Wiseco piston installation questions

[Walleye]

I just got 65mm wiseco pistons, and im a 3rd year machinist at my college, and i am boring the sleeves then hone it to install wiseco pistons.

 

the problem is that i measured the ring clearance, and bored to that spec and left .0005th out for honing. It fits fine but not entirely, just only 1/4 of the top fits, the bottom of the piston will not fit. i measured the piston, and it is from the top to bottom, .014 inches difference!!! wtf. is that normal or not? if not so will wiseco replace the pistons even though i installed the rings on already?

Edited April 7, 2006 by Walleye

[Fastrat]

If I remember correctly, this is normal. Wiseco does this to offset the difference in thermal expansion between the top and bottom of the piston. I'm not exactly sure what you mean by "the bottom doesn't fit" though.

[Master of Faster]

Where exactly did you measure the piston at? The ring land area is smaller than the skirt of the piston. If you measured the skirt on the bottom and the very top by the rings then that would account for the huge difference (.014") in size. When you measure the piston to find the dimension you need to bore to, you need to measure the skirt and then add .003" for piston/cylinder clearance. Like you already said it is smart to bore a little small and hone to size to get rid of the bore bar marks.

Edited April 7, 2006 by Master of Faster

[fastbanshee4u]

Yes ,this is normal.Measure the bottom of the piston,then go by Wiseco clearance specs.Best ofall to you and other people,call the manufacture first.

[Master of Faster]

I understand the top of the piston expanding further but don't you guys think that .014" is a little excessive? Thats why I was asking him where he measured, I don't know but I just thought it was alot of variance.

[PassionRE]

The ring part # is the reccomended finish bore size. You should have 513MO6500's for 65mm bore...ring part #2559CD the 2559 stands for 2.559" finish bore size. If you want a ultra precision fit, measure the piston at the furthest down area of the piston skirt that can be measured and then add .003" to that number for reccomended finish bore spec. I personally set them up at .0035" clearance.. Also..... use a calibrated dial bore gauge to check this , telescoping gauges are a complete waste of time...Jim

Edited April 7, 2006 by PassionRE

[Walleye]

Thanks guys

 

yes i measured it at the very top of the piston, and then measured the bottom of the skirt, and thats .014" difference.

 

I did some calculations last night, and the overall total bore i need to bore to is 65.006mm which is 2.559" so it all makes sense now. i realized that the piston will expand when it gets hot, and the top part of the piston is the hottest part of the piston.

 

to that guy who asked about the bottom of the piston would not fit is that i tried to see how much room there would be when i try to put the piston in by the bottom of the skirt in first. thats what i meant by.

 

I will go ahead today and bore it to 2.5585" and leave out .0005 for honing.

 

a machine shop told me that if its a steel ring, i am okay to use 280grit stone as wiseco states on their manual. but he said that if its a moly ring, then i am to use 525 stone. I'm not sure if my rings are moly or steel... it came with the piston kit.

 

He also said that if i use 280 stone, i am to leave .001 for honing, if i am to use 525 stone, i have to leave up to .0005" for honing.

 

and yes i use precison tools, i do have dial bore gauge.

 

i will recheck ring part number and see if it is 2.559.