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1966 Corvette L72 427/425

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This neat Corvette coupe has an equally neat story. We acquired it from a gentleman who bought it at a sheriff's sale in 1992. It had been pulled out of a garage behind a foreclosed house in downtown Cleveland. He didn't pay much for it and he said it was covered with about an inch of dust. He took it home, cleaned it up, tuned it up, and drove it for the next 20-something years. During that time, he changed the carburetor in an attempt to make it a bit more economical to drive, and the side effect of the smaller Holley is that it is also a little more civilized. He didn't know much about it and told me that he believes it was originally an L88 but that he thought it had some later 427 in it now. Well, I know they didn't build L88s in 1966, so I looked at the numbers. Lo and behold, it most certainly appears to be a matching-numbers L72 427/425. Chevy actually rated this engine at 450 horsepower, but early in the year changed it to 425 without changing any of the hardware, so it was just GM playing their number games. 


I also believe that the 39,057 miles showing on the odometer is a correct reading and that the car probably spent some part of its life on the drag strip. There are signs that the engine has been rebuilt at some point, there's an explosion-proof bell housing, and a Muncie 4-speed from a 1968 Corvette, plus a set of ancient air shocks out back. It has also been repainted at some point, changed from its original code 972 Ermine White to a kind of mossy green that I'm calling Goodwood Green but it's not quite that one, either. Someone did a fine job of it, however, because I can find no trace of white anywhere on the car and even though I suspect it was done in the '80s, it's holding up extremely well. An aggressive professional buff would probably make it 95%. No cracks in the usual spots, gaps are excellent, and there's no sign of damage or botched-up work. The doors close better than any Mid-Year 'Vette I've ever had. If I have a complaint, the headlights are a little lazy.


The code 420 tan vinyl interior appears to be original and it's nice. No splits or tears, no scuffs, and aside from being a little shiny, the seats are ready to go--more proof that the mileage is legit. All the gauges work, including the 6500 RPM redline tach that was unique to the solid-lifter L72, and even the clock ticks away. Options include power windows, power antenna, a telescoping steering column, and the wood steering wheel with just perfect patina. There's a newer radio and speakers in the cargo bay, but the original AM/FM radio is included and those speakers are easy to remove.


All the numbers line up correctly to suggest this is the car's original, numbers-matching engine. It's a 3904351 casting, it has an IP suffix code which is correct for a 425 horsepower engine with a manual transmission, and there’s a matching partial VIN. There are indications that it has been rebuilt at some point and it runs like a million bucks. Easy starts, nice idle, and holy hell is this sucker quick! It's detailed with Chevy Orange paint, chrome valve covers (which I believe should be painted), and an aftermarket air cleaner, although the original air cleaner and a giant 750 Holley double pumper are included. All the original ignition shielding is intact, including the plug wires, which is pretty rare. The transmission is a non-original but correct Muncie M21 feeding the original rear end which feels like it has pretty mild gears inside, maybe 3.36s. The side pipes sound heroic and the undercarriage is unrestored but in great shape with no issues or needs. those are real knock-offs, and they carry 215/75/15 Michelin radials, but I think this car would look killer with a fresh set of redlines.


I wasn't prepared to like this car as much as I do, but it's one of those cars with an interesting story that under-promises and over delivers. $89,900 and it's a big block 'Vette you can drive instead of hiding it in your garage and parking it on fairways. Cool car. Thanks for looking!


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Edited by Matt Harwood (see edit history)
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Hi Matt,

                    This is an interesting car and it's always fun to find a lost Corvette from just about any era, especially a big block 4 speed car. I have owned 50+ Corvettes and believe there are no bad ones, some are just better than others :lol:.

It's a shame so many put so much importance on the whole "numbers match" thing, almost disproportionately with Corvettes. I have sold a few of mine over the years and had the buyer ask me "Is it numbers matching?" and I'll respond Yes or No depending on the car. Then they ask me "Can you tell me what that means?" They don't understand it, but they think it's important. I usually tell them "Look, at 60 miles an hour down the highway, it's a great car and nobody can see if the numbers match or not".

That being said, I think it's pretty safe to say that this is not the original engine for this car. Here are a couple of quick ways to tell:

The 3904351 block casting was not used until 1967. The 1966 cars used the 3869942 and the 3855961, and while it can be argued that a very late '66 might have used the '351 block this particular car is an April build, where production continued until July. The cast date code on the block will probably confirm this for you.

The stamp appears to have been done with individual stamps rather than with a proper gang holder. The re-stamp has used the number "1" where GM used the letter "I" (see pic for comparison) and the stamp date shown is April 11 where the VIN build date is April 2, which is backwards.

Still a very cool car for someone to restore, I'd like to have it myself. I actually like the non-factory color too.

Good Luck, Greg




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Thanks for the additional information, Greg. This is always a slightly murky area on these cars and I do the best I can with the tools available. I try to get it right because this kind of thing has gotten ridiculously over-blown in terms of how important it is to a car's value. In this case, my Corvette Black Book says the casting is correct for late production 1966. How late is late? I don't know, but April seems late if July was the model year change-over. 




I have not found the casting date, which requires removing the starter. It is not up top so it's a pre-1969 block at the very least.


The numbers on the stamping pad set off my detector a little bit, but the numbers are the right ones. The car's build date (H23) is April 23, while the engine's assembly date appears to be April 11. Maybe a little close, but not totally unreasonable. The one thing that that I have been told by several experts who have been hired to vet cars in our showroom is that nobody can ever be 100% certain of anything or exactly how the factory did something on a given day. That seems like an excuse or a cop-out, but one of those experts who said that was vetting this very original 1966 Impala SS427 convertible that I pulled out of a barn in Pennsylvania a few years ago--a car I really wanted to keep for myself. It was a one-owner car with 28,000 original miles that had never been apart--it still had the cable attached to the left side exhaust manifold to keep the engine from torquing over and damaging the wiring--a recall instructed dealers to install the cable on certain cars built before the engine mounts were redesigned. That expert saw this stamping pad and said he'd never seen a font like that, but that he had no choice but to pronounce it legit given all the other evidence (including a build sheet). I sold the car to a guy who wanted it more than I did, and he has won every major award a survivor like that can earn. Here's the car and its engine stamp:


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And now that I'm looking through my photos of that Imp (man, I miss it), I note that it also carried a 3904351 casting (blurry one is the Impala--sorry--clear one is the Corvette) even though it was a 390 horsepower hydraulic lifter car with an automatic transmission. There was no question that was a correct, matching-numbers car in every way.


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As for the numbers on the stamping pad, here's a 1964 Impala engine stamp that shows the same unusual "1" instead of an "I":




And a slightly later Corvette stamping that also uses the same "1":




This is the pad from a car that was represented as "100% matching numbers" by a big auction house. This one set off my BS detector and a buyer paid us to remove the starter and confirm (I did not advertise this car as "matching numbers" because it didn't look right, but he was hoping I was wrong):




I also don't see any broach marks on the Corvette's stamping pad that would indicate the block has been decked and the original numbers wiped out. You could dress those out of sight, but if someone was being that careful with their fraud, why be sloppy with the stamping part?


Finally, I have to wonder if anyone was really faking these things back in the '80s. This particular Corvette was found abandoned in a house being torn down by the city. I don't know when the engine was rebuilt, but it was surely before it was unearthed in the early '90s. Was anyone faking engine stamping numbers in, say, 1987? I doubt it because "matching numbers" wasn't even a thing until the mid-90s. The timing and the car's disposition don't lend themselves to the idea of a fraudulent presentation. The old guy from whom I got the car was totally clueless, so I doubt he's one to perpetrate fraud--heck, he thought it was an L88.


What does any of this prove? Nothing beyond the fact that GM was in the business of building production cars, not collector cars. If it was a question of using the wrong part and letting One-Eyed Bill stamp the numbers or stopping the line, well, they used the wrong parts and let One-Eyed Bill stamp the numbers. Today's obsession with matching numbers is the stupidest thing in the world and I'm constantly frustrated by this kind of esoterica. What's worse, it has spread to every corner of the hobby and is corroding it from within with people who think old cars are "investments." Model A guys ask about "matching numbers." Guys buying $7000 Nash Metropolitans ask about "numbers matching" and "protecting my investment." Mercedes and Jaguar buyers have gotten exceptionally obsessed with numbers to the point where I don't even want to deal with the cars anymore because the buyers are lunatics about numbers. My only recourse is to do as much homework as I can, but there's a reason why every one of my ads regarding a "matching numbers" car has the disclaimer that you should hire your own expert to examine the car. I'm just one guy with a certain set of skills--I need to know a little about everything, but I can't be an expert in all things. There are plenty of people who know more than I do (and they frequently and gleefully rub it in my face), so if you have concerns, hire one of them to do your homework for you. If you don't want to do that, then that's on you.


I really do try to get this stuff right and I spend more time than I should studying it rather than let the buyer make up his own mind. Maybe that's a mistake, but if I don't vet it, I will get 600 phone calls from guys asking, "Is it matching numbers?"


In fact, I don't know if any of you have noticed this, but few, if any, of the auction companies will even mention "matching numbers" in their printed descriptions anymore, no matter what the car. What's worse, I'm reading magazines with auction results in them and I note that THOSE authors won't mention anything about matching-numbers, either, even after the car has sold. These are the very same assholes who created this matching-numbers monster in the first place and now they're distancing themselves from it because it has gotten so out of control and they are getting sued over it. Screw that and screw them.


Matching numbers is idiotic. There, I said it. I'd much rather have a non-matching car that I can drive the hell out of without worries than some car with a slightly different set of numbers that makes me terrified to destroy my "investment." That's just moronic.


I've presented the relevant information on this particular Corvette. If you're seriously interested in the car, please come see it with your expert. I will let you spend all the time you need, we'll put it on the lift, and you can poke and prod to ensure that it is what you expect.


I can't do more than that.



Edited by Matt Harwood (see edit history)
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"The car's build date (H23) is April 23" 

The body tag you show is an A.O. Smith tag rather than a St. Louis built body so the build date is actually March 23 rather than April 23. The engine is a later stamp than the car, which just could not be.

Very interesting Impala and certainly a rare bird by any standard. It is a little difficult to read the first stamped number in the pic you've posted for the Impala so I cannot read the date or tell if it's a Tonawanda block or a Flint block but it certainly could be the correct engine for this 1966 Impala (as the judges have proven) if the car is a very late build. Other 1966 models have appeared with the '351 block but they were built in the last few weeks of production rather than months.

The unusual looking font used for the sequence code on that car is actually not that unusual. While Chevrolet dictated the VIN stamping procedure and all '65 through '69 characters were supposed to be 3/16" high, the choice of font/style of the stamps was made by each final assembly plant....and there were 12 of them.

The exception to this rather loose rule of thumb was the Corvette. Due to the fact that they were only assembled in one plant the stamping procedure is very well documented and the fonts remained the same. Letters were 5/32" high until the body style change in 1968 when they moved to 1/8" letters. So there would be no correlation between a different Chevrolet platform, built elsewhere using various fonts and the fonts/stamps used on Corvettes.

I am in complete agreement with you on the over-importance levied on the whole "numbers match" thing today. Especially on Corvettes (I think Ferrari guys are worse). I am in the camp of "who cares?" If you like the car, drive it. This is a never ending issue on one of the Corvette boards I've been with for 20 years. It never seems to go away.

Again, no harm intended. I am pretty well versed in Corvettes of this era so I'm just passing this info along for your benefit if you can use it.

Cheers, Greg

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14 hours ago, GregLaR said:

The engine is a later stamp than the car, which just could not be

Not to be augmentive but this statement isnt correct in all cases.  I recently sold a 1961 Pontiac Ventura,  a 425A / 4 speed car, a fairly rare car. The build date on the cowl tag was 4th week of Nov. 1960, the engine was dated Dec 20, 1960. The Pontiac Historical Service documented the car for me and supplied me with the build sheet, hand written on this document was " body placed in asle 4". PHS explained to me that this indecated the assembly plant had not received the motor when the car came down the assembly line so it was placed in storage until the motor was received.  They also said this was a fairly common occurrence with cars that were ordered with unusual equipment.  Fortunately for Pontiac fans the records are available starting with 1961, unfortunately Chevrolet records are non existent,  however if these occurrences happened at Pontiac they undoubtedly also happened at Chevrolet. Not saying this was the case with this Corvette but a 425 horse 427 Corvette would be a perfect example of it may have happened .

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Looks like I have another car to kick out of my shop. At least I've invested a few thousand bucks in cleaning it up, servicing it, and advertising it, which is nice. 


I'll keep this thread in place in case it's useful to anyone else in the future, but I am now inclined to agree with Greg that it's bogus. There's gray area, but it isn't wide enough to hide the build date and the engine assembly date not jibing, Tommy's evidence notwithstanding. I didn't know about the AO Smith tag/build date difference, and the chart I used to check date codes was badly formatted to obscure the difference. Once I double-checked, I was able to confirm what he said. Combined with the somewhat hinky-looking stampings, I can't imagine any serious Corvette buyer wanting to buy this thing now. 


Easy come, easy go. 

Edited by Matt Harwood (see edit history)
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The only numbers matching Chevrolet I ever owned that I paid any attention to was an interesting one.

A 1966 Impala four door hard top with a 427 and a three on the tree.

I got it from the old guy that ordered it new. (He also had a matching ElCamino that he bought at the same time but was a 283 Automatic).

I had to bore the 427 because of a wrist pin damaging one of the cylinders. So a std crank/ 030 over bore.

The body was very straight but faded so I had it painted in its original color which was a dark green.

Some (**&^%$s stole it right off my lot.

I have the title that has the vin on it and I clearly remember it was similar to the number stamped on the block.

This was in the eighties, and I am still pissed. The cops in my town don't like me much and made no effort to solve the crime.

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  • 2 weeks later...

The problem with all this numbers matching stuff is that guys with deep pockets will pay up for these cars even though most are certainly faked! The price difference is too great on a numbers matching car and a non original engine car. I think that as long as a car had a 427 engine from new and has the engine replaced that should have some merit! I myself would love to have a 67 vette with the 427 and I really would not care to much if it had the wrong engine as long as the price was in line with the car! Fred

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