let it wear off till the usual 2.-3 though clearance. He did say thise pistons were used in his car as a test or r&d with a 500 shot ofjuice. Didn't say what application though.no issues were encountered!

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Re: Keith Black

Post by nickpohlaandp » Tue Aug 08, 2017 6:23 pm

Steve.k wrote:... He did say thise pistons were used in his car as a test or r&d with a 500 shot ofjuice. Didn't say what application though.no issues were encountered!
I'd like to see that. That's a big hit for hypereutectic. If that's true it had to be pig rich and really conservative with the timing. I've run nitrous in a lot of my vehicles, and the only one that I had problems with was a 375 SBC with hypereutectic pistons. 200 shot nearly killed that motor. Replaced the broken pistons with a set of forged and ran the same setup (200 shot) and never had a problem with it.
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Re: Keith Black

Post by Steve.k » Tue Aug 08, 2017 6:30 pm

Were they KB or speed pro hypers?Its like anything the tune has to be right! He has no reason to feed me full of bs, they also sell icon forged which would get the job done as well.

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