KB Pistons. Can I mill a dish in the flat tops?

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KB Pistons. Can I mill a dish in the flat tops?

Post  512Fairlane on February 9th 2012, 11:36 pm

I'm turning a bracket motor into a street motor and it has Keith Black flat top Hypereutectic pistons in it. With the Dove heads it has around 11.5:1 compression. Its still assembled so I can't see the pistons. Does anyone know if the top of the piston has enough thickness that I could mill a dish in them? Or do you think I could run that much compression on 93 octane pump gas? I polished the combustion chambers in the heads and it has some mild porting on the exhaust side. This is a budget driver so I'm trying to keep the costs down (and I'm a cheap a#@). The cam specs are in another post below this one.
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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  LivermoreDave on February 9th 2012, 11:49 pm

Don't quote me but KB pistons that you mention use a "fire ring" design. That being said (wrote), the deck should be rather thick. Although you may lose a bit of quench, I would put the piston in a lathe or mill and flat top it the amount you need to realize the compression you seek.

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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  512Fairlane on February 9th 2012, 11:57 pm

I believe we decked the block so the pistons were very close to 0 deck. I would like to keep the quench area at zero but mill a dish similar to the combustion chamber shape in the top of the piston. Would this be feasible or should I just buy the dished pistons?
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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  cool40 on February 10th 2012, 12:14 am

buy some pistons and sell the kb's.JMO Very Happy
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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  dfree383 on February 10th 2012, 1:43 am

I'm with cool, just get a new set in what you need, they are not expensive.

I'd be concerned with getting to thin in a hyper piston, they shatter to easy untouched.
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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  dave d on February 10th 2012, 9:44 am

I'm running that much compression in my street motor,I do keep some race fuel around just to add a little in to bump up octane but not all the time,really never experienced any problems running c-9 heads which are the same as doves and I do have hardend seats from different post.Hope this helps. My pistons are forged


Last edited by dave d on February 10th 2012, 9:45 am; edited 1 time in total (Reason for editing : added text)
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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  quick 52 on February 10th 2012, 10:36 am

i would get new kb pistons in 15cc or 22cc dish to replace and lower comp. i use the 22cc dish and the the dish is around .180 deep to rework yours would take milling and would cost $$$ you could use for new

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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  Tore on February 10th 2012, 12:41 pm

I am going thru the same thing but I am putting an .080 thick hrad gasket on to lower the compression.


Tore
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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  512Fairlane on February 10th 2012, 2:11 pm

Tore wrote:I am going thru the same thing but I am putting an .080 thick hrad gasket on to lower the compression.


Tore

I was wondering if that might be an option. My rotating assembly was balanced when we built this motor 16 or 17 years ago. I hate to have to redo all of that if the shortblock still looks good. This motor had around 500 passes on it but it wasn't abused so I'm hoping everything inside is still in decent shape.
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Re: KB Pistons. Can I mill a dish in the flat tops?

Post  Paul Kane on February 10th 2012, 8:58 pm

512Fairlane wrote: My rotating assembly was balanced when we built this motor 16 or 17 years ago. I hate to have to redo all of that if the shortblock still looks good.
If you are worried about having to rebalance because you changed your flat tops to dish tops, then consider that you would need to rebalance either way. Once you machine enough dish into your flat tops, you will have changed the bob wieght of your rotating assmmbly enough that a rebalance is in order anyway. Further, I'll venture to guess that 22cc dish top KBs will be closer to your original bob weight than your current flat top KBs will be with the 22cc dishes machined into them.

And the cost of the new pistons versus the time and labor to machine the flat tops is a wash.

Paul


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