how do you measure piston size in a cylinder?

[caseywoods5]

i got a cylinder and head for free off of one of my buddies with a blaster. he had one with no damages and one that had broken the rings and was in need of a bore. he gave me the one with no damages and it had a new gasket and new washers on the nuts but was missing one nut. how can i measure the cylinder to see what size piston it takes? because if it has a bigger one than what my blasty has i am going to buy a piston and swap them.I:I

 

[Whitty21]

i am getting the impression you believe the a stock cylinder bored more makes power difference, which it doenst really. but to measure it get a micrometer that can read inside and outside diameter, it is a must for rebuilding an engine

 

[scotj77]

send it to ken and get it bored and ported if you want more power a bigger piston is not going to give you any noticable difference. a port job will give you tons of power gains. contact kenoconnorracing.com

 

[caseywoods5]

i am getting the impression you believe the a stock cylinder bored more makes power difference, which it doenst really. but to measure it get a micrometer that can read inside and outside diameter, it is a must for rebuilding an engine

is there any other way? i don't have a micrometer:-/

 

[scotj77]

take it to a machine shop they will measure it for you. a micrometer is the only way to measure the bore size correctly

 

[caseywoods5]

send it to ken and get it bored and ported if you want more power a bigger piston is not going to give you any noticable difference. a port job will give you tons of power gains. contact kenoconnorracing.com

i'll check out his site, thanks man. rep given

 

[Whitty21]

nope, not with any accuracy, you can get them for 6 bucks at some places, but if u dont know how to use a standard one i suggest getting a digital one,

here...... http://www.princessauto.com/worksho...precision-measuring/8321069-4-digital-caliper

 

[caseywoods5]

rep given to you as well whitty. thanks.

 

[scotj77]

back at ya. 15151515

 

[phragle]

you can use a tapemeasure, but you have to have REALLY REALLY good eyes. When the lines get down past 1/8th (0.125)of an inch they start looking fuzzy to my old eyes, and you need to see those little lines down to 0.001 of an inch so you can get the clearances right. The clearance should be around 0.003 +/- depending on use. TRy googling the thickness os a human hair in inches.

Doing it correctly, the piston is bought in the correct bore size, the cylinder is actually bored slightly undersized and then the cylinder is honed to tolerance.

 

[caseywoods5]

thanks ALOT man. godfather saved the day and saved me money can't give rep just yet but i'll give you rep tomorrow when it lets me!

 

[Whitty21]

as smart as godfather is, i still recomend the caliper, not only is there flaws in your eyes, but also the tape, you can always use a caliper anyways, just my .02

 

[scotj77]

omg... pretty sure he was f'n with ya about the tape measure. no tape measure i have ever had had marks smaller than 1/32. take it to a shop and they will measure it for free

 

[phragle]

The tape measure was a metaphore to the accuracy needed.

The godfather does not need rep. He enjoys helping those that are trying to help themselves. You came upon the board with a very specific question which shows that you are thinking. Had you come on here and asked what size piston do you need when your cylinder is as big around as a coffee cup, I would have told you to drill a wristpin hole in a can of refried beans. Get yourself a set of 15 dollar digital calipers from harbor frieght. you wont be able to set up a cylinder with them, but they will be accurate enough to determine what bore the cylinder is on. stock is 66mm. the calipers will switch display readouts between english and metric and you will find them a very handy tool to have floating around the garage.

 

[Whitty21]

lol i didn't catch the common phragle sarcasim there lol, i thought he was maybe drunk lol, nice touch with the bean can godfather lolol

 

[brandoz28]

yeah, the cylinder to wall clearance is only .003....which is roughly half as thick as a human hair

 

[caseywoods5]

daggone man half as thick as human hair is little! and the godfather had my hopes up that i wouldn't have to buy a caliper. and the link that showed the caliper said they were out of stock. also godfather if you don't mind me asking, how long have you been working on blasters and what is the greatest amount of horsepower that you have squeezed out of them?

 

[caseywoods5]

also thanks again godfather

 

[ricekiller1985]

harbor freight is the easiest place to get the calipers I finally picked up a set on friday and they have come in handy with things I didn't think I was even going to need them for

 

[phragle]

not sure of horsepower... going to shoot for 45~50 this comming spring.

As for blasters, I raced and wrenched on my first one in spring of 1988, early in the first year of production.