Piston to wall Clearance
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Piston to wall Clearance
i have a question...im getting a set of wiseco 81.5mm pistons and i need to bore and hone my block..my question is..do i get it bored to exactly 81.5 mm which is 3.209 inches??? or do i get it bored larger to accommodate for the piston to wall clearance spec??
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Re: Piston to wall Clearance
If you bored your cylinders to the exactly same size as the piston it wouldnt work lol, your pistons have the recommended p/w clearance right on the sheet inside the box. Depending on your hp goal you increase the clearance from spec to handle the piston expansion.
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Re: Piston to wall Clearance
Depends what the piston spec sheet says, read that before you have the block machined. I had a machine shop make the mistake of mis-reading wiseco's clearances and ruined my block, they made it up buy replacing it though.
Take your advise and do it "right", take everything to the machine shop when your ready
Take your advise and do it "right", take everything to the machine shop when your ready
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Re: Piston to wall Clearance
I ran Wiseco's in my old motor and they recommended them to be run a little tight, I am assuming that is due to the coating on the skirts which wears off.
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Re: Piston to wall Clearance
id like to run them at .003 instead of the recomended .0025...if i do this, then wut do i use as the bore number to put into the equation to achieve my ring gap?
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Re: Piston to wall Clearance
i thought the clearences was in the pistons?..if u had 81.5mm and they called for .0035 that when u honed the cyl to 81.5mm it would have the .0035 clearence???
i might be wrong tho?
i might be wrong tho?
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#8
Re: Piston to wall Clearance
Most of the time you want to run the clearance the mfg. suggest, but if you're throwing big boost on it, then you should go about .0035 - 004.
You can also talk it out with your Engine Builder.
You can also talk it out with your Engine Builder.
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Re: Piston to wall Clearance
ALWAYS have the machine shop check on the actual piston itself on the exact bore. you want to base your calculations from the measurements of the pistons, not from the "number" you think the bore size is. There's always mistakes by machine shops thinking the clearances are already built in to lets say the 3.209/81.5mm or they're not. So to prevent any misunderstandings, make sure just provide the piston when you get the block machined so they can double check and mark the piston to each cylinder.
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Re: Piston to wall Clearance
yea i understand that...but does that mean it has to be bored more than 3.209 and wut about calculating the ring gap? do i use the 3.209 to calculate it, no matter if i decide to use mfg suggestion or if i go all the way up to .005
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Re: Piston to wall Clearance
You can special order file fit rings. The rings on an off the shelf Wiseco box are set up for the bore they recommend (not that they shouldn't be checked).
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Re: Piston to wall Clearance
So how would I find the ring gap? Do I have to actually measure the bore with the dial bore indicator to get the exact bore size? Or can I just use 3.209?
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Re: Piston to wall Clearance
Here dude.... watch all 3 parts.
http://www.youtube.com/watch?v=mpy_By5aIxM
http://www.youtube.com/watch?v=MtTXA9_a8sI
http://www.youtube.com/watch?v=JE7U5l_MoP8&feature=fvst
#17
Re: Piston to wall Clearance
This is some good info since I'm about to do my first build. My machine shop did a hone on my cylinder walls, but I haven't got my pistons yet. The walls looked good enough that they said I could just get by with a hone.
BUT, should I get the 81mm pistons or 81.5mm?? I'm assuming that I need to have the block checked and bored/honed again. But should I assume that the bore now isn't TOO big for the 81mm?? Or do I need to take it by the shop and have the bore checked before I make the order for the pistons??
Not trying to thread jack either, but I just figured it would be relivant.
BUT, should I get the 81mm pistons or 81.5mm?? I'm assuming that I need to have the block checked and bored/honed again. But should I assume that the bore now isn't TOO big for the 81mm?? Or do I need to take it by the shop and have the bore checked before I make the order for the pistons??
Not trying to thread jack either, but I just figured it would be relivant.
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Re: Piston to wall Clearance
You should never do a damn thing until the pistons are in your hand, bottom line.
Ill repeat for you what I and others have repeated for the OP in this thread...
Take the pistons and the block to the machine shop and let them do their job, without measuring nobody can help you... if the shop didnt bore the block it should still be 81mm but with an excessive P/W... this is all speculation of course you shouldnt of had them hone it for no reason without pistons in hand.
Take the block to the expert and let them do their job, thats what you pay them for.
Ill repeat for you what I and others have repeated for the OP in this thread...
Take the pistons and the block to the machine shop and let them do their job, without measuring nobody can help you... if the shop didnt bore the block it should still be 81mm but with an excessive P/W... this is all speculation of course you shouldnt of had them hone it for no reason without pistons in hand.
Take the block to the expert and let them do their job, thats what you pay them for.
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Re: Piston to wall Clearance
Actually the first step IS taking the block to the machine shop to find out if the block needs or has already been bored. From their recommendations you should order pistons and WHEN they arrive the machine shop can measure the pistons and bore or not bore the block.
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Re: Piston to wall Clearance
Actually the first step IS taking the block to the machine shop to find out if the block needs or has already been bored. From their recommendations you should order pistons and WHEN they arrive the machine shop can measure the pistons and bore or not bore the block.
#24
Re: Piston to wall Clearance
You should never do a damn thing until the pistons are in your hand, bottom line.
Ill repeat for you what I and others have repeated for the OP in this thread...
Take the pistons and the block to the machine shop and let them do their job, without measuring nobody can help you... if the shop didnt bore the block it should still be 81mm but with an excessive P/W... this is all speculation of course you shouldnt of had them hone it for no reason without pistons in hand.
Take the block to the expert and let them do their job, thats what you pay them for.
Ill repeat for you what I and others have repeated for the OP in this thread...
Take the pistons and the block to the machine shop and let them do their job, without measuring nobody can help you... if the shop didnt bore the block it should still be 81mm but with an excessive P/W... this is all speculation of course you shouldnt of had them hone it for no reason without pistons in hand.
Take the block to the expert and let them do their job, thats what you pay them for.
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