That is one of the early Mega blocks hence the cast in M emblem in the middle of the block on both sides

Member “Zippy” knows a ton about these Mopar “mega” and “world” blocks. I think he worked in the industry when they were made and i remember him contributing to informing guys asking about them in the past. You could search this forum for those old posts with his input.

Thank you. And know I'm more confused than when I started. Mega good? Mega bad? World good world bad? Haha

They can be good or bad. You won't know until you take it all apart and have a pro check it out. Magnaflux, pressure check, sonic check, etc.

The casting date looks to me like it may be 2010. Just my guess

That's a full water jacket mega block. The siamese block has Mopar cast in it above the number.

Sorry, I really don't look on here as often as I probably should. Work and family, you know. But thank you for thinking about me.

I worked at MP as a Chrysler Contractor during the 2005 to 2013 era which allowed info to be collected. Some of it, I even still remember! (Kidding. Sort of)

MC foundry mark in a shield was Motor Castings. Cummins recon (everyone's favorite! kidding...) machined them for crate engine and bare block use at the end.
This was the pre-World block, usually known as Megablock,
even the water version which was noteably less "mega" than the siamese versions which were much more "mega".
Why?
Gearhead slang usually lumped siamese and water together as "mega"but as the I sheet shows, this was not accurate.
In Mopar Land the water block (non siamese) probably should have been sold more as a restoration block even though it had a few upgraded features like thicker
lifter bore bosses. The real megablock was siamese.

Engineering verbal parlance of the older parts referred to either a water block or siamese, to separate them.
megablock was a marketing term that was misused greatly by the public....kind of like "purple shaft".

In 2008 Chrysler sold off the last of the pre-world stuff as the new World Products ones came into pdc stock. For a short period of time, both versions
were sold....but the old ones were gone in a matter of months. I don't know what happened to to the tooling for the older versions but it's probably scrapped
if normal thought and foresight was applied. I don't think any older ones were cast or machined later than '08 but never say never/it's Mopar, unicorns and rainbows are the norm.


The new blocks were casting P5153843.
It was a big deal at the time, enough that I memorized the number.

"World" is a misnomer because World products did not actually cast or machine those.
Dalton Cast them and royal oak boring machined them.
I think World may have created the hardware kit, which many on Moparts said was trash because the main studs were no good.
World products were supposed to manage the entire block program, and they did such an amazing job that by 2014 or so, no more were being shipped.
I was no longer a chrysler contractor by then and was getting 3rd hand information which may be semi-accurate at best. (right here I've deleted a few negative sentences about Chrysler's idiotic decision to stick with the good-turned-horrible contract house as it's just a whiney vent, and not helpful).

My opinion-The block in question is '08 or earlier for sure, and was definitely cast by Motor Castings. It was more than likely machined originally by Cummins recon, but may have been redone by someone else at any time. If you weren't around back then, everyone on Moparts hated everything associated with this division of Cummins with a passion, and complained about quality problems on a regular basis. If anyone dared to post they had a Cummins recon built crate engine that ran good, they were told that can't be true and it would probably blow up tomorrow. Cummins bashing was the norm, all day every day.

If you're looking for identifying marks on the block other than the couple mentioned so far, don't waste your time, there aren't any.
One of the things I personally always disliked about Cummins recon and the older blocks is all the part identification was on a yellow sticker. Peel off the sticker: Good luck, tear it down, get out your mics and calipers and figure it out. The so-called World blocks had laser engraving on front, near the bottom of the timing cover flange with the actual part number on it, to atone for that particular sin. The laser engraving was a suggestion I made, but don't know if someone else also made it before me.

To be transparent, you can't get me going on this stuff without a certain amount of useless drivel, so I hope it isn't too much trouble to sift through all
my nonsense and get whatever you need from it. If I simplify it too much and disregard the context, it either won't make sense or will seem like I am
BSing, so I tend to dump a little context in there where I can. I've got over 8 years of my life wrapped up in that stuff, so the whole thing is just a crazy context
to me.

Good luck with it no matter what you decide to do.

Thats my kinda "drivel" haha
I completely appreciate you taking the time to explain the longer version of things to show some context.
The motor runs and has survived the dyno and some performance use. So I'm guessing it's going to suite me well. I just don't have the knowledge of the Hemi blocks and heads like I do for the wedge motors and hated to go into this blindly just to have a Hemi for my roadrunner. And be here asking for advice 6 mo the from now when I few questions now can save trouble downstream. I'll do as was suggested and search for some of your other posts. Can't have you taking hours to retype answers to questions answered many times over. Thanks for the help