cylinder measuring under 66mm?

[Outlawed Genetics]

recently got a spare cyl and when measuring it for a new piston and rings i noticed it was 65.85mm. what am i missing i thought they were all 66mm or above. i measured another stock bore cyl i had laying around and it was exactly 66mm. is this just factory tolerance type thing or whats going on? how do i buy a new piston and rings for it?

 

[FLOTEK]

how are you measuring this bore ? you do realize capliers are only accurate to +or -.002
to an inch right ? you must use a precision bore gauge if you ever expect to get accurate repeatable readings.

 

[Outlawed Genetics]

product info below. as for accuracy they read 66mm on another stock bore multiple times

Kobalt
6" Metric and SAE Caliper

Item #: 293883 Model: 53247
Stainless steel construction for durability
Inch-to-mm conversion button for accurate size readings
Zero setting at any place
Comes with fitted plastic case


Measuring Tool Type: Calipers
Measurement Format: Metric & SAE
Housing Material: Plastic
Measuring Range: 0-6 In.
Accuracy: 0.001 In.

 

[FLOTEK]

calipers are for close reference but not the final word ,they are not a super accurate measuring tool ,i dont care what the rating its listed at ,i own 5 thousand dollars of measureing equipment trust me its only as accurate as the guy using them you can squeeze them hard or soft and get a different readings repeatable accuracy is only about .002 i have been a tool and die maker and built injection molds since 1996 and use these and every other precision inspection tool nearly every day of my life.

 

[dburroug]

thank you flotek...people seem to think that measuring something acurately to the thousandth of an inch is like easy. and even if you do have an amazing set of inside calipers and measure correctly...your still not gonna get a correct answer cuz you will be measuring the very top or bottom rim....which is usually way different size than the rest of the bore. Ever work on an old engine? usually you cant even pull the piston out the top of the block because the top rim doesnt recieve near as much wear creating a ring that is smaller...bore gauge is the way to go and check the service manual...it clearly shows measuring the mid section of the bore not top or bottom

 

[Outlawed Genetics]

no need to be a cocky prick, i simply asked how it could read 66mm every time on one cyl and 65.85 on another every time. even if it isnt super accurate its atleast consistantly giving the same readings. i guess both cylinders are 66mm and the caliper knows the one cyl from the other and is playing a trick on me every time i measure the one in question..

thank you flotek...people seem to think that measuring something acurately to the thousandth of an inch is like easy. and even if you do have an amazing set of inside calipers and measure correctly...your still not gonna get a correct answer cuz you will be measuring the very top or bottom rim....which is usually way different size than the rest of the bore. Ever work on an old engine? usually you cant even pull the piston out the top of the block because the top rim doesnt recieve near as much wear creating a ring that is smaller...bore gauge is the way to go and check the service manual...it clearly shows measuring the mid section of the bore not top or bottom

thanks for the input flotek. im not looking for super accuracy from them, but instead like you say "a close referance" between 2 cylinders that should both be the same and trying to figure out why one is smaller than the other. as long as i can buy a 66mm piston kit and it work i could care less about that 0.15mm difference

 

[dburroug]

wow dude sorry wasnt trying to be cocky or a prick at all...just tryin to help and throw my 2 cents from experience in. my bad man sorry if i offended you. Il just butt out of this one i guess. But you are correct about consistancy even if it is off slightly it is off the same for both, my guess would be the one measuring 66 is actually about a ~66.15 and the 65.85 is actually about a 66...sorry again if i sounded like a jerk...really just tryin to help

 

[Outlawed Genetics]

wow dude sorry wasnt trying to be cocky or a prick at all...just tryin to help and throw my 2 cents from experience in. my bad man sorry if i offended you. Il just butt out of this one i guess. But you are correct about consistancy even if it is off slightly it is off the same for both, my guess would be the one measuring 66 is actually about a ~66.15 and the 65.85 is actually about a 66...sorry again if i sounded like a jerk...really just tryin to help

dont sweat it, i just took you the wrong way. not your fault. its late and im sick and cant sleep. the line i bolded when quoting your last reply is what i was starting to think also. let me also add

we'll lable the cylinders
cyl A this is the one reading 66mm
cyl B this is the one readong 65.85

cyl a is worn and crosshatching isnt very visible some imperfectiongs are visible and this is ready to be sent in for a bore job

cyl b has very low hours (just bought used) and was just freshly honed. even came with stock piston that is in so good of shape that i thought about using it.

i should have added that info sooner and i think we would have came to the bolded conclusion alot sooner.

sorry for being a cranky prick:-[

 

[dburroug]

haha its cool man...sounds like you got a couple jugs there with alot of life left in them...im enjoying a fresh topend right now, but its bittersweet since im at 68mm lol

 

[Outlawed Genetics]

i got a 3rd i gotta rip out of the blasty in my sig tomorow or the day after to measure and either rebuild or replace. i've got 3 motors and 2 blasters so im hoping to freshen 2 of them up and turn the 3rd into a project motor to slowly rip apart and rebuild/add/mod and teach myself a little more about working on them. a good buddy has been helping me alot but theres only so much you can learn by watching someone else.

 

[FLOTEK]

i will add there is a possiblity that the cylinder is slightly less than 66mm ,as long as there are people involved ,mistakes and inaccuracy in the manufacturing process can happen.also i didnt mean to sound objectionable in my posts im just am anal about measuring and want to see you get the correct readings so your on the right path and get the best results

 

[Outlawed Genetics]

thanks for the help.
im looking into piston/ring kits now. got an opinion on vito's forged super stock piston kits? the ones that are supposed to add 5hp?