hi inside the piston theres a number386047 cound some one tell me the size of that stock ,10,20 over etc thanks

 

Is it a stock piston your looking at? If it is an off the shelf piston, 99.9% of the time any over size will be noted on the face of the piston with .010, .030, etc. A picture would help determine if it is a stock piston or aftermarket.

 

hi how about the bore being 4.125 which is 4 1/8 right using my whatever its called with the dial gauge then with the tape measure ..on a side note my dog passed on while I was working on the mtr yesterday beside my bed ..I really don't want too work on the mtr now ..but anyhow that is the stock size also cast or molly rings for those pistons there stock just the high comp as my one out of a 2brll 425 are deep these from the starfire are almost flat

 

Sorry about your dog but man this post is hard to read.
Just use a regular iron ring. If' you're just doing a rering then it's probably a waste to use a good moly top ring.

 

That has the right format for an Oldmobile factory part number from the mid-1960s. I don't have a parts book handy, but 386xxx part numbers are from the 19651966 model years. Unfortunately, you'd need a parts book dated around that time to check.

 

from my database:

PISTON, 425 UHC, CR 10.5, ID= one V notch, 0.9" circle
Cast ID 386047 [or 386017]
Dish 2.77 x 0.042"; ~4.15 cc. Comp. Ht=1.615
NOTE: casting ID 386047 documented 7272 as EITHER/OR:
Toro/UHC with circle, Dish = 2.77-2.79 x 0.042-0.047" [~4.2cc]
HC/Non-Toro, no Circle, Dish = 2.83 x 0.065 [~6.7cc]
UHC Dish is SHALLOWER than US Dime [0.054"] is wide.
Toro units often bear BALANCE HOLE in pin boss underside.

To be 100% certain, just apply your Accurate Measuring Device to the piston in your hand, or the bore.

http://www.ebay.com/itm/SHARS-0-6-ST...item45eda2e7d4

 

thank you they do have a circle in middle of piston