Keith Black piston clearance

[Steve.k]

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.

[mag2555]

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.

[Frankshaft]

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

[Steve.k]

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.

[one finger john]

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

[mag2555]

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

[DaveMcLain]

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.

[Steve.k]

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.

[dfarr67]

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.

[Steve.k]

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

[cgarb]

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.

[Baprace]

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.

[Steve.k]

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

[MadBill]

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/

[SupStk]

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