XJ6 & XJ12 Series I, II & III 1968-1992

Numbers on chevy piston?

Old 04-28-2019, 12:01 PM
Darrenmb's Avatar
Veteran Member
Thread Starter
Join Date: Oct 2010
Location: Orlando Florida
Posts: 1,715
Received 278 Likes on 182 Posts
Default Numbers on chevy piston?

Anyone tell me what they mean or are they inconsequential???
Also what your take on what looks to be a crack??? Block and crank are off to machine shop next week. (Assuming I can get front hub off) so not too worried about it, but what would have caused it???

First set of numbers
Next set of numbers

A \"b"

The crack right side of left relief
Old 04-28-2019, 02:44 PM
Senior Member
Join Date: Jun 2015
Location: Florida
Posts: 678
Likes: 0
Received 184 Likes on 129 Posts

Looks like the markings of a standard size piston. Bored block pistons will have numbers like 010; 020; 030 indicating that the block was bored to that size.
If the crack is not superficial, I would replace it.
When I did my 350, I ordered all of my engine parts from Summitt Racing.
Since yours is going to a machine shop, they may be able to locate parts cheaper.
Old 04-29-2019, 10:33 AM
LT1 jaguar's Avatar
Join Date: Dec 2018
Location: Wasilla,Alaska
Posts: 77
Received 18 Likes on 13 Posts

I think the "crack" looks odd. It looks more like just a scratch because it ends so abruptly and cleanly at each end. I don't see the "crack" growing into the valve relief, as one would normally. Do you see anything on the under-side of the piston top? See what the machine shop says. I believe the numbers in your 1st photo are related to the manufacturing date of the piston: 11(hr), 21(day), 08(month), 93(year). Also, check the last digits for the OEM replacement piston from Chevrolet. Do they coincide with any of the numbers?
Old 04-30-2019, 11:04 AM
Veteran Member
Join Date: Jul 2012
Location: Walnut Creek, California
Posts: 5,730
Received 1,945 Likes on 1,569 Posts

I suspect that these pistons are just fine for reuse. sourced from a low mileage engine and from a source that had scheduled maintenance.

OTH the machinist can measure and validate them or finds them lacking. Still within "spec, or worn..Diameters. ring land grooves?

Caveat, the pistons must face properly. The relief's match the valve travel, When cold may not "touch"., but when warm the "kiss of death" valve to piston !!! Not me, but close relative!!

Related Topics
Thread Starter
Last Post
Non-Jaguar Vehicles
06-26-2012 12:43 AM
joe cat
XJS ( X27 )
05-04-2008 10:04 AM
joe cat
PRIVATE For Sale / Trade or Buy Classifieds
04-28-2008 12:01 PM
XJ6 & XJ12 Series I, II & III
02-15-2008 07:41 AM
PRIVATE For Sale / Trade or Buy Classifieds
08-09-2006 11:40 PM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Search this Thread
Quick Reply: Numbers on chevy piston?

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
  • Ask a Question
    Get answers from community experts
Question Title:
Your question will be posted in: