New engine for the family truckster! - Page 5

**njsteve** · #41 07-12-2017, 10:25 PM

Here are the necropsy photos. We'll start with the rod bearings. Looks like the oil analysis was spot on based on the flaking of the outer bearing material and the wear in the second layer.

**njsteve** · #42 07-12-2017, 10:28 PM

and next, the mains:

**njsteve** · #43 07-12-2017, 10:29 PM

The oil pan was pristine. nothing whatsoever in the sump area. You are looking at an empty pan - not one full of oil - it's that clean!

**njsteve** · #44 07-12-2017, 10:36 PM

And now for the bad news...these block were notorious for developing cracks in the main web area emanating from the main bearing cap bolt holes and the sharp transition where it was machined for the mating surface with the main cap. A lot of guys consider this normal and rebuild the blocks using some type of main web girdle.

So it looks like my gamble paid off of buying a new AM/GEP engine off the assembly line instead of waiting to see if my engine was rebuildable. You can't buy the AM/GEP block outright (despite the many chinese knockoffs being advertised on ebay and elsewhere as "AM/GEP updated blocks"). The only way to get it is to buy a brand new engine off the assembly line or buy a used HUMVEE takeout from a military salvager - which you would then have to take apart anyway to verify its condition..

The easy way to find the cracks is to spray the area with brake clean and then have a camera ready as you observe it evaporate. The crack will weep oil out at the last phase of evaporation and be visible for several seconds.

**Crush** · #45 07-12-2017, 11:48 PM

Wow great detail

**Ryan1969Chevelle** · #46 07-13-2017, 12:20 AM

Boat anchor:-(

A team of engineers should be a shamed:-(

Ryan

**njsteve** · #47 07-13-2017, 01:12 AM

I believe they traced the cracking problem to the fact that they were machining the engine blocks while they were still too "green" and the tolerances were changing after the block had some seasoning to it. Hence the cracks in the corners where they join with the main caps, and the main bolt hole cracks. Remember that these are low rpm engines - under 4,000 rpm max.

Back then they were making these engines as fast as they could churn them out, and selling them as fast as they made them. When the military HUMVEES went to the 6.5, AM General bought the rights to the engine and completely redesigned it to get all the stupid issues solved - cracking blocks, cracking heads, bad coolant flow to cylinder 7 and 8 (exactly where my headgasket blew out in 2103).

At least I can pride myself on the fact that the inside of the engine was spotless - no sludge, grunge, or caramelized residue anywhere...and for a diesel no less! I guess that's what 22 years of oil changes at 3,000 miles can do. All I ever used was the Rotella 15W40 and AC/Delco or Napa Gold filters.

**COPO** · #48 07-13-2017, 04:53 AM

Great thread. Well done.

**njsteve** · #49 07-15-2017, 05:59 PM

BTW, let this be a lesson to not leave your tools out when you're done with a job...

...The wife saw the cherry picker in the driveway and got an idea to use it to pull out some tree stumps. It actually worked pretty darn quick. Kind of like pulling a tooth. Took maybe 10 minutes once it was set up, instead of 4 hours the last time she made me chop one out of the ground with a pick axe.

**Tommy** · #50 07-15-2017, 10:12 PM

resourceful !

Tommy

Dedicated to the Promotion and Preservation of American Muscle Cars, Dealer built Supercars and COPO cars.