Number and letter stampings in the Mains area 1972 454 LS-5

[Owen L.]

In sleuthing my non-correct oil pan, and making sure my block is what I thought it was (as in original to the car, correct castings, correct dates, etc) I came across hand-stamped letters and numbers near the oil pan rail:


IMG_2512.jpeg IMG_2513.jpeg IMG_2514.jpeg IMG_2517.jpg
Above each cylinder's cavity you can see either an "8" or a "9" (upside down in the pic) stamped into the block. The last pic shows several "B" stampings. All but two cylinders have these number stampings and other than the one cylinder no others have any letters. Upon disassembly, the block had all of its original bearings, pistons, and has never been bored.

Any clue what these stampings may indicate?

[Joe L.]

Re: Number and letter stampings in the Mains area 1972 454 LS-5

In sleuthing my non-correct oil pan, and making sure my block is what I thought it was (as in original to the car, correct castings, correct dates, etc) I came across hand-stamped letters and numbers near the oil pan rail:


[ATTACH=CONFIG]97709[/ATTACH] [ATTACH=CONFIG]97710[/ATTACH] [ATTACH=CONFIG]97711[/ATTACH] [ATTACH=CONFIG]97712[/ATTACH]
Above each cylinder's cavity you can see either an "8" or a "9" (upside down in the pic) stamped into the block. The last pic shows several "B" stampings. All but two cylinders have these number stampings and other than the one cylinder no others have any letters. Upon disassembly, the block had all of its original bearings, pistons, and has never been bored.

Any clue what these stampings may indicate?

Owen------


These stampings are often seen on factory short blocks. I believe they are somehow related to the piston to be installed in each bore. I do not know what the "B" denotes.

[Terry M.]

Re: Number and letter stampings in the Mains area 1972 454 LS-5

In sleuthing my non-correct oil pan, and making sure my block is what I thought it was (as in original to the car, correct castings, correct dates, etc) I came across hand-stamped letters and numbers near the oil pan rail:


[ATTACH=CONFIG]97709[/ATTACH] [ATTACH=CONFIG]97710[/ATTACH] [ATTACH=CONFIG]97711[/ATTACH] [ATTACH=CONFIG]97712[/ATTACH]
Above each cylinder's cavity you can see either an "8" or a "9" (upside down in the pic) stamped into the block. The last pic shows several "B" stampings. All but two cylinders have these number stampings and other than the one cylinder no others have any letters. Upon disassembly, the block had all of its original bearings, pistons, and has never been bored.

Any clue what these stampings may indicate?

These stamps relate to the cylinder bore size and thus trigger certain piston sizes. What they specifically mean would remain with some engine assembly plant workers.

[Owen L.]

Re: Number and letter stampings in the Mains area 1972 454 LS-5

Thank you Joe and Terry.
(The pistons matching these cylinder bores don't carry any similar stampings.) And that guy with the B stamp really went wild with it and had a hard time not placing it right on or near the edge of the pan surface!

I guess I'll just chalk it up to "one of those mysteries" for the moment.

Owen

[Terry M.]

Re: Number and letter stampings in the Mains area 1972 454 LS-5

Thank you Joe and Terry.
(The pistons matching these cylinder bores don't carry any similar stampings.) And that guy with the B stamp really went wild with it and had a hard time not placing it right on or near the edge of the pan surface!

I guess I'll just chalk it up to "one of those mysteries" for the moment.

Owen

I am not sure if or where the pistons were marked, but I suspect they must have been somehow marked because they were selectively sized and fitted to the bores. The bearings were selectively fitted to the crankshaft as well. If your engine has the original bearings the back side will be stamped with numbers indicating the size. I have also seen a date stamped on the back side of the original bearings.

Now days machining is so precise that each bore is exactly (well almost) the same size and each piston is almost exactly the same size as well. Thus any piston will fit in any bore, so there is no more selective fitting.

[Ray K.]

Re: Number and letter stampings in the Mains area 1972 454 LS-5

The number stamping by each cylinder bore do indeed refer to the piston selection to match the bore size. Sometimes the number is prefixed with the letter " S ". Here are examples from the charts that I have.

350 cu in engine
4.0000 - Std, 4.0010 - .001, S4 - 4.0000 to 4.0005, S5 - 4.0005 to 4.0010, S6 - 4.0010 to 4.0015, S7 - 4.0015 to 4.0020

427 cu in engine
4.2488 - Std, 4.2498 - .001, S4 - 4.2488 to 4.2493, S5 - 4.2493 to 4.2498, S6 - 4.2498 to 4.2503, S7 - 4.2503 to 4.2508

I do not have a chart for the 454 engine, but you can see how the sequence goes. I think the B stamping may be for the individual or the shift.

Ray

[Owen L.]

Re: Number and letter stampings in the Mains area 1972 454 LS-5

The number stamping by each cylinder bore do indeed refer to the piston selection to match the bore size.
<snip>
427 cu in engine
4.2488 - Std, 4.2498 - .001, S4 - 4.2488 to 4.2493, S5 - 4.2493 to 4.2498, S6 - 4.2498 to 4.2503, S7 - 4.2503 to 4.2508

I do not have a chart for the 454 engine, but you can see how the sequence goes. I think the B stamping may be for the individual or the shift.
Ray

Thanks Ray. I examined every piston with its connecting rod this afternoon and I can't see any markings whatsoever that would indicate a difference between them. Not saying its not true, I just can't find it. Maybe the components themselves aren't marked and were just pulled from appropriately marked bins.

That "B" guy went nuts as there are probably 5 or 6 impressions around the 6 and 8 cavities -- maybe it was the first engine Monday morning and he had a very rough weekend!

After writing the above, I went to look at the Flint engine assembly book by John Hinckley (http://www.camaros.org/pdf/flint_engine.pdf) I assume Tonowanda followed a similar process as outlined from Flint.

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