Numbers Matching?

[80VetteL82]

Where on my 1980 L82 would I find the numbers to tell if its #'s matching? Also, I was planning on buying a rebuilt rearend from ecklers, so I would have to send my OE differential in as a core. Do people look for an OE differential when looking for a #'s matching car?

Thanks,
80VetteL82
:cool

 

[srs244]

not to be vague, but the definition of numbers matching takes all types of twists and turns. the most liberal would be the entire drive train from front to rear (in my opinion anyway) so that would include the original, date coded engine parts and number pad stamping on the block, correct trans and rear end. all these are coded. of course the rear and trans could be replaced with similar date coded stuff, but the block and the stamp pad with the vin number on it would appear to be overstamped if altered (although there are those out there that are grinding the pad down and restamping to look original).

a good place to start would be to go to the NCRS website and get a copy of their judging specs. that would be the definitive answer to your question.

steve

 

[red70vette]

A true numbers matching car has the original drive train(Engine, Trans, Rear end) with all the numbers and dates intact and all other dated and coded parts with correct dates and codes. The thought being that all of the parts look like the day it came from the factory with the proper part numbers and dates. The NCRS puts out a book with all the acceptable codes and dates for these parts(the C3 specifications book is 168 pages long). They include but are not limited to plug wires, alternator, horns, starter, headlamps, exhaust manifolds, heads, intakes, carburateors, glass, and on and on and on.

That is what a numbers matching car means to a purist. Some people think if the Vin number matches the title it is a numbers matching car(some cars don"t???). It's all a matter of opinion.

 

[Erik S. Klein]

Start with the stamp pad on your block. There should be two numbers there - one identifies the engine type and the other is a portion of your VIN. If those match you've at least got the start of a numbers-matching car. The rest of the parts, as mentioned above, are date coded not VIN encoded so you can buy replacements.

 

[80VetteL82]

great thanks for the info.
80VetteL82

 

[mvftw]

Only the engine & transmission will have the vin serial number on it. Every other part will have a part number & date code. This book will tell you everything you need to know about number matching...
http://www.amazon.com/gp/product/0760306575/qid=1146070973/sr=1-4/ref=sr_1_4/002-7122670-7376825?s=books&v=glance&n=283155

 

[huk_finn]

Start with the stamp pad on your block. There should be two numbers there - one identifies the engine type and the other is a portion of your VIN. If those match you've at least got the start of a numbers-matching car. The rest of the parts, as mentioned above, are date coded not VIN encoded so you can buy replacements.

heres something I found out about the engine pad. G.M. used an 18 inch ( i think it was that size) grinding ( for lack of better name) wheel to deck the factory blocks. Normal guys who deck blocks and restamp use somewhere around an 8 -10 inch cutter. So someone who KNOWS will be able to (probably use microscope) will be able to tell the difference in grinding arcs/marks.

 

[Vettehead Mikey]

heres something I found out about the engine pad. G.M. used an 18 inch ( i think it was that size) grinding ( for lack of better name) wheel to deck the factory blocks

Not sure where you got that info, but it's incorrect. No cutting 'wheels' or rotary machinery of any type was used at GM.

The actual machine and process name was a 'broaching' machine in which a cutting tool resembling a 40' long coarse file was dragged longitudinally along the block surfaces. This process is what caused the faint parallel lines and grooves (broach marks) on the cylinder head mounting surface and is what people look for when trying to determine in an engine has been restamped or not.

The rotary machines that rebuild shops use leave a diagonal series of sweeping lines on the surface

 

[JohnZ]

Here's a photo of the innards of the broach used at Flint V-8 and Tonawanda; the machine was about the size of a bus. The block was pushed upside-down through the broach on the left that did the pan rails and upper half of the main journal bores, then was flipped over and pushed through the broach on the right, which did the decks and front/rear manifold seal surfaces. As Mike said, no rotary cutters of any kind were ever used for decks in Chevrolet engine plants.

 

[huk_finn]

vettehead &johnz,, thanks for clearing that up & the pic. Got that info from a restorer in illinois. I'll take your word on it instead of his. Could there have been a change in machinery during the years? Or from different plants?
That came up while discussing the possibility of decking the block and saving the number pad on a 73 454

 

[JohnZ]

vettehead &johnz,, thanks for clearing that up & the pic. Got that info from a restorer in illinois. I'll take your word on it instead of his. Could there have been a change in machinery during the years? Or from different plants?
That came up while discussing the possibility of decking the block and saving the number pad on a 73 454

Nope, no exceptions for original Chevrolet production blocks - all were run through a linear broach. Rotary cutters are only used in rebuild shops and machine shops; Flint V-8 and Tonawanda each built an engine every twelve seconds, and the broach was the only machining process that was viable at a production rate of 300 per hour.