Keith Black piston clearance

General engine tech -- Drag Racing to Circle Track

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Steve.k
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Keith Black piston clearance

Postby Steve.k » Sun Jul 30, 2017 10:58 pm

Anyone fit Keith Black hypers over .0045. On piston to wall or that to loose.Mud truck motor.Owner has pistons already and block is bored. Hoping to hone and run but be on looser end of spec.
Last edited by speedtalk on Sun Aug 13, 2017 9:19 am, edited 1 time in total.
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mag2555
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Re: Keith Black

Postby mag2555 » Mon Jul 31, 2017 5:34 am

You would be right at end of the tolerence with .0045"!
.0045" will likely not work well with 180 degree or less of water temp.
If you go the Hyper route don't forget that they call for different ring gap specs also.

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Re: Keith Black

Postby Frankshaft » Mon Jul 31, 2017 7:36 am

Its a mud truck engine. Its going to be junk by the end of the summer anyhow. I would run it.

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Re: Keith Black

Postby Steve.k » Mon Jul 31, 2017 7:44 am

He was running a engine that was built. Thought it was a 400 2v setup but ended up a 351m. Won quite a few trophies. Surprised both of us. Now going cleveland 4v heads with the kb177 flattops on 400. He had good pistons from another project he wanted to use. The block however is .030 already and need a little touch to cleanup. Thus the over .0045.

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Re: Keith Black

Postby one finger john » Mon Jul 31, 2017 8:29 am

Look into having the pistons coated to bring up the clearances.

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Re: Keith Black

Postby mag2555 » Mon Jul 31, 2017 8:40 am

Your going to need to keep the revs above 5K with those heads even with 400 cid under them!

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Re: Keith Black

Postby DaveMcLain » Mon Jul 31, 2017 8:43 am

Steve.k wrote:He was running a engine that was built. Thought it was a 400 2v setup but ended up a 351m. Won quite a few trophies. Surprised both of us. Now going cleveland 4v heads with the kb177 flattops on 400. He had good pistons from another project he wanted to use. The block however is .030 already and need a little touch to cleanup. Thus the over .0045.


Just knurl the skirts a bit to tighten them up a bit. A friend of mine ran this same combo but using an old TRW domed 351C piston. 4V closed chamber heads on a 400 using the stock 4V Cleveland iron intake and a set of spacers all because of the rules for the class that forbid a big block engine in a Bronco or Blazer. His engine also had to make 15 inches of manifold vacuum at 800rpm so having a very high compression ratio helped a lot. He won a lot of races and later sold the engine. It certainly was not junk by the end of the season. I think they turned it about 6000rpm or a little more most of the time.

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Re: Keith Black

Postby Steve.k » Mon Jul 31, 2017 8:47 am

Yes i have used this combo before. With 4v cc heads mild solid flat tappet and these pistons motor made 551@6300.Dave he has the port o sonic intake for 400 but we were thinking maybe going to either torker or strip dommy.

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Re: Keith Black

Postby dfarr67 » Mon Jul 31, 2017 9:30 am

My 383 is disappointing loose with these pistons- but when fully hot quietens right down, probably the 0 offset pins don't help. I've read it doesn't hurt the pistons and I can hope it cuts friction a bit. Not what I wanted it's what I ended up with.

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Re: Keith Black

Postby Steve.k » Mon Jul 31, 2017 12:52 pm

Sounds like should be ok. We give it a whirl !!

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Re: Keith Black

Postby cgarb » Mon Jul 31, 2017 5:11 pm

I say run it. I ran a set of KB's with one bore loose from a ring mishap during assembly. Honed the mark out and it took close to .002 larger to get it cleaned up. That piston looked the same as all the other skirts when I tore it down. Just make sure it's warmed up before he hits the pit.

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Re: Keith Black

Postby Baprace » Mon Jul 31, 2017 6:12 pm

cgarb wrote:I say run it. I ran a set of KB's with one bore loose from a ring mishap during assembly. Honed the mark out and it took close to .002 larger to get it cleaned up. That piston looked the same as all the other skirts when I tore it down. Just make sure it's warmed up before he hits the pit.


Good advice, I agree 100% just make sure the ring end gap is loose enough.

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Re: Keith Black

Postby Steve.k » Tue Aug 01, 2017 7:55 am

Thinking we did a cleveland loose awhile back with same pistons. Not sure it was this loose though.

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Re: Keith Black

Postby MadBill » Wed Aug 02, 2017 9:46 pm

I say coat them. I had my BBC pistons built up 0.014" on the diameter, from 0.010" to a self-clearancing zero by Line2Line: https://www.line2linecoatings.com/
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Re: Keith Black

Postby SupStk » Wed Aug 02, 2017 11:34 pm

Personally I'd be reluctant. Hypers are tough but brittle.
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