Numbers matching; how far can I go

[try2pas]

I have a numbers matching '72. The engine is tired. How far can I go in repairing and boosting HP? Like going a 383 and or different cam etc. Still matching numbers but different internals. How far can I go? What about just taking out the engine and putting something else in there and then when I sell it putting the original engine back in? What can I or can't I do that won't detract from an original "matching numbers '72 corvette"?

 

[Vettehead Mikey]

There must at least two dozen definitions of 'numbers matching', each claiming to be the correct one. I'd suggest you determine which one is your favourite and modify accordingly. I'd guess that my definition is much much stricter than yours and most people in the hobby.

 

[6880 Mike]

I agree with Mikey; what you do is up to you. I get the impression you already know what your limits might be.

 

[Peer81]

First find out how numbers matching your vette really is. If the NCRS is happy with your car at a base level then take out the engine put it in a corner and get orbuild yourself a new 383. Original applies only ones is my idea so the engine in the corner is of value as it is!
If the NCRS thinks the car needs a lot to come close to matching something then it doesn't matter anyway.
Good luck with your options

Greetings Peter

 

[Mac]

First find out how numbers matching your vette really is. If the NCRS is happy with your car at a base level then take out the engine put it in a corner and get orbuild yourself a new 383. Original applies only ones is my idea so the engine in the corner is of value as it is!
If the NCRS thinks the car needs a lot to come close to matching something then it doesn't matter anyway.
Good luck with your options

Greetings Peter

Well said, Peter.

Mac

 

[Vettehead Mikey]

First find out how numbers matching your vette really is. If the NCRS is happy with your car at a base level then take out the engine put it in a corner and get orbuild yourself a new 383. Original applies only ones is my idea so the engine in the corner is of value as it is!
If the NCRS thinks the car needs a lot to come close to matching something then it doesn't matter anyway.
Good luck with your options

Greetings Peter

NCRS has no definition of matching numbers and avoids the term at all costs because of it's ambiguity. NCRS also does not verify whether a component is the 'born-with factory original', contrary to popular belief. This includes the engine and it's precious stamp pad.

 

[kpic]

try2pas
http://www.ncrs.org/ | Judging Score Sheets

Their score sheets are online.

For example:
"A. Casting number & case configuration (If incorrect, deduct 350 & do not judge or score B, C, or D below)"

I doubt losing 350 points wouldn't be missed.

Hope this helps answer your questions.

 

[6880 Mike]

This thread is not about the NCRS. The OP asked only about matching numbers.

 

[Vettehead Mikey]

This thread is not about the NCRS. The OP asked only about matching numbers.

Exactly and following the OP's request strictly for 'matching numbers':

try2pas
http://www.ncrs.org/ | Judging Score Sheets

Their score sheets are online.

For example:
"A. Casting number & case configuration (If incorrect, deduct 350 & do not judge or score B, C, or D below)"

I doubt losing 350 points wouldn't be missed.

Hope this helps answer your questions.

The OP's car originally came with a Flint MI cast 3970010 engine block. GM made literally tens of millions with that casting number. They're not unique to Corvettes in any way. The engine in the OP's car now might actually be from Grannie's old station wagon but would probably have the correct casting number and case configuration. It would therefore receive no deduct.

Does that mean it's matching numbers? :eyerole

It's a huge but common error to use NCRS judging in determining if a car is 'original' or 'authentic'. A car can have an obviously non-original engine and still get the top award.

 

[Peer81]

That is why i stay as far away from any organisation or numbers judge as i can. So sorry for the mixup and the topic detour. But back on topic.

Then the question is really simple. If numbers matching only adds value through the eyes of the beholder then you can keep it OEM looking on the outside and try to change stuff inside. Problem is with the torque and hp numbers we are used to today quickly you run into the limitation of the original engines "skin" like the exhaust. Nowadays you have to question yourself if you still want to build and maintain an engine with hydraulic non roller camshaft (i don't!). So take the old one out and get yourself a nice new crate engine or something.
Good luck,

Greetings Peter

 

[Vettehead Mikey]

Peter- not your fault.

The problem is that the question is essentially unanswerable. There's no set definition of the term 'numbers matching' any more than there's a set answer to the question 'how far is up?'. Even if the OP were to state his precise definition, it's unlikely that a potential observer or purchaser would have the same one.

Much like the terms 'all original', 'no-hit body', 'fully restored', 'original miles' and the contradictory 'restored to original', the words 'numbers matching' are now just an overused buzz phrase that make my eyes glaze over.

 

[kpic]

Exactly and following the OP's request strictly for 'matching numbers':



The OP's car originally came with a Flint MI cast 3970010 engine block. GM made literally tens of millions with that casting number. They're not unique to Corvettes in any way. The engine in the OP's car now might actually be from Grannie's old station wagon but would probably have the correct casting number and case configuration. It would therefore receive no deduct.

Does that mean it's matching numbers? :eyerole

It's a huge but common error to use NCRS judging in determining if a car is 'original' or 'authentic'. A car can have an obviously non-original engine and still get the top award.

The 1972 had either a 3970010 or 3970014, correct? At least Mike Antonick's book says so.

Casting PNs are typically the same in any given family, correct? I've read decoding 350 casting numbers is practically useless as GM used the 3970010 as a basis for many engines.

How to decode Chevy Engine Codes Pretty interesting reading.

"Numbers Matching"
This is my opinion, and the generally accepted norm:
When people say "It's numbers matching" - what they mean is the engine (or other component, i.e the transmission) can be MATCHED to the vehicle it was originally used in. This match is done via the PARTIAL VIN stamp on the component. The partial VIN will match the vehicles VIN. If it does - it's "numbers matching", otherwise - it's not. done. end of story.
Some folks use these terms loosely, or will say "numbers correct" or something to that effect. But numbers correct is not numbers matching. Again, it either matches or it doesn't. If it doesn't match - is it correct?
Numbers matching is important when you're trying to decode a Z28 or Super Sport where the VIN won't identify the vehicle as such. You need to decode the engine and see if it matches the vehicle, and if the code signifies Z28 or SS equipment.
Lastly, in extreme cases, you'll want to verify the numbers stamped onto the component were the ones stamped into it originally and aren't restamped.
The point of this article is to help you figure out how to decode stuff.
Small Block Chevy Engine Block casting and code identification

How to decode Chevy Engine Codes

I always thought there was a little machined pad on the block which clarified matters. Learn something everyday, I guess. Thanks for the clarification.

 

[Vettehead Mikey]

The 1972 had either a 3970010 or 3970014, correct? At least Mike Antonick's book says so.

Very, very few had a 3970014 block. Maybe a handful. Those were cast at the Tonawanda plant and sent to Flint for final machining and assembly to ensure compatibility between the two plants. I've never personally seen one in a'72.

I always thought there was a little machined pad on the block which clarified matters. Learn something everyday, I guess. Thanks for the clarification.

There is and the judges do look at them in NCRS judging albeit no attempt to authenticate or certify is made. To minimize the temptation by otherwise honest people to counterfeit, only a token amount of points is assigned. For comparison, a cigar lighter that functions correctly carries the same amount of points as correct looking VIN derivative on the pad. A non-original pad or one that is blank on an otherwise correct engine takes only a minor hit.

The link you provided is strictly the opinion of the author of that site and mentions only the engine block. There's other components that carry a VIN derivative and hundreds of other components that carry some sort of numbers that would identify them as being original. How many must match and who controls the list for pass/fail?

What about paint and interior colour matching the trim tag?

What about verifying which options the car did/did not come from the factory with? If an owner adds power steering is the car 'numbers matching'?

 

[kpic]

What you and I are saying are strictly opinions also, correct?

 

[Vettehead Mikey]

If you mean that an individual might have an opinion on the subject and that it might differ from someone else, I suppose that's possible.

As for my opinion as to the correct definition of 'numbers matching', I have none and simply avoid using the term.