to overbore or not to over bore... - Page 2 - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Master Chief · 06-24-2008, 05:21 AM

To add to that, from experience, honing for more than 0.03mm-0.04mm, even with a torque plate installed, will cause diferences in the bore diameter, at diferent hights of the cylinder.

Because of the honing machine moving up and down, honing for to long periods (that would be needed to remove more than the 0.04mm material) will cause the middle of the cylinder to be wider than the top, and especially bottom, where the honing machine cant pass thru deep enough.

For best results, honing should be kept to no more the 0.03mm.

(All this depends offcours on what machine, proccess and what stones are used, etc...)

timtiminy · 06-25-2008, 12:35 PM

Quote:

Originally Posted by Master Chief

To add to that, from experience, honing for more than 0.03mm-0.04mm, even with a torque plate installed, will cause diferences in the bore diameter, at diferent hights of the cylinder.

Because of the honing machine moving up and down, honing for to long periods (that would be needed to remove more than the 0.04mm material) will cause the middle of the cylinder to be wider than the top, and especially bottom, where the honing machine cant pass thru deep enough.

For best results, honing should be kept to no more the 0.03mm.

(All this depends offcours on what machine, proccess and what stones are used, etc...)

So you are saying that one should not overbore past .03mm to ensure a consistant bore diameter? then why would you suggest going to an aftermarket piston of 86.5mm. that would mean overboring the cylinder .5mm, that would be overboring almost 17x as big as you recommend. this isnt making sense to me.... anyhow thanks for your advice. I am going to save up till i can get a set of aftermarket forged pistons.

Master Chief · 06-27-2008, 05:10 PM

Boring is one thing, and Honing is a totaly difrent process.
In my last post i was talking about HONING, not BORING !

Its clear that you dont know the difference.
Look up the terms on Google.

I sugset you take the motor to a copetent machine shop, as its obvious you do not have enough knoledge to take matters into your own hand.

Good luck.

timtiminy · 06-28-2008, 05:00 PM

sorry i was confused on the boring/honing i thought you were talking about boring. i understand now. Thanks

timtiminy · 09-09-2008, 12:30 PM

If i am going with aftermarket 86.5mm pistons do i need to take them to the machine shop with me so that they know how large to bore the cylinders with the correct clearance, or do i just have the cylinders bored to 86.5mm and the "86.5mm" pistons are compensating for the clearance by being a little under 86.5mm?

Master Chief · 09-09-2008, 02:20 PM

Take them with you !

The correct proccess is to have the Piston meassured, as per the piston makers instructions, at 20 Deg. C room tmperature - using a micrometer.
Than use the micrometer, fixed at the meassure taken, to zero a bore gauge.

The zeroed bore gauge, should be used to meassure the bore.

The cylinder should be bored, until the bore gauge shows the desired piston to wall clerance (-about 0.03mm honing alowance).

The block offcours, should be at the same room teperature, as the pistons.

It only takes a small error in meassure, or a small temperature difference, to under bore or over bore the block, byond the desired clerances.

Allso, the pistons are not always exactly as advertised, and its smart to have things checked (although i never had a problem with CP's beeing off).

timtiminy · 09-09-2008, 05:10 PM

Thanks master chief. Now the only dilema i have is whether i need to get 87mm pistons in order for the overbore to get rid of the scoring on the cylinder wall... or if 86.5mm pistons will be adequate. what is your expericence with overboring cylinders to clean them up from detonation and blowing a hole through the piston where the ring lands where blown through and the rings gouged into the cylinder wall?

Master Chief · 10-03-2008, 05:01 PM

Thats something that needs to be seen to know.
An experienced machine shop, should be able to determine how much would you need to bore, to clear things up.

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06-24-2008, 05:21 AM	#31
Master Chief Zilvia Junkie Join Date: Feb 2006 Location: Israel Posts: 332 Trader Rating: (3) Feedback Score: 3 reviews	To add to that, from experience, honing for more than 0.03mm-0.04mm, even with a torque plate installed, will cause diferences in the bore diameter, at diferent hights of the cylinder. Because of the honing machine moving up and down, honing for to long periods (that would be needed to remove more than the 0.04mm material) will cause the middle of the cylinder to be wider than the top, and especially bottom, where the honing machine cant pass thru deep enough. For best results, honing should be kept to no more the 0.03mm. (All this depends offcours on what machine, proccess and what stones are used, etc...)

06-27-2008, 05:10 PM	#33
Master Chief Zilvia Junkie Join Date: Feb 2006 Location: Israel Posts: 332 Trader Rating: (3) Feedback Score: 3 reviews	Boring is one thing, and Honing is a totaly difrent process. In my last post i was talking about HONING, not BORING ! Its clear that you dont know the difference. Look up the terms on Google. I sugset you take the motor to a copetent machine shop, as its obvious you do not have enough knoledge to take matters into your own hand. Good luck.

06-28-2008, 05:00 PM	#34
timtiminy Zilvia Addict Join Date: Feb 2006 Location: Socal Posts: 624 Trader Rating: (0) Feedback Score: 0 reviews	sorry i was confused on the boring/honing i thought you were talking about boring. i understand now. Thanks

09-09-2008, 12:30 PM	#35
timtiminy Zilvia Addict Join Date: Feb 2006 Location: Socal Posts: 624 Trader Rating: (0) Feedback Score: 0 reviews	If i am going with aftermarket 86.5mm pistons do i need to take them to the machine shop with me so that they know how large to bore the cylinders with the correct clearance, or do i just have the cylinders bored to 86.5mm and the "86.5mm" pistons are compensating for the clearance by being a little under 86.5mm?

09-09-2008, 02:20 PM	#36
Master Chief Zilvia Junkie Join Date: Feb 2006 Location: Israel Posts: 332 Trader Rating: (3) Feedback Score: 3 reviews	Take them with you ! The correct proccess is to have the Piston meassured, as per the piston makers instructions, at 20 Deg. C room tmperature - using a micrometer. Than use the micrometer, fixed at the meassure taken, to zero a bore gauge. The zeroed bore gauge, should be used to meassure the bore. The cylinder should be bored, until the bore gauge shows the desired piston to wall clerance (-about 0.03mm honing alowance). The block offcours, should be at the same room teperature, as the pistons. It only takes a small error in meassure, or a small temperature difference, to under bore or over bore the block, byond the desired clerances. Allso, the pistons are not always exactly as advertised, and its smart to have things checked (although i never had a problem with CP's beeing off).

09-09-2008, 05:10 PM	#37
timtiminy Zilvia Addict Join Date: Feb 2006 Location: Socal Posts: 624 Trader Rating: (0) Feedback Score: 0 reviews	Thanks master chief. Now the only dilema i have is whether i need to get 87mm pistons in order for the overbore to get rid of the scoring on the cylinder wall... or if 86.5mm pistons will be adequate. what is your expericence with overboring cylinders to clean them up from detonation and blowing a hole through the piston where the ring lands where blown through and the rings gouged into the cylinder wall?

10-03-2008, 05:01 PM	#38
Master Chief Zilvia Junkie Join Date: Feb 2006 Location: Israel Posts: 332 Trader Rating: (3) Feedback Score: 3 reviews	Thats something that needs to be seen to know. An experienced machine shop, should be able to determine how much would you need to bore, to clear things up.