GEP P400 motor

Hummer H1 and Military Humvee topics

GEP P400 motor

Postby rickcrebbin » Thu 29 Jul , 2010 12:58 am

Hi all:

Cutting a long story short - I lost my motor a month ago due to a cracked #8 cylinder. After hunting around I decide to go with a GEP long block but GEP were on vacation for two weeks so finally I found an agent W.W. Williams - spoke to a great guy that helped me a lot. I had read a lot about the 6.5 variants and the P400 kept popping up as the hottest new GEP. My WWW guy had just sold one to another Canadian so I took the plunge and ordered a P400 long block just over a week ago.

Another of us was in the same predicament and he had ordered a regular Optimizer long block from WWW. When he found out about the P400 he contacted WWW then GEP to talk more and a GEP guy told him that the P400 doesn't fit Hummers only the new HMMWVs - something to do with the oil pan. Today my new Canadian pal just recieved his new P400 so I called him to discuss the fit issue - completely new topic to him with respect to Hummers although he has read about fit issues with other trucks. His P400 was custom built for his 95 non-turbo; 18:1 compression.

Tomorrow I'm calling GEP then WWW to try and confirm what the issue is. I have read on other H forums that P400s have been seen in Hummers. It is surprising that there is so little P400 discussion on the H forums considering our collective engine woes. I promise to update you with all I find but meanwhile is there anyone out there that has installed a P400 in a Hummer? If so please share!

My fellow Canuk and I can only think that there may be an issue with the UCP - other than that what is under the motor between the rails?

Any comments are most welcome.
Rick Crebbin
98 HMCS all factory options, 16.5" Cepeks, TrXus MTs, 9' AMG (Toth) ally roof rack, IbisTek rear wheel carrier, bigger bush bar, PIAA fog/driving lamps, Toth storage racks.
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Re: GEP P400 motor

Postby h1sp » Fri 30 Jul , 2010 9:23 am

ah .. I hate to hear about your # 8 issues.

Always a HUGE follower of your beautiful BIG RED rig.

Please keep us in the loop.

This will be a Great post with pictures and up dates.

Whats your estimated cost for this project?
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Re: GEP P400 motor

Postby chuck » Sun 01 Aug , 2010 7:51 pm

Rick,
Let me know what happens and I'll update the cracked block motor section.

what is the reason everyone wants the P400 block?
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Re: GEP P400 motor

Postby dailydriver » Sun 01 Aug , 2010 11:28 pm

chuck wrote:Rick, what is the reason everyone wants the P400 block?


Come on Chuck! It's the newest coolest thing and everyone has to get one now!

No disrespect at all to Rick, I had been following his posts and #8 issues for a while. It seems he was doing his research on a new engine before the 400 was brought to many Hummer owners attention.

The P400 has actually been available for a few years and a few pickup owners have used it as a replacement their old 6.5TDs.

Hummer owners are a weird breed. I love them but some are out there (you kind of have to have a few screws loose to be a Hummer owner anyway). We all know that Duramax and Cummins conversions were the sought after addition to trucks. Even if guys didn't need them they wanted them for the "status" of having a big power conversion. It seems now that the (not new) new P400 is shown to them they think that is the must have item that the truck is not complete without.

That being said, the casting is very robust on the block. It's supposedly built to handle 250 HP / 500 ft lbs comfortably, and last hundreds of thousands of miles. I would CONSIDER the P400 as a replacement and de-tune that thing all the way down to 195 HP for piece of mind.

I do wish Rick the best of luck with the engine swap and look forward to following the progress.
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Re: GEP P400 motor

Postby h1sp » Mon 02 Aug , 2010 9:54 am

screws loose ? you talkin about me :) :mrgreen:

I know what you mean, bigger better stronger ... yet Please remember, lots of the H1 owners are old school hot roders.

We have done all that jazz ... built up the motor, destroying the t-cases, transmission, replacing seals right and left, worked on the rigs all weekend long, missed the daughters dance etc.... Im speaking for myself ...

something that has lasted trouble free and dependable for over 10 years with normal driving, im putting it back STOCK. Its usually less money tooooo.

I love mods, but for some reason i have to keep my H1 stock .... i know .... "boring" :|
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Re: GEP P400 motor

Postby dailydriver » Mon 02 Aug , 2010 2:01 pm

h1sp,
You hit the nail on the head with that post. I too am an old hot rodder. Big blocks and Turbo 400s or Muncie 4 speeds in everything :twisted:
The Hummer is best left stock.

Here is a '55 that I built and sold years ago. 454 ci, fully manual T400, Ford 9" rear end, disc brakes.
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Re: GEP P400 motor

Postby h1sp » Mon 02 Aug , 2010 2:25 pm

Yum, Yum. Love them pic's.

Thats what im talkin about.

The power, the rubber smell of the rear tires and the sound as that dogg launches from the line.

yep, yep, yep... you can take the boy out of the hot rod, but you cant take that hot rod out of the boy.

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Re: GEP P400 motor

Postby GreenMeanie » Mon 02 Aug , 2010 3:26 pm

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.
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Re: GEP P400 motor

Postby dailydriver » Mon 02 Aug , 2010 4:01 pm

Thanks h1sp!

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.
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Re: GEP P400 motor

Postby rickcrebbin » Mon 02 Aug , 2010 10:17 pm

Hi all:

I've been away a few days. As stated the P400 is GEP's newest and strongest motor. When I blew my motor a month ago and started looking at replacements my timing was really bad as GEP/AMG were on holiday for two weeks from July 4th so I could not talk directly to GEP. Of no surprise to any one here I was not the only one suffering from a broken motor at this time. My two new friends Tom (Hawaii) and Rick (Manitoba) both contacted me with reps that work for W.W. Williams, a GEP agent in the States. Tom had already ordered a regular 6.5 long block and Rick a P400. I did some web research and then called WWW and ordered a P400 longblock - $5625 before shipping and taxes. I also ordered a new water pump and a gasket kit. I'm keeping the old IP but getting new injectors and replacing all the rubber cooling hoses. My truck only had 34k miles on it.

Here's my rationale; I love my 98 to bits but the motor is surprisingly gutless on the road and when towing considering the size of the motor. I researched this before I bought my truck - waited until the right turbo truck became available thinking that the turbo would make a big difference. Maybe it does. I can't imagine how worse things must be for my NA bretheren. Now I've had the truck for 4 years and have been active on a number of H forums I know that this is normal.

So finally my motor blows a hole in #8 and I join the club. Of course I've researched Duramax and Cummins swaps to death too. I should point out at this time that I pretty much broke - I was unemployed for 16 months and have only been working again since the end of January - this motor problem happened at a very bad time for me financially so I'm borrowing to pay for the new motor. To make matters worse the truck broke down away from home so it's at a reputable mechanic who will be charging me by the clock for my motor swap. It's a job I would have loved to do myself.

Back to the P400; it's a stronger crank and bottom end and a significantly beefed-up block. The whole motor is designed for an intercooler and other bigger-power options but I'm just getting the longblock at this time. I figured that if in the future I ever have money to spend on myself again, I could do a body lift and complete the P400 in all it's glory - not to hot rod it with mega power. I'd be happy if it drives and tows on the road equal to my wife's 99 Dodge Durango.

I will keep you all informed as things progress. At this time we are all waiting to find out what issues Rick has with his P400 installation in a 95. Before starting work he thought that there may be a few small fit issues; driveline protection and the flywheel cover - that was just eyeballing it and looking at the drawings. He has been busy this weekend so hopefully all is resolved.
Rick Crebbin
98 HMCS all factory options, 16.5" Cepeks, TrXus MTs, 9' AMG (Toth) ally roof rack, IbisTek rear wheel carrier, bigger bush bar, PIAA fog/driving lamps, Toth storage racks.
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Re: GEP P400 motor

Postby Snakeyes » Tue 03 Aug , 2010 1:26 pm

Hi Rick,

Just saw your post, really sorry to hear the news about the job and the Hummer. You're a class act and deserve better. Congratulations on the new job and I hope it works out well.

I have also heard good things about the P400 block. I vaguely remember some issues with the size and shape of the oil pan. Best of luck with the install and I am looking forward to pictures of your running Hummer.
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Re: GEP P400 motor

Postby rickcrebbin » Tue 03 Aug , 2010 9:13 pm

Hi folks:

It looks like I'll be getting some more sleep tonight. I just talked to Rick in Manitoba. He's already driving his 95 with a new P400 longblock. I don't want to steal too much of his thunder - he's got pics to share. Some important stuff:
- the old motor parts transferred to the P400 longblock without issue. Although the block dimensions are different, all the critical holes are the same size and in the same place with only two exceptions; the bell housing bolts and engine mount bolts are metric.
- the motor fit with a few small mods; the small part of UCP under the pan had to be bent down a couple of inches (Rick heated the tubing up and bent it in place. Rick's aftermarket flywheel cover had to be cut down a little at the bottom where it touched the pan. I do not know if this is necessary with the Hummer original.

Rick and I talked at length about our shared research about these motors. As stated by others earlier and on some other H forums, we are very well exposed to #8 and blown head gaskets but on other non-H forums there's lots of discussion about other bottom-end problems associated with 6.5 motors. Rick's 95 is not #8 prone according to everything we have read - his failure was at the bottom end.

I'll keep you informed about the progress of my project. Many thanks to Rick, Tom and all others who have posted regarding my queries.

Thanks for the kind words Snakeyes - Your contributions are sadly missed on the other side.
Rick Crebbin
98 HMCS all factory options, 16.5" Cepeks, TrXus MTs, 9' AMG (Toth) ally roof rack, IbisTek rear wheel carrier, bigger bush bar, PIAA fog/driving lamps, Toth storage racks.
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Re: GEP P400 motor

Postby axemann » Thu 09 Jun , 2011 1:28 am

Hi all

I have seriously been tossing up between the P400 offered by Dennis Sweeny with 300Hp and 639/lb ft of torque, and the Cummins 6BT, both engines I would have to use an Allison, The difficulties I face are with my truck being right hand drive, and that I don't want to fit a body lift, I would prefer not to fit a lift at all though I was prepared to sacrifice the 2" lift for Cummins, however I would have to re-modify my RHD conversion to fit the hydroboost on the right hand side, this would mean the airbox would be cut in size something I didn't want to do, although the 6.5 flows at 350cfm the modification would enable me to run a K&N Filter which flows at 760cfm, so although the air box is minimized the flow is not; however I have read why not to fit a K&N and have spoken to a former GM engineer here in Australia in relation to their testing on the stock paper filters vs K&N filters.

I can't decide between the cummins and P400, both engines have plus and minus's although a few questions I would like to know are;

1) The P400 engine is said to have all it's problems fixed, apart from the now forged steel crank vs the old nodular iron, what other bottom end differences are there?

2) The cooling issues are said to have been resolved, how?

3) What noticeable differences have you noticed powerwise for those (Rick) that have the P400?

Thanks in advance

Travis
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Re: GEP P400 motor

Postby chuck » Sat 11 Jun , 2011 8:54 am

Travis,
What did the GM engineer say about the air filters?
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