1971 Z28 - Numbers Matching Advice

Discussion in '1970 - 1973 Specific' started by newtodu06, Nov 18, 2019.

  1. newtodu06

    newtodu06 New Member

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    So....here's my problem.
    During the first of July, I purchased a restored '71 Z on eBay from a dealer/shop in New Jersey, and had it shipped to me down in NC. I had seen and heard this car at Carlisle in April 2018, so I wasn't concerned that I didn't need to see it and drive it in July (a big mistake!). I was sold on the pictures, and asked many, many questions before I made the offer and felt fairly confident I was getting a matching numbers car (that's the way it was advertised when I bought it).
    In late July, I noticed I didn't have any top end power (secondaries not opening up), so I took it to a local shop here in NC to look into it. Getting it to the shop was an adventure....it took 30 minutes to travel 5 miles...the lack of power had gotten worse. About a week after they had it, the shop called to say the cam was shot (more than likely it wasn't broken in correctly) and there was metal in the oil. I contacted the original seller to tell them what was happening and they agreed to send me $1000 to have the cam replaced, but that was all they would cover. My current shop was hesitant about just replacing the cam without tearing down the motor to make sure there wasn't anything else going on. That was the only way they would warrant their work. I ok'd the work and the fun began. Tearing it down, they found the cam was bad (not the original), one of the heads was cracked and dated after the build date. It also looks like the pistons, rods and crank are not original.

    So here's my dilemma. If you buy a numbers matching car, and upon further review, the internals (cam, rods, crank, etc) are not original, can you still say it is numbers matching? Furthermore, if the heads contain the GM part number and they are not date correct, can the engine still be regarded as numbers matching?
    In my case, the build date on the TT, and the date stamp on the block, trans and rear end all match. I'll have the work completed, but I'm just wondering how the new parts will affect the value of the car when it comes to selling it.
    Any input would be appreciated.
     
    Last edited: Nov 18, 2019
  2. flht99b

    flht99b Veteran Member

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    Matching numbers implies at least the engine block, transmission case and rear axle housing are original to the car. The heads will need to have date codes close the the block casting date. The internals inside the major components most likely have been replaced as we are talking about a near 50 year old car, things wear out. My 71 Z28 has the warranty replacement short block (original engine blew up under warranty) and original to the car rear axle housing. The Muncie 4speed has been replaced with a Tremec TKO600 5 speed and the rear now has a new Eaton posi unit (original posi case cracked) and 4.10 GM gears (car was born with 3.73's). So my car isn't a "matching numbers" car. Correct carburetor, alternator, distributor, water pump, pulley's, etc are parts often mentioned in the same sentence as a matching number correct to 1971 car.
     
  3. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    This will be an interesting thread to watch for opinions.

    My opinion, take it for what its worth, is the internals of an engine are wear items that for the most part can and should be replaced when they are end of life. When they are replaced, again, my opinion, replace them where necessary with at least stock or better level components for durability. Keep the intent to duplicate the same performance-feel of the original build but increase the durability to the extent you can afford. I know there are some very differing opinions here and many would say you have to use NOS GM parts but at least for me that's beyond the scope of my particular build. I would rather build in more durability to protect the original block and heads than to use 50 year old reconditioned used parts or spend triple the amount for NOS parts when they can be found. Some cars it may be worth it like a Yenko or an L-88 'vette.

    For the heads, it is generally considered to be a "correct" numbers restoration to have the heads numbers pre-date the build of the car based on the Trim Tag date by as little as a week to as much as a couple months, but there are no hard and fast rules here (at least not that I am aware of.) They definitely can't be dated after the car's build date unless you have some kind of evidence of the original owner receiving the car without the heads.:screwup:

    The block is VIN stamped so if the original is gone, then it will never truly be able to be "numbers matching" again. A word on this. "Numbers matching" has really become bastardized in the last 10 years or so to mean essentially nothing in this hobby. "Born with" is perhaps a better term to mean it has the components that the car rolled of the assembly line with.
     
    Last edited: Nov 18, 2019
    Dave Nelson likes this.
  4. Gary S

    Gary S Administrator Lifetime Gold Member

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    I would agree with that. To be called numbers matching, the three major drivetrain components should be original. Other than that, you have to expect the car to have major repairs and rebuilds in mechanical parts over 50 years. The same could be said for the interior and trim parts. They wear out and need replacing.

    I would call your '71 Z28 numbers matching. If you want completely original, the search gets a lot longer finding a car that is around 100% original, and before buying a car like that, plan to spend days inspecting every detail of the car or you will still be disappointed.
     
  5. newtodu06

    newtodu06 New Member

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    I agree with the internal parts wear out over time and they should be replaced with better, durable, current parts, so I’m cool with that. As far as the head goes, I’d like it to pre date the build Date, but if it doesn’t, I can explain it, if necessary.
     
  6. mallard

    mallard Veteran Member

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    My 74 has the "born with" differential, housing although the gears have been changed, T10 transmission and numbers matching engine block but a previous owner had the engine rebuilt and it has 1970 LT1 heads. I just make sure when I'm "advertising" it I'm clear that it has numbers matching L82 engine block. When you get inside I don't know how anyone could be held accountable for "innards" that aren't original.
     
  7. 2ndGenCrazy

    2ndGenCrazy Veteran Member

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    There is "numbers matching" and "born with". Not too many born with left out there.
     
  8. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Hindsight is always 20-20, but next time and for others reading this, define in detail in writing to the seller what "numbers matching" means to you and have the seller sign a statement that the car you are buying conforms to this definition. If they balk at signing, you have your answer on that car.
     
  9. Vettenick

    Vettenick Vettenick

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    I feel for you. Well, look what you got with a numbers matching situation. IMHO. an engine that was improperly done.
    If the block, most important is in tact. I would say get it rebuilt with as many GM parts available. Just be aware that if they deck the block, they might eliminate the engine stampings.
     
  10. COPO

    COPO Veteran Member Lifetime Gold Member

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    Today’s machine shops can skim the deck and go around the stamped numbers. If they say they can’t, then find another shop.
     

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