Decked block

[dale_z28]

I'm fairly new to the site but I hope you'll pardon me if this isn't the right place for my question: I had my 302-DZ block B&B'd back in the early '80's, and when the block was decked I lost my numbers. Now that the Z28's are much more collectible and everyone's grandmother knows to look for the "DZ" below the alternator, I'm trying to find a way to "obtain" my numbers? Isn't it a combination of the VIN, the date of casting or manufacture (the block) and the displacement (the 302=DZ)?

I won't try to restamp the block, I believe that would throw up red flags and make it suspect of a forgery, I'd really just like to have the information. I heard of an acid procedure used by police for recovering ground-off numbers, and  I was lucky enough to speak with a state police  post commander who looked up my VIN and told me where my car was delivered, and some other info... but he said the acid method isn't reliable enough and they hardly use it.

So, anyone know if my numbers can be created by the casting numbers and other parts? I am certain mine is a numbers-matching '69, I'm just missing the second-most important stampings to prove it. 

[BULLITT65]

Well the easiest way to figure out what your original block stamping would be is if you have the protecto-plate, (metal credit card in the Owners service manual). It will have all the pertinent info on it. If like many Owners you do not have it, depending on when your car was built you may have the vin stamped by the oil filter, but it is hard to see. The casting and internal parts could identify it as a 302, but won't tell you what the DZ stamp would have been. Those casting numbers along with data from other cars built close to yours could make for a educated guess only.

[dale_z28]

Thanks, Bullitt. No, I don't have the Protecto-plate. I have looked (but will look again to be sure) around the oil filter area, but if there is a number, will it be the VIN, which would tie it to the car? I do have the casting numbers/date codes to show it is of the correct period, as are all the other numbers on the car. I was just hoping somehow they all could be combined so that I would have the complete engine code. Who knows, I may have written it down in my old Chiltons manual.

I have the original window sticker, and was told there are Chevrolet folks who do historical research to provide some documentation of authenticity. Can Protecto-plates be reproduced using information gathered this way?

Mine is a Norwood car, and like me, born in February. I may never know the engine code. I had no idea when I bought the car in 1977 how important that number was!

Thanks again for the response, Bullitt!

[69Z28-RS]

Without the original deck stamping or the Protecto-plate there is NO way to know the actual application stamping that would have been put on in the Flint plant when the engine was assembled.   Assuming it is the original 'DZ' engine, then the 'form' is VwxyzDZ, where the wxyz is the date the engine was assembled.  Besides knowing it would follow the date of the block and head casting numbers, there is no way to know what this date would have been besides the two possibilities pointed out.

Assuming your car does have the factory installed original motor (with stamped codes machined away), the best way to know that the engine is original to the car is if you can find/ID the VIN as stamped on the rough cast surface of the block by the Oil Filter boss.  If it is the original block (by VIN) then you could gain confidence the engine was an original DZ engine by clues from the casting/assembly other components in the engine (block cast code, heads, cam, crankshaft, rods, intake, distributor, alternator, etc).  IF All of these parts matched the original DZ specs with appropriate date codes, AND if no other aspect of your car indicated it was 'built up' into a Z28, then the evidence would point to your car being an original Z28.. (but would not be actual proof)...

[X33RS]

Actually, With a Norwood car that has a "real" data plate with an "X" code, you would know the car is a Z28 from the get go.

With that said, even if the DZ stamping has been decked, as long as the vin was stamped at the oil filter location, then all you would really need to know at this point is if the vin on the block matches the car.  That alone would be enough to prove it's a DZ motor.

If the vin was on the pad however and was removed along with the assembly date when decked, you're in a pickle.

[BULLITT65]

So if your february car has it stamped above the oil filter it will show 9NXXXXXX. (the X's would represent the last six of your vin number. Again very hard to see. try cleaning the area and then looking at it from different angles and different lighting.

Start a new thread with some pics of your car, recent and back from the 70's when you got it.

[dale_z28]

I saw the 'DZ-number' with my own eyes when I purchased it, as my auto shop teacher questioned it's originality. We researched it then, that's why I hope to run across it penciled-into my old Chilton manual. I don't need convincing, and I doubt that I'll ever sell the car; it's just a potential problem IF I do....
Thanks for the many replies, and I'll see what pictures I can come up with!

[X33RS]

It happens more often than one might think.  It's difficult to rebuild these engines and do them correctly, with everything "squared" up and not deck the block.   Now people are more conscious of numbers, but years ago no one cared.

It's not absolutely necessary to deck a block, but I've been running into quite a few with deck heights all messed up, taper from one end to the other off several thou', and I like tight quench on my engines.  Sometimes you can get there with piston pin compression height changes but to get it spot on the deck almost always needs a pass or two on it, especially when one end is higher than the other.  I just did a Windsor for a customer that was this way.  .007" taper front to back plus the OEM crank was short on it's advertised stroke (another common issue as they are never exact) Putting the piston further in the hole.   We had all kinds of goofy machine work to do on this one to make it right.  Luckily Ford doesn't put vins on the deck surface so no worries.   But this is another subject entirely, sorry to blab.

[dale_z28]

No prob, interesting stuff! Next time I'm "back home" (where my car is undergoing its resto) I'll look closely at the oil filter area.
One last thought, I have my original heads although one is cracked. I plan to save them as additional "evidence" if needed. Only thing I lack that makes it numbers-matching/complete are exhaust manifolds, which I would never put back on. I figure a light coat of "jam clear" should protect those heads. Anyone disagree?

[bcmiller]

This was a topic somewhat related but I split it off into its own thread.

[dale_z28]

Thanks, Bryon, forgive me if I'm posting in the wrong places or hijacking threads as I learn my way around. I really appreciate all the help, and I'll be putting up some pics soon. But first there's a leaky faucet on my honey-do list....

[bcmiller]

It's no problem Dale. And I am looking forward to the pics.

[dale_z28]

I posted some pics for practice if anyone is interested, in the "test" area...