72 LT1- Engine Block / Cylinder Head Date Questions

[David S.]

Can someone explain this to me. I have a cylinder head that is P/N 3973487X and dated N 8 2. I know the part number is for a 72 LT1, but I have never seen or heard of a date code beginning with an N for the month.

Also the block is a 3970010 casting number but the date casting appears to be "LW"? What date is LW? I think the block is a service replacement, would that make the difference?

Any clarification is appreciated.

Dave

[Joe L.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

Can someone explain this to me. I have a cylinder head that is P/N 3973487X and dated N 8 2. I know the part number is for a 72 LT1, but I have never seen or heard of a date code beginning with an N for the month.

Also the block is a 3970010 casting number but the date casting appears to be "LW"? What date is LW? I think the block is a service replacement, would that make the difference?

Any clarification is appreciated.

Dave

Dave------


I've never heard of or seen an "N" code used to denote month in a casting date. Given that there are only 12 months in the year, "L" is as high as it can get. Even if they were to not use an "I" (and they almost always did use an "I" for casting dates), they would only get to "M". Casting dates and numbers can be notoriously difficult to discern at times. I suspect it's actually some character other than an "N". Otherwise, the only way I can see it happening is by foundry error. That's possible, of course.

"LW" would not represent a casting date on the block. SERVICE blocks were dated exactly the same as PRODUCTION blocks during the entire period that the 3970010 block was being produced (1969-1979). So, I do not know what the "LW" represents.

[David S.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

Hi Joe,

As always thanks for the quick response. I've posted some pictures.... I'll try to get a better one of the block casting date. Now that I'm seeing it in a different angle it appears to be L 17. I still think its missing a year code.

[Joe L.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

Hi Joe,

As always thanks for the quick response. I've posted some pictures.... I'll try to get a better one of the block casting date. Now that I'm seeing it in a different angle it appears to be L 17. I still think its missing a year code.

Dave------


Well, I'd say it's definitely an "N" for the month code on the head. So, I'd say it has to be some sort of foundry error. However, I suppose it's possible it was somehow connected to the late model year introduction of the "X" suffix heads. How the "N" decodes I have no idea. Maybe Mark Gorney could advise.

The block casting date does look strange but I think it probably is "L 1 7", although I think someone used an "upside down 7" for the "L" character. So, the date would be December 1, 1977 (1977 was the only year with a last digit of "7" during the period the 3970010 block was produced). What is found on the stamp pad of this engine?

[David S.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

This LT1 is a very late car. (June 1972). The 70-72 Technical Manual states "X indicates that an X-Casting foundry proof-mark appears after the seven-digit casting number on later 1972 3973487 base and LT1 cylinder heads." I think the head is correct for the car but clearly the plant made a mistake casting the head? The other head is dated C 8 2 (March 8, 1972).

The stamp pad is blank. The car spun a bearing in 1972 and was brought back to the dealer for a replacement engine. Its a short stamp pad engine. I was told the engine swap was done in 1973.

Thanks,
Dave

[Edward J.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

David, maybe a suffix stamp from engine may help shed some light, with the LW stamp. Do you believe the engine is the factory original?

[Terry M.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

This LT1 is a very late car. (June 1972). The 70-72 Technical Manual states "X indicates that an X-Casting foundry proof-mark appears after the seven-digit casting number on later 1972 3973487 base and LT1 cylinder heads." I think the head is correct for the car but clearly the plant made a mistake casting the head? The other head is dated C 8 2 (March 8, 1972).

The stamp pad is blank. The car spun a bearing in 1972 and was brought back to the dealer for a replacement engine. Its a short stamp pad engine. I was told the engine swap was done in 1973.
Thanks,
Dave

By short stamp pad, do you mean the stamp pad is closer to square than rectangular? If so that would point toward the 1977 date. I believe by then the stamp pad was closer to square shape. 1974 is, I believe, too early for the almost square stamp pad. Those guys who judge later C3s, or someone with those Judging Manuals, would be able to advise better.

[Michael W.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

1974 is, I believe, too early for the almost square stamp pad.

That's correct Terry.

[David S.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

David, maybe a suffix stamp from engine may help shed some light, with the LW stamp. Do you believe the engine is the factory original?

The engine pad is blank. Its not the original block. It was replaced in the early - mid 70's (so I'm told), due to a spun bearing.

Thanks,
Dave

[David S.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

By short stamp pad, do you mean the stamp pad is closer to square than rectangular? If so that would point toward the 1977 date. I believe by then the stamp pad was closer to square shape. 1974 is, I believe, too early for the almost square stamp pad. Those guys who judge later C3s, or someone with those Judging Manuals, would be able to advise better.

That is correct. The engine pad is more square than rectangle.

[Michael W.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

That is correct. The engine pad is more square than rectangle.

That more less confirms that the casting date is 1977 vintage. The 3973487X heads were used on base engine '72s as well as LT-1, but the casting date is still a mystery.

[Terry M.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

There is a chance that the N on those heads serves the same function as the M we see on some cylinder cases. Mark Gorney might be able to enlighten us.

Of course I assUme y'all know what the M on the cylinder cases mean after two stories in The Corvette Restorer.

[Joe L.]

Re: 72 LT1- Engine Block / Cylinder Head Date Questions

This LT1 is a very late car. (June 1972). The 70-72 Technical Manual states "X indicates that an X-Casting foundry proof-mark appears after the seven-digit casting number on later 1972 3973487 base and LT1 cylinder heads." I think the head is correct for the car but clearly the plant made a mistake casting the head? The other head is dated C 8 2 (March 8, 1972).

The stamp pad is blank. The car spun a bearing in 1972 and was brought back to the dealer for a replacement engine. Its a short stamp pad engine. I was told the engine swap was done in 1973.

Thanks,
Dave

Dave-----


The blank stamp pad indicates the block was originally supplied in SERVICE as either a bare block, fitted block, or partial engine ("short block"). The stamp pad configuration definitely indicates a later block and, most likely, the 1977 date seen on the casting.

The heads are most likely original to the car, notwithstanding the "N" casting date error. So, what happened was very likely about what you've been told: there was some sort of failure involving the need to replace the block but not involving a need to replace the heads. So, the heads were transferred to the replacement block.

The part of the story that I doubt is that this replacement occurred in the early 70's. No way did it occur in the 72-74 period. However, what does it matter? It's a replacement block and it's just about equally incorrect whether it was replaced in 1972 or 1977, albeit a 1972 replacement would have a more correct stamp pad configuration..