Piston Question

[nick77]

Hi everyone

Im new to the import scence and the metric convertions

I know that on a standard run of the mill ford 302 that if its bored out .030 the top of the piston will have 030 cast in the top of the piston

 

Problem i ran into was that when i pulled my 77 280z engine apart to re-ring it 2 of the pistons had a 2 and a smaller 5 and the other 4 had a 4 and a smaller 5 now if my math serves me right and the 2 5 means .25mm thats a .010 oversize, i have never heard of a .010 oversize and the engine had around 130,000 miles on it when it was rebuilt and theres no way that it could be bored out only 10thou

 

I was just wondering what the numbers on the top mean and if i should be alarmed that they are not all the same?

 

Thanks Guys

Nick

 

PS I Have Searched This Topic

[jc052685]

Hi everyone

Im new to the import scence and the metric convertions

I know that on a standard run of the mill ford 302 that if its bored out .030 the top of the piston will have 030 cast in the top of the piston

 

Problem i ran into was that when i pulled my 77 280z engine apart to re-ring it 2 of the pistons had a 2 and a smaller 5 and the other 4 had a 4 and a smaller 5 now if my math serves me right and the 2 5 means .25mm thats a .010 oversize, i have never heard of a .010 oversize and the engine had around 130,000 miles on it when it was rebuilt and theres no way that it could be bored out only 10thou

 

I was just wondering what the numbers on the top mean and if i should be alarmed that they are not all the same?

 

Thanks Guys

Nick

 

PS I Have Searched This Topic

 

just because the motor has some miles on it does not mean that it would need more than a .010 overbore. Maybe try using some micrometers.

[josh817]

Digital calipers. :]

 

And no I don't think so. Why don't you do the proper thing and gap all your rings. Note which cylinders have odd gaps, and then see if it corresponds with the piston and its number.

 

When I say "the right thing" I mean setting your ring gap, not trolling you. :] But hey! Thats a pretty good sign if you can read the tops of the pistons when you took them out! Unless you wire brushed them.