Re: Cylinder bore question
[Re: The Sphinx]
#2405608
11/18/17 07:52 PM
11/18/17 07:52 PM
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Joined: Jan 2011
Posts: 4,785 Utah and Alaska
astjp2
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master
Joined: Jan 2011
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Utah and Alaska
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Hyper's are a much tighter bore than forged pistons. You should be able to hone for your new pistons. Tim
1941 Taylorcraft 1968 Charger 1994 Wrangler 1998 Wrangler 2008 Kia Rio 2017 Jetta
I didn't do 4 years and 9 months of Graduate School to be called Mister!
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Re: Cylinder bore question
[Re: The Sphinx]
#2405760
11/19/17 01:27 AM
11/19/17 01:27 AM
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Joined: Aug 2003
Posts: 43,303 Bend,OR USA
Cab_Burge
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The clearances are usually made on the pistons to fit a certain size overbore, example the forged Icon piston from KB would be around 4.4440 to 4.4460 for a 4.350 bore while the same size hypereutectic might be from 4.4978 to 4.4980 They would both have the proper clearances that KB would want for that size bore On your deal I would order a set of pistons and rods and measure them before deciding to keep and use them, if they clearances are to much send them back and go to the next size over bore BTW, you can order a custom set of pistons in any size you want, IE, for 4.4530 to 4.4590 instead of going to 4.460
Last edited by Cab_Burge; 11/19/17 01:30 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Cylinder bore question
[Re: Cab_Burge]
#2405872
11/19/17 11:56 AM
11/19/17 11:56 AM
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Joined: May 2005
Posts: 2,009 Apollo, PA.
B1MAXX
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The clearances are usually made on the pistons to fit a certain size overbore, example the forged Icon piston from KB would be around 4.4440 to 4.4460 for a 4.350 bore while the same size hypereutectic might be from 4.4978 to 4.4980 think you meant 4.34xx should be ok to hone for forged. If you were going the other way ....that would be a problem.
Last edited by B1MAXX; 11/19/17 11:59 AM.
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Re: Cylinder bore question
[Re: B1MAXX]
#2405883
11/19/17 12:24 PM
11/19/17 12:24 PM
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Joined: May 2005
Posts: 2,009 Apollo, PA.
B1MAXX
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I's this a fresh eng. that was never fired?
bottom line is: generally stock cast piston installed .001-.002 hypereutectic cast .0015-.0045 forged .0035-.007
You would have to have the known current bore size current and condition. then measure the forged pistons to know how much margin you have to play with.
Last edited by B1MAXX; 11/19/17 12:25 PM.
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Re: Cylinder bore question
[Re: B1MAXX]
#2406553
11/20/17 10:33 PM
11/20/17 10:33 PM
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Joined: Aug 2003
Posts: 43,303 Bend,OR USA
Cab_Burge
I Win
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I Win
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Bend,OR USA
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The clearances are usually made on the pistons to fit a certain size overbore, example the forged Icon piston from KB would be around 4.4440 to 4.4460 for a 4.350 bore while the same size hypereutectic might be from 4.4978 to 4.4980 think you meant 4.34xx should be ok to hone for forged. If you were going the other way ....that would be a problem. You are correct I was trying to use the stock 340 bore size, 4.040 I need to proof read my posts better
Last edited by Cab_Burge; 11/20/17 10:35 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Cylinder bore question
[Re: B1MAXX]
#2407468
11/22/17 05:39 PM
11/22/17 05:39 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
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I've never heard that one before and I've been into engines since the '60s.
Spend a couple of hours going through piston manufacturers' websites and you'll see they differentiate clearance by piston material(s).
Mahle has been doing a lot of work on steel pistons (not cast iron) because the coefficients of linear expansion are so close they can run tighter piston to wall clearances for better ring seal. Once again the piston material determines piston to wall clearance. Interestingly Smokey Yunick mentioned steel pistons as something worth looking into about 20 years ago. Steel has much higher hot strength which could be useful in some applications.
R.
Last edited by dogdays; 11/22/17 05:40 PM.
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Re: Cylinder bore question
[Re: dogdays]
#2407828
11/23/17 01:36 PM
11/23/17 01:36 PM
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Joined: May 2005
Posts: 2,009 Apollo, PA.
B1MAXX
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from a 21 year old speed pro catalog. Not denying material is a factor also.
Last edited by B1MAXX; 11/23/17 01:38 PM.
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Re: Cylinder bore question
[Re: dogdays]
#2408623
11/25/17 12:54 PM
11/25/17 12:54 PM
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Joined: May 2005
Posts: 2,009 Apollo, PA.
B1MAXX
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It's all good I believe for instance that the reason for running a factory cast piston so tight as opposed to a forged one set up loose is mainly in the design parameters. One of which is material. Some good reads. http://blog.jepistons.com/understanding-piston-skirt-designhttp://www.enginebuildermag.com/ from this article "Some people think that the same thermal characteristics that allow forged pistons to run cooler also causes them to swell more as they heat up. Consequently, there’s a common misconception that forged pistons always require greater skirt-to-wall clearances. This is a notion that isn’t necessarily true because clearances depend on the type of alloy that’s used in a forged piston, the design of the piston itself and the application in which the piston will be used. [/b]Some forged alloys actually have a lower coefficient of thermal expansion than the alloys commonly used in conventional cast pistons!"[b][/b] If a forged alloy expands less why would we run it looser. For performance reasons, which requires a skirt redesign.
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