6.5 in cucv Questions

[erasedhammer]

Eventually I want to swap in a GEP 6.5 NA, but I'm not looking to slap a turbo and turn up the fuel. I would like to get one of those drop in GEPs that humvees were using to replace the old 6.2. Keep it same power levels or near same as my current 6.2, but with a better block. Objective here is longevity and mileage (GM rated the 6.2 at 31mpg highway, attainable w/ 5spd?)
I do have some questions that I can't seem to find a straight answer to.

What sort of mileage difference is there between a stock 6.2 and a detuned 6.5? I hear the precups are the determining factor here (assuming same hp output from the IP).

Most likely I'll get a NA GEP out of a humvee so itll require changing from 24 to 12v for sensors, IP, glow plugs, ect. Sensors/glow plugs are easy, but is it best to get a new IP or convert an existing military pump to 12v?
Personally, I think it'd be cool to have the artic pump for other fuel choices.

I assume the 6.2 alternator/powersteering accessories bolt right up and be turning the correct direction? Not sure if any of the detuned 6.5s had the water pump spinning in the other direction.

 

[Sharecropper]

Everything on a 6.2 will bolt right up on the NA 6.5, however the serpentine belt engines use a counter-clockwise rotation water pump, where the V-belt engines use a clockwise rotation pump. Also, stay away from the idea of converting a military turbo 6.5 to a non-turbo engine, as the intake studs are at a different angle to accomodate the rear-mounted turbo. As long as you stay with a NA 6.5, you can move all your stuff from the 6.2 and every nut and bolt will match. Here's a photo of my current engine build using a brand new 2018 P400 6.5 long block with 1985 stuff installed.

 

[erasedhammer]

Everything on a 6.2 will bolt right up on the NA 6.5, however the serpentine belt engines use a counter-clockwise rotation water pump, where the V-belt engines use a clockwise rotation pump. Also, stay away from the idea of converting a military turbo 6.5 to a non-turbo engine, as the intake studs are at a different angle to accomodate the rear-mounted turbo. As long as you stay with a NA 6.5, you can move all your stuff from the 6.2 and every nut and bolt will match. Here's a photo of my current engine build using a brand new 2018 P400 6.5 long block with 1985 stuff installed.

P400 long block? Would love to do that. How did you get the oil pan to clear the front axle?

Yeah wouldn't dream of trying to convert turbo to na.

 

[Sharecropper]

P400 long block? Would love to do that. How did you get the oil pan to clear the front axle?
Yeah wouldn't dream of trying to convert turbo to na.

My truck has been raised 5". Plenty of room between the stock oil pan and axle. The special cast aluminum oil pan on the P400 only hangs down 1-1/2" lower than the 6.2 pan. After seeing your post I rolled under the truck and measured it to make sure I hadn't missed something. I don't anticipate any problems with the P400. I'm not sure there are any more P400 long blocks available. You might want to check with LeRoy in Houston. I believe he bought all that were left.

Here's a photo of the P400 long block right after being uncrated which shows the new GEP girdle and cast aluminum pan.

 

[erasedhammer]

Yeah getting into this game too late. All the good stuff is sold off.
I suppose a regular used optimizer shouldn't be too bad. Certainly a step up from GMs 6.5

 

[Sharecropper]

There was an article I saw somewhere which detailed the differences in evolution of the 6.5 blocks. I remember there were several years of problem castings, but seems like there were certain production years which were the best. Since you are not going to turbo it you shouldn't have too much trouble. You might want to reach out to Richingalveston. I believe he has a lot of experience with the engines and might can shed some light on the best castings to look for. I'd be careful of sourcing a "remanufactured" long block. Read the reviews and talk to as many people as you can. LeRoy is a good source for information and he will readily talk to you on the phone. Some of the bigger outfits like Kennedy want to sell you a race engine. If all you are trying to do is get a good reliable engine, educate yourself on the strengths and weaknesses of the specific castings and then get comfortable with an established rebuilder to produce a long block with that specific casting. Heck I believe Jasper offers a good engine with a good warranty. Just saying...

Hope this helps.

 

[erasedhammer]

There was an article I saw somewhere which detailed the differences in evolution of the 6.5 blocks. I remember there were several years of problem castings, but seems like there were certain production years which were the best. Since you are not going to turbo it you shouldn't have too much trouble. You might want to reach out to Richingalveston. I believe he has a lot of experience with the engines and might can shed some light on the best castings to look for. I'd be careful of sourcing a "remanufactured" long block. Read the reviews and talk to as many people as you can. LeRoy is a good source for information and he will readily talk to you on the phone. Some of the bigger outfits like Kennedy want to sell you a race engine. If all you are trying to do is get a good reliable engine, educate yourself on the strengths and weaknesses of the specific castings and then get comfortable with an established rebuilder to produce a long block with that specific casting. Heck I believe Jasper offers a good engine with a good warranty. Just saying...

Hope this helps.

I'm just trying to avoid gm blocks in general, shooting for optimizer. I was hoping to find a take out on eBay from a humvee.
Saw one in good condition on eBa for 3k. NA optimizer, shoulda bought it.

 

[erasedhammer]

Did a little looking around and looks like AM General has stopped production of the p400 in mid 2018. Looks like the last few optimizers are being sold for around 7k as long block or drop in. 6-5liter seems to have a good deal on a complete engine

 

[Sharecropper]

You can certainly do as you choose, however I strongly urge you to slow down and learn as much as possible about the optimizer castings. There were different castings which were better than others. Like I said, Richingalveston has a world of knowledge and experience on optimizer castings and he has always been helpful. And I will add, I would think twice before sending $3 grand for an unknown HMMWV take out. If you could find the correct casting, you could build your own (or have it built by a reputable builder) and know exactly what you have.

Just my 2 cents. Hope this helps.

 

[erasedhammer]

You can certainly do as you choose, however I strongly urge you to slow down and learn as much as possible about the optimizer castings. There were different castings which were better than others. Like I said, Richingalveston has a world of knowledge and experience on optimizer castings and he has always been helpful. And I will add, I would think twice before sending $3 grand for an unknown HMMWV take out. If you could find the correct casting, you could build your own (or have it built by a reputable builder) and know exactly what you have.

Just my 2 cents. Hope this helps.

Won't be purchasing anything for at least another year... probably be all gone by then anyways. Site said 506 casting.

I had a 2006 Turbo GEP, 599 casting. Very nice engine.

 

[Sharecropper]

If I had not found the P400, I would have probably got one of those Optimizers from Bostic in South Carolina. That's who you are referring to, isn't it? I would still talk to Rich before I did anything. He can tell you the right questions to ask at Bostic. Git 'er done.

 

[erasedhammer]

Will do when the time comes.

 

[richingalveston]

I will help with what I can. I purchased a new one to find out they are now being cast by dalton and not optimizer but that is on new castings not rebuilt motors. the motor would have to be a 2017 or newer cast for it to be a dalton.

 

[erasedhammer]

I will help with what I can. I purchased a new one to find out they are now being cast by dalton and not optimizer but that is on new castings not rebuilt motors. the motor would have to be a 2017 or newer cast for it to be a dalton.

Interesting. Whats the quality comparison between am general and dalton? if any

 

[richingalveston]

They are suposed to be the same, same webbing changes and the same metalergy changes. I had one issue with one of the heads. The valve cover bolt hole blew out the side, i had to have the head repaired. I beleive it was machined to close to the edge of the metal. It is possuible that to much rtv silicone got into the hole under the bolt but I don't think that was the only problem. IF so, more of he bolts would have had problems becasue they all had about the same amount of rtv in the holes.

I don't use rtv for valve covers any more becasue of my bad experience. The good news was I found a company in houston that could weld in a repair piece and drill and retap the bolt hole so the head did not have to be thrown away.

The motor is running now but I have not put many miles on it because I am making a lot of other changes to the truck. It should be on the road more often in the next couple of months. I am almost finished with the items that are keeping it from getting back on the road.

One thing to consider, if you are interested in the p400, you need to get one soon. They are discontinuing these and supposedly the ones for sale on the shelf are the last ones. they are not casting the p400 anymore.

 

[Sharecropper]

Interesting. Whats the quality comparison between am general and dalton? if any

Now..........you are educating yourself. Keep going.

 

[erasedhammer]

Saw rubberduck4x4 has two p400, 14k... way too pricy for me.

By chance do you know the dry weight of the p400? must be more than the ol 6.5

 

[0331king]

I will help with what I can. I purchased a new one to find out they are now being cast by dalton and not optimizer but that is on new castings not rebuilt motors. the motor would have to be a 2017 or newer cast for it to be a dalton.

Rich, I looked back through your install thread to confirm and must have missed it; but did I understand correctly that even the new P400s are sold essentially “as is”?

 

[Sharecropper]

Because I have a new P400 I will try to answer for Rich.

The P400 long block was available as a new crate assembly from GEP, the manufacturer of the HMMWV. The engine was designed and put into production for the new heavier, upfit armored HMMWV, however GEP lost the government contract to continue production of the HMMWV. Subsequently a small quantity of the P400 long blocks were released to the public. I was fortunate enough to have acquired one last year.

The differences between the P400 and a new 6.5 are many, including a forged crankshaft, forged connecting rods with cracked joint design, forged pistons with ceramic top coating, improved and strengthened oil and water passages, hardened valve guides and seats, and last but not least, an integral cast iron bottom end girdle with redesigned main bearings and caps which are integral to the girdle. Also the oil pan is heavy cast aluminum.

To answer your question, yes the long blocks were sold "as is", but why would you question the integrity of the assembly? Having said that, recently I saw a used P400 on Ebay that looked rough. The starting bid was $7,000. I didn't look at the ad again so I don't know if it sold or even got a bid. I would not have paid that much for a used engine, unless I was just wanting the parts to build another engine.

Before I installed the transmission and front end on my P400 long block, and with no injectors installed, I could turn the crank by hand. I have never felt such a smooth and free-turning engine assembly. Here's a photo -

 

[0331king]

Because I have a new P400 I will try to answer for Rich.

To answer your question, yes the long blocks were sold "as is", but why would you question the integrity of the assembly? Having said that, recently I saw a used P400 on Ebay that looked rough. The starting bid was $7,000. I didn't look at the ad again so I don't know if it sold or even got a bid. I would not have paid that much for a used engine, unless I was just wanting the parts to build another engine.

Before I installed the transmission and front end on my P400 long block, and with no injectors installed, I could turn the crank by hand. I have never felt such a smooth and free-turning engine assembly. Here's a photo -

Sharecropper, My concern would be the numerous issues that can come up. Much like the issue Rich had with the valve cover bolt hole. They are awesome well engineered motors, no doubt, but sometimes things get put together wrong.

Awesome build you have yourself BTW, I’ve scribbled notes and screen shoted countless things reading through it. Thanks for documenting it so throughly.