Need help with engine identification

[phlfly]

Hello,

Bought 1991 W126 350 SDL. Previous owner has told me is an engine was change 3 years ago with 120,000 replacement. But when I asked whats is donor car , he doesn't remember.
So my question how to know if 603.961 or 603.97x?

Thanks

[Diseasel300]

The block should have a casting number on it. There will be a string of numbers with the engine number in it. You'll be a 603960, 603961, 603970, or 603971 in the number string depending on which car it came out of.

[Diseasel300]

Someone else recently asked a similar question in another thread.

W140 300sd block #

[phlfly]

thanks guy I will report back tomorrow it's too dark now

[phlfly]

it's 961. So it's good or bad ?

[Diseasel300]

961 is out of a 300SDL. Block is strong on them. Check the head casting to determine how good your engine is. #14 head is weak, but can be reliable if the engine is maintained and never allowed to overheat. #17 or later is desirable for long term durability. I wouldn't get too hung up on the head issue, I'm running the original #14 on mine, and several others here still have their original #14 with way more miles than I do. More info on how to tell here: 1986 w124 300d cylinder head cast number

[phlfly]

Originally Posted by Diseasel300

961 is out of a 300SDL. Block is strong on them. Check the head casting to determine how good your engine is. #14 head is weak, but can be reliable if the engine is maintained and never allowed to overheat. #17 or later is desirable for long term durability. I wouldn't get too hung up on the head issue, I'm running the original #14 on mine, and several others here still have their original #14 with way more miles than I do. More info on how to tell here: 1986 w124 300d cylinder head cast number

It's #14. Temp gauge sits always around 80.

[phlfly]

This is few picture of SDL: