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cylinder bore variation ?

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Old 12-12-2014, 06:26 PM
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Default cylinder bore variation ?

the block I picked up from machine shop I decided to measure.

its been sitting on its side for about a month
fresh bore golden eagle sleeves with cylinder support things in the water jacket. im assuming all GE sleeves have those.

I measured with digital bore gauge.

set it at zero in cylinder#1
cylinder #2 was +.008mm
#3 was zero
#4 was -.008mm

is that acceptable?
is it because its been sitting on the side for few weeks?
Old 12-13-2014, 11:30 PM
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Default Re: cylinder bore variation ?

I measured again heres what I got
dial bore is set at 3.35" with spacers etc ( its a digital gauge)

cyl1-.0229" >>3.3271" >>84.50834mm
cyl2-.02205" >>3.3279" >>84.52866mm
cyl3-.0227" >>3.3273" >>84.51342mm
cyl4-.0232" >>3.3268" >>84.50072mm

I don't know how many decimals do I need to worry about and whats the normal variance if there should be any im not sure.
I just want to check before I order pistons that wont work
Old 12-14-2014, 12:29 AM
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Default Re: cylinder bore variation ?

Down to .0001 is standard for determining the wear in the bore, I don't see anything in that range affecting the engine itself. It is good practice to provide a rotating assembly with pistons or at least the pistons themselves to ensure proper piston to bore clearance. Pistons can vary and this needs to be accounted for in the machining process.
Old 12-14-2014, 05:27 AM
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Default Re: cylinder bore variation ?

Welcome to the real world, most machine shops suck. If you are using cast pistons then there will be some variations in sizes; forged are almost always the same exact size.

Also, HELL NO sitting a block on its side won't distort the bores. That is sig worthy right there LMFAO!
Old 12-14-2014, 06:08 AM
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Default Re: cylinder bore variation ?

yeah .0001 is usually where it comes down to. a ptw of .0011is a big difference from .0019 if you get down to it.


did the pistons go to the machine shop with the block? normally i bring them and say to my machinist i want .xxx piston to wall with these pistons at .xxxx bore. you may either want to bringit back, or grab like a 600 grit flex hone since you already have a gauge and slowly try and even it out, or at least make sure that the smallest cyl is still giving you enough ptw
Old 12-14-2014, 06:16 AM
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Default Re: cylinder bore variation ?

Originally Posted by OneBadTurboCRV
Welcome to the real world, most machine shops suck. If you are using cast pistons then there will be some variations in sizes; forged are almost always the same exact size.

Also, HELL NO sitting a block on its side won't distort the bores. That is sig worthy right there LMFAO!
I agree. Also, The semi/closed decks can have substantial distortion without a deck plate or head on them. The oem open deck has little change.
Old 12-14-2014, 10:21 AM
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Default Re: cylinder bore variation ?

He used deck plate when boring them out
I didnt get pistons yet since i didnt know if its gonna be 84.5 or 85mm after damage is removed
But i think even with this variance its still within limits of wesco or any other pistons so i just need to take it back to machine shop and have him hone the walls to fit the pistons
Old 12-14-2014, 10:23 AM
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Default Re: cylinder bore variation ?

I got all digital measuring tools even though they re from china i think should be ok for home use since they are all auto calibrate
Old 12-15-2014, 06:16 AM
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Default Re: cylinder bore variation ?

its always a good idea to have the pistons with the block when machining or else your just guessing. Every piston varies in size even oem, the only pistons that I have measured that didn't vary were cp's.


Originally Posted by raverx3m
He used deck plate when boring them out
I didnt get pistons yet since i didnt know if its gonna be 84.5 or 85mm after damage is removed
But i think even with this variance its still within limits of wesco or any other pistons so i just need to take it back to machine shop and have him hone the walls to fit the pistons
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