GreenMeanie wrote:I thought Chuck posted a pic of the P400 some time ago. I could be wrong but i though the Optimizer 6.5 and the GEP were the same thing with the exception of billet or forged cranks. I am going to try and find that pic or post.
There are a few differences between the GEP 6.5TD, Optimizer 6.5, and P400.
First GEP is just the name AMG gave the facility after buying it from GM. Aside from the block being cast to eliminate the #8 issue the GM and GEP is pretty much the same engine.
The Optimizer is built by GEP as well. The biggest difference between the standard 6.5 and the Optimizer is it uses Caterpillar engine management. There are are a few other differences as well such as the intake manifold.
The P400 is marketed as the 6.5TD with all the weaknesses and problem areas worked out. It's very stout and looking at the block it is very beefy.
Us Hummer owners are always concerned with the #8, PMD, and head gaskets on the late 90's 6.5TD. However reading other diesel forums, it seems the guys with the same model year engine in pickups, dually, work trucks etc. Had more issues with the block cracking at or near the main bearing caps, the web, the girdle etc. The P400 fixes all of the block failures.