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Max clearance with hyper pistons 5-.00 #2806036
08/07/20 07:59 AM
08/07/20 07:59 AM
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pennsylvania
poboyengineering Offline OP
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I have a set of KB107 pistons and their website says. 001-0045 p/w clearance. My block
will give me. 008. How loose can they be run?


It may be ugly, but it sure is slow.

Girls comb their hair in rear view mirrors and the boys try to look so hard....
Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806038
08/07/20 08:02 AM
08/07/20 08:02 AM
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80fbody Offline
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Have a short block with similar situation. Thought about having the pistons coated since they are new and came with the shortblock. Likely to crack/collapse the skirts on those style pistons with too much piston slap.

Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806090
08/07/20 10:43 AM
08/07/20 10:43 AM
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madscientist Offline
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Originally Posted by poboyengineering
I have a set of KB107 pistons and their website says. 001-0045 p/w clearance. My block
will give me. 008. How loose can they be run?


Line2line coating is what you want.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Max clearance with hyper pistons 5-.00 [Re: madscientist] #2806107
08/07/20 11:32 AM
08/07/20 11:32 AM
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Romeo MI
MR_P_BODY Offline
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Originally Posted by madscientist
Originally Posted by poboyengineering
I have a set of KB107 pistons and their website says. 001-0045 p/w clearance. My block
will give me. 008. How loose can they be run?


Line2line coating is what you want.


With that much clearance you are asking a lot for a coating.. I had 1 set of pistons coated and they
wouldnt guarantee any with that much.. most they would go was .004.. I ran that engine on the
loose side.. it had piston slap when cold but as it heated up it would get better
wave

Re: Max clearance with hyper pistons 5-.00 [Re: MR_P_BODY] #2806143
08/07/20 01:10 PM
08/07/20 01:10 PM
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lewtot184 Offline
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I think .008" is way too much. I've done coatings to pick up a little but only .001"-.002" and to be honest i'm not sure it was a big help. catalog states minimum clearance at .0015". hyper's don't grow like forged do. depending on the usage i'd probably do .0025"-.0030".

Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806176
08/07/20 02:35 PM
08/07/20 02:35 PM
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Originally Posted by poboyengineering
I have a set of KB107 pistons and their website says. 001-0045 p/w clearance. My block
will give me. 008. How loose can they be run?


Follow the piston manufacturers suggested clearance specs.

As for Lins2Line, call them, I think they will tell you they can help you. I had .004” added to my pistons and no problems.

Re: Max clearance with hyper pistons 5-.00 [Re: 80fbody] #2806185
08/07/20 02:56 PM
08/07/20 02:56 PM
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pennsylvania
poboyengineering Offline OP
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Originally Posted by 80fbody
Have a short block with similar situation. Thought about having the pistons coated since they are new and came with the shortblock. Likely to crack/collapse the skirts on those style pistons with too much piston slap.


This is what I'm afraid of since they are pretty brittle.This block was from a dirt track racer, and it has 8 sleeves and they measure 4.005, pistons at 3.993. The pistons are new, and the block just needs a quick hone.


It may be ugly, but it sure is slow.

Girls comb their hair in rear view mirrors and the boys try to look so hard....
Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806193
08/07/20 03:22 PM
08/07/20 03:22 PM
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Mr. Potatohead Offline
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That be a no go.

I run some hard at .003 on cold assembly and they rattle like old trw-s.

Id think at your specs if you run it hard your gonna be crackin skirts.

The low end forged are not much more then a new set of hypers these days. $100 diff.

The lower end icon forged is what im talking about.

Last edited by Mr. Potatohead; 08/07/20 03:24 PM.

My family is a bunch of Fruits and Vegetables and many cant tell us apart. EAT ME!
Re: Max clearance with hyper pistons 5-.00 [Re: Mr. Potatohead] #2806242
08/07/20 06:12 PM
08/07/20 06:12 PM
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merpar Offline
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Way too much clearance. I would find another block or buy new pistons. Those pistons have a short skirt to begin with and .008 clearance they would rock really bad. Even in a hot motor. Like potatohead said that is a no go.

Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806475
08/08/20 09:56 AM
08/08/20 09:56 AM
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Monrovia, So-Cal, USA
racerhog Offline
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She is going to be a knocker... smile


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Monrovia So-Cal
Re: Max clearance with hyper pistons 5-.00 [Re: racerhog] #2806490
08/08/20 10:30 AM
08/08/20 10:30 AM
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Romeo MI
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Years ago I would run nylon buttons to reduce piston slap in conditions like yours
but I havent heard of guys using buttons in a long time.. I would think some still use
them shruggy
wave

Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806567
08/08/20 02:03 PM
08/08/20 02:03 PM
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One of the advantages of the KB piston is that it has a stable expansion rate, it does not expand very much when it gets hot. This allows a smaller running clearance, less piston rocking in the bores, and better ring seal. But the silicone in the alloy does make them brittle, they do not like detonation, and I think they would not like to be slapping around in a bore as well. I know that if they are run loose you will sacrifice some ring seal. I know it is tempting to save a few bucks, but just do it right, if the block is good enough to use, buy pistons to fit, if the block is questionable get a different one and bore it to fit the pistons. You will be much happier in the long term.

Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806608
08/08/20 03:50 PM
08/08/20 03:50 PM
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Originally Posted by poboyengineering
I have a set of KB107 pistons and their website says. 001-0045 p/w clearance. My block
will give me. 008. How loose can they be run?

Are you feeling lucky?
Are you willing to loose a block over not knowing how much is to much clearances on those type pistons work tsk twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Max clearance with hyper pistons 5-.00 [Re: Cab_Burge] #2806693
08/08/20 08:52 PM
08/08/20 08:52 PM
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pennsylvania
poboyengineering Offline OP
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No, I'm not willing to sacrifice this block on an experiment, hence my question.
I appreciate the advice, but it seems to bring up a couple of more.
Since the block is 4.005, will I be able to get pistons that aren't under 4.000?
Or, since this has 8 sleeves, can they be bored? I don't mind going 4.030 if needed.


It may be ugly, but it sure is slow.

Girls comb their hair in rear view mirrors and the boys try to look so hard....
Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806707
08/08/20 09:43 PM
08/08/20 09:43 PM
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jwb123 Offline
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If the bores are straight and true, lots of companies make custom pistons for what ever size you want. A lot of the companies will take a stocking shelf piston and machine it to a slightly bigger bore for a minimal charge. I do it all the time with Ross pistons with deck height changes. Call them

Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806755
08/09/20 08:28 AM
08/09/20 08:28 AM
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Romeo MI
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You could call a few piston companies and ask what is the max bore allowed for their piston
before you change the bore calls are cheap and could be quick
wave

Re: Max clearance with hyper pistons 5-.00 [Re: MR_P_BODY] #2806766
08/09/20 09:16 AM
08/09/20 09:16 AM
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lewtot184 Offline
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you can buy another set of kb107's in .020" or .030" for less than $300 dollars. that's cheap! so why waste time and money with custom pistons if the KB's will work?

Re: Max clearance with hyper pistons 5-.00 [Re: lewtot184] #2806769
08/09/20 09:34 AM
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Originally Posted by lewtot184
you can buy another set of kb107's in .020" or .030" for less than $300 dollars. that's cheap! so why waste time and money with custom pistons if the KB's will work?


No way would I go with a set of custom pistons.. why go that way when you bought a set
of inexpensive ones to begin with.. you might end up going .020 over KBs but then
you would need a bore job if the block allows it
wave

Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2806870
08/09/20 01:58 PM
08/09/20 01:58 PM
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Originally Posted by poboyengineering
No, I'm not willing to sacrifice this block on an experiment, hence my question.
I appreciate the advice, but it seems to bring up a couple of more.
Since the block is 4.005, will I be able to get pistons that aren't under 4.000?
Or, since this has 8 sleeves, can they be bored? I don't mind going 4.030 if needed.


Your block is at 4.005 now. With a .02" over piston the bore would need to be enlarged by approximately .015". That's .0075 of material removed from the wall. That's equivalent to two sheets of writing paper. All this assuming you stay with the clearance machined into the new pistons and don't require any additional clearance at 4.02". I highly doubt that .0075" removed from the liners would be too much, but you can always have it checked prior to machining.

Re: Max clearance with hyper pistons 5-.00 [Re: poboyengineering] #2807066
08/09/20 09:30 PM
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madscientist Offline
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Originally Posted by poboyengineering
Originally Posted by 80fbody
Have a short block with similar situation. Thought about having the pistons coated since they are new and came with the shortblock. Likely to crack/collapse the skirts on those style pistons with too much piston slap.


This is what I'm afraid of since they are pretty brittle.This block was from a dirt track racer, and it has 8 sleeves and they measure 4.005, pistons at 3.993. The pistons are new, and the block just needs a quick hone.


Just CALL Line2Line and TALk to them. The coating they make and use is NOT like other coatings. They can easily make up that clearance and the pistons will fit better than if you bought new pistons and sized them.

It’s not like a regular coating. Don’t make this harder than it is.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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