1975 911 Engine serial number and engine type inconsistency

[heymj73]

Hopefully someone may be able to provide some context or confirm my thoughts on the matter.
I have a 1975 911. The VIN decodes to a 1975 911 S Carrera US (9115400138).
I'm confused with the engine number/engine case type.
The serial number on the engine is 6457014 - which from my cross referencing matches the VIN, i.e. a 911s/c US engine. This engine should have a 911/43 case.
However my engine case is 911/98 (the photo is a bit rough, in real life it the stamping is more clear), which cross references to a 1974 sportomatic.
The car has a 915 trans.
Any thoughts?
Did Porsche mix and match with parts (like the italians), and the reference tables need to be read with a grain of salt?
Or could it be a replacement motor, where someone has gone to the trouble of machining out the original serial number and restamping it?
Thanks

[dannobee]

Case was replaced. "New" case was restamped. The original engine serial numbers have a star stamped at each end of the serial number.

[Evan Fullerton]

All sorts of strange things have happened with unserialized replacement cases. I have a 3.2L case with 1976 Carrera 3.0 Type 930/02 and 666XXX case numbers.

[heymj73]

Thanks both - makes sense

[djpateman]

The "new" case was an old case where the original serial was removed (but they did not remove the original type #). As stated, the new serial # does not have the stars.
Someone did a poor job of faking an engine #.

[Matt Monson]

Originally Posted by djpateman

The "new" case was an old case where the original serial was removed (but they did not remove the original type #). As stated, the new serial # does not have the stars.
Someone did a poor job of faking an engine #.

All the new replacement cases I have seen over the years had a type number but not a serial number. We had a number of them that we got from Vasek and Carl Thompson back when I worked at Carquip.

This particular one looks like it was stamped by a shop, and not by Porsche.

[RobFrost]

There's nothing fake about a replacement case. It's the engine number, not the case number so perfectly legit in my view to transfer the correct engine number over to the replacement case.

Sent from my SM-G988B using Tapatalk

[group911@aol.co]

The case in the picture appears to have been altered prior to stamping.

[356RS]

Originally Posted by group911@aol.co

The case in the picture appears to have been altered prior to stamping.

Yes it looks like it was ground down and then smooth over then stamped.

[Matt Monson]

Now that I'm at a computer, I can see just how bad that is!!! You'd think if they were going to grind it, they would at least keep the edge square. Someone really had their way with that.

[2bewild]

Hello everyone, I am a relative rookie to the forum.

Is this the correct place to post a question about the cross-reference for my engine SN?

I have a used 911 engine in my possession, and the SN is stamped: *6282493*.
Can anyone tell me what car it came out of, and what the engine case number should be?

I just want to trace it's lineage for my records, and for when I need to look up parts.

The local Porsche dealership knows absolutely NOTHING about engine SN and cross-referencing to the model/year (and, based on their ebody language in a recent email exchange, I don't think they want to know...).

Many thanks.

[targa72e]

Try this site.
https://www.stuttcars.com/porsche-911-engine-numbers-1965-1989/

Type number helpful in determining what you have. You will notice that the serial numbers loop which is where the type number is important. For example 619 XXXX could be a 79 SC engine or a 69 T engine.

John