where is the safe place to grind down a piston.
one of the pistons in a set is 3g heavier than the rest.
npr pistons p73 replacement ones

 

bump

 

It depends on the specific piston design. Since I have never used that brand piston I can't answer your question. You really need to post pictures of inside the piston (underside where the wrist pin goes).

 

its as type-r replacement. identical to oem type-r piston
I looked at them side by side. same thing

 

stock type-r piston nothing special.
anyone?

 

Post a picture of your specific piston and I will tell you. Unless you are saying it is IDENTICAL in every way shape and form as well as ALL holes. There are sometimes balancing holes from the factory depending on manufacturing and this is why I want to see the picture. Not only for that, but I can circle the areas to remove from. I am just trying to help you, but you make things difficult. OR if it's not that important to you then just take it from wherever.

 

U make things complicated like always

Its identical to stock type-r piston . I dont have it with me bro its at work

 

Ok, well I don't have a picture to show you where then. Typically if there is a balancing hole you enlarge that first. If further material is needed then you start to remove it from around the pin bosses. Be sure to shape everything you touch and BREAK ALL EDGES! This is very important to reduce stress risers.

 

pin boss you talking about between pin hole and back of the piston dome? the thick part?


heres a good picture

maybe my oem itr were not actually oem after all.
if these are oem from inline four then mine were aftermarket already also

both of my pistons are identical casting except the Teflon coated area

and both of them don't have dimples on pin boss like the ones in the picture.

3 grams is alot to remove lol I shaved everywhere. and still down to 2 grams I guess I can grind down a lot more where the dimples are on the picture...
all other pistons are exact weight now. they were within one gramm when I got them except this one.(with piston pins)

 

Well, the pin boss is around the pin and will tie into the strutting. You can cut back on the strutting some too. I would take even amounts from all four sides and blend as needed. Definitely weigh as much as possible once you get the idea of how much you are taking off. You can also remove the raised parts where the holes are. Also, all the ribs on the strutting can be removed. I personally don't like touching the crown without a mill.

 

ok that's what I was wondering. I thought those areas are for pin support and cant be too thin

I only got 1g to go so that can be taken care of with those raised parts

where can I remove material from stock itr rods? since im gonna have to weigh those too once the old pistons are pressed out

 

You can start with the casting seams on each side. If you need more than that then it is open for debate and is usually a touchy subject.

 

you mean for rods right?

got the pistons to exact weight with shuffling the pins around.

have to make a connecting rod scale lol. this **** is not as easy at it looks on the internet.

 

Yes for the rods. I already assumed you weighed all pins to see if there were differences. They are almost always the same due to how they are made.

 

Yea pins are slightly different which is good
I used them to get the total weight of the pistons to exactly same on all 4 without trimming too much.