Remanufacturing a 2009 GEP 6.5 Optimizer...

[DieselDobro]

Question at the bottom of post!
Well...I thought I was on the road to a long and prosperous relationship with a 2009 GEP Optimizer long block purchased from a reputable source and "test ran for compression, oil pressure and leaks". I even had this outfit install new ARP headstands and diamond pre-cups.

Truck is a 1999 GMC K3500 SRW that has been reconditioned front to back. Got a pretty good sum of money in this tuck. Starting watching the oil pressure on my GM 6.5 drop to about 5 psi at hot idle and the transmission was shifting hard and speedo drifting above 65 MPH on the highway. I knew it was time to go into the last domain in this truck...the driveline. Curiously my GM Service Manual specs out 6psi as minimum oil pressure at hot idle. Guess the oil spray pistons really eat a lot of pressure bandwidth compared to flow.

Fast forward to the week before Christmas...

I spent two grueling weeks meticulously pulling my core support, engine, transmission, transfer case for replacement or rebuilding and had it all back together and running New Year's Eve/New Years Day. Even installed a new Rotomaster GM-8 style turbocharger, GM reman injection pump, AC Delco water pump, etc.

Engine block is a 2009 Navistar foundry product and the heads are 2013+ Dalton Foundry heads. All GEP OEM parts. Compression was reported to run about 545psi average and hot idle oil pressure was reported to be 50psi.

After installing two different instrument clusters, (new oil pressure sending unit involved, too),
and plumbing and installing a manual oil pressure gauge I came to the disappointing conclusion that the hot idle oil pressure was in fact around 7psi! Now it takes a while to drop...but drop it does! Starts out about 60psi at idle!

That's not all...
I discovered I had a head stud slightly leaking coolant at an external location. That's not so bad but what about the studs I can't see??
I decided to try adding AC Delco stop leak pellets piecemeal to try and stop the leak. Also discovered a significant amount (half to 1 quart) of coolant in the oil and changed the oil and filter.
One last nail for the coffin... after deciding there was nothing to lose at this point I ran and idled the truck for about 3 hours to circulate the stop leak. I pulled the dipstick to see if I could detect whipped oil/coolant and noticed significant blow-by escaping the dipstick tube! Pulled the oil fill cap and same story!
Well... that all proves it's curtains for this leg of this project.

In the mean time, I am trying to work out a fair resolution with the folks I bought this from. I don't want another used, tested long block because obviously the testing process used on mine was quite lacking in determining the real condition of the engine.

Wouldn't be so bad... but at fair shop rates I have about $2700 in putting a bad long block in my truck and getting another one back in...minimum!

I am considering:
New GEP long block with warranty
New GEP long block without warranty
Rebuilding the bad GEP long block I have now

My question for this group is...will all the internal engine parts spec'd out for a 1999 GM 6.5 work on a 2009-2013 GEP 6.5 diesel?

[sctrailrider]

You have asked a loaded question to say the least...


1 - do you love this truck enough to keep it for life or do you want to?


2 - With the cost of a "blue printed" rebuild you can purchase a NEW crate motor..


3 - Consider a crate P400, I have proven the differences are considerably different than GM or GEP.. and the cost of the two motors new are not that different..



I have 3 new P400's in my shop being built now for customers that chose this route because they plan to keep them and still the cost is much much less than newer trucks, and with good planing and modification's they can put out a lot of power reliably..

[DieselDobro]

Thanks for the reply! So... do the late model GEP engines fit up with the early model GM internal engine parts?

1 - do you love this truck enough to keep it for life or do you want to?
Yes


2 - With the cost of a "blue printed" rebuild you can purchase a NEW crate motor..
Depends on the deal I work out with the supplier of the bad used engine.


3 - Consider a crate P400, I have proven the differences are considerably different than GM or GEP.. and the cost of the two motors new are not that different..

I'm going the GEP route for sure on the new engine. I have a 4x4 and I already priced the $9k engine and the $1k oil pan. I'm up on the Optimizer...however, I don't see the value in the added cost of $3k more and the added weight of a P400 for my application over a new Optimizer. I haven't blown up a GM 6.5 to date in 21 years the way I ran them...yet! I'm hoping my GEP 6.5 experience would be the same...at least!

[DieselDobro]

No one has rebuilt an Optimizer yet?? Please help, I'm going nuts trying to figure out where to throw several thousand dollars!

[sctrailrider]

I've built several, what is it you need to know?

[sctrailrider]

The internals will exchange as it's the same block with "supposedly" better metal content, but their have been several that have cracked in the very same places the GM blocks have, as far as I know no one has sent metal off to be tested to compare ...



I can say for a fact the head castings are identical inside the water passages, only the P400 has a different casting mold and more metal..

[DieselDobro]

Thanks, Chris. That's what I needed to know! I can check it every which way for cracks with mag particle with great confidence to even know if I have a good platform to rebuild. Trying to decide new or rebuild.

[sctrailrider]

You should check the message I sent you ...

[DieselDobro]

Thanks to SCTrailriders tip...I am now the proud owner of a P400 that was sold through Peninsular Diesel and is claimed to have 18,xxx miles of light use in a non-towing (relatively speaking) Suburban. The details are a little sketchy from the owner but I can fill enough blanks in to know I got the deal of the year on this thing! Even has a cast aluminum modified oil pan for my 4x4.
A bow and hats off to Chris!