1972 LT-1 numbers questions

[Mike E.]

Re: 1972 LT-1 numbers questions

It strikes me that the "L" in the vin tag is unusually tall in relationship to the other digits. Also, on the pad stamping on the block, it's hard to tell with the paint on it, but the vin derivative stamping looks correct, but shallow. The assembly code is stamped with individual stamps rather than gang stamped.
So, IF the car was originally an LT-1, I believe the stamp pad has been altered to make it appear it was originally an ac car. My best bet is that it was not an LT-1 originally, but still has the original base-motor engine.

[Joe R.]

Re: 1972 LT-1 numbers questions

Mike,

Read carefully the above post by Patrick Boyd. It's a great read and explains this LT-1 completely.

JR

PS. Patrick should write the complete book of engine stamps. It hasn't been written yet!

[Michael W.]

Re: 1972 LT-1 numbers questions

CKY would be LT1, with or without A/C.

CKW would be base engine.

Are we saying that the VIN tag has been altered to change a base engine tag which would have 'K' into an LT1 car with an 'L'?

[Patrick H.]

Re: 1972 LT-1 numbers questions

The VIN plate on the windshield pillar should be black, so I'm not sure why the seller scraped it off. Now it just looks really bad. However, the black paint that is on it appears thicker and has more gloss than typical factory appearance. I would also agree that the L character in the VIN appears taller than typical.

In addition, he appears to have scraped the engine stamp pad to remove the paint, which only added more scratches to what was already on there.

[Joe L.]

Re: 1972 LT-1 numbers questions

All------


The car does have an LT-1 harmonic balancer, so if it's an original base engine, the balancer has been changed.

The car does have 2-1/2" exhaust and the pipes appear original (or, original GM replacements). Base engine would have had 2" exhaust.

The carburetor is not original or it's been modified.

Cylinder heads are not 1972. Casting symbol is 1970 or earlier.

Does the car have an original windshield? If so, it's unlikely the VIN tag has been changed. VERY difficult, if not impossible, to change a 68+ VIN tag without removing the windshield (and, likely breaking it on removal).

[Christian R.]

Re: 1972 LT-1 numbers questions

At Joe : Are you sure the cylinder heads are not the correct one for 1972 LT-1 engine ? The numbers are identical to normal engine this year : correct ?
My thoughts are : the car is a genuine LT-1 with A/C, but it's original engine was broken at the early of it's life. In this time, some people had changed the engine with another (maybe also a LT-1...or not ?). They eventually took some parts on the old (maybe the harmonic balancer, fuel pump,...) and grounded/re-stamped the engine by hand with right numbers for the car.
But I'm really not an expert and mybe I'm totally wrong ? The only, for me, right way to be sure is to remove the oil pan to check the 4-mains bolt... But the seller won't do that, I'm quite sure...

[Sal C.]

Re: 1972 LT-1 numbers questions

I have photos or tracings of 11 CKY pads on file. 6 of them have individually stamped suffixes. Have seen more, pretty normal.

[Michael W.]

Re: 1972 LT-1 numbers questions

The only, for me, right way to be sure is to remove the oil pan to check the 4-mains bolt... But the seller won't do that, I'm quite sure...

Four bolts mains are not unique to LT1 engines and any Flint 0010 engine case can be modified to accept them.

[Sal C.]

Re: 1972 LT-1 numbers questions

I have photos or tracings of 11 CKY pads on file. 6 of them have individually stamped suffixes. Have seen more, pretty normal.

[Patrick B.]

Re: 1972 LT-1 numbers questions

Sal -- Are any of them jpg images that you could post for us?

[Sal C.]

Re: 1972 LT-1 numbers questions

[Christian R.]

Re: 1972 LT-1 numbers questions

Thank you for these pictures !
Do you think that was possible the surface of the stamping was milled down to clear the original markings and restamped ?
We can see on my stamp pictures an offset between Deck block surface and cylinder head : the surface of the pad is much lower than the level of the head gasket surface...

[Joe L.]

Re: 1972 LT-1 numbers questions

At Joe : Are you sure the cylinder heads are not the correct one for 1972 LT-1 engine ? The numbers are identical to normal engine this year : correct ?
My thoughts are : the car is a genuine LT-1 with A/C, but it's original engine was broken at the early of it's life. In this time, some people had changed the engine with another (maybe also a LT-1...or not ?). They eventually took some parts on the old (maybe the harmonic balancer, fuel pump,...) and grounded/re-stamped the engine by hand with right numbers for the car.
But I'm really not an expert and mybe I'm totally wrong ? The only, for me, right way to be sure is to remove the oil pan to check the 4-mains bolt... But the seller won't do that, I'm quite sure...

Christian------

The cylinder head casting symbol I see in your photo of the pad (i.e "double hump") was not used for 1972 for any engine. The style casting symbol seen in your photo was used for 1969-70 only. So, I expect your heads are either 3927186, 3927187, or 3973414. None of these heads were used for 1972. You can verify simply by removing a valve cover.

And, yes, either the base engine for 1972 or the LT-1 used the same cylinder head casting. The finish machining of the heads was the difference.

By the way, what is the block casting number and casting date? These can be seen on the bellhousing flange without removing anything.

[Joe L.]

Re: 1972 LT-1 numbers questions

Thank you for these pictures !
Do you think that was possible the surface of the stamping was milled down to clear the original markings and restamped ?
We can see on my stamp pictures an offset between Deck block surface and cylinder head : the surface of the pad is much lower than the level of the head gasket surface...

Christian------


Are you saying that there is a step between the block's deck surface and the surface of the engine pad? Keep in mind that there is a slight "recess" on the bottom of the front edge of the cylinder head in the area of the pad that might make it appear to be a step. You can see this "recess" clearly in Sal's first photo of an engine pad.

[Joe L.]

Re: 1972 LT-1 numbers questions

I have photos or tracings of 11 CKY pads on file. 6 of them have individually stamped suffixes. Have seen more, pretty normal.

Sal------

While I have not made any study of this myself, I'm not surprised, at all, by what you mention. In fact, I kind of thought that the offset suffix code characters might be original when I first saw the OP's photos of the pad. One reason is that the VIN derivative appears legit and I can not understand how a VIN derivative could be legit and an engine code illegitimate. Here's what I think happened at Flint:

The assembly line station at which the engine stamping took place had a rack of gang stamps, each set up each day with the date and suffix codes for all of the engines being manufactured on that line. However, LT-1 engines were a relatively small volume of engines produced. So, on some days the line person may not have wanted to set up a gang stamp for LT-1's (or, they had an insufficient number of gang stamp holders for all of the engines). One of the gang stamps might have been set up as "generic" (i.e. including only the "C" which all engine codes began with) but no successive characters. So, they decided to individually hand stamp 2 (or 3) of the characters for the suffix code when an LT-1 engine came along.