7.8L Duramax - Diesel Forum - TheDieselStop.com
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post #1 of 7 (permalink) Old 12-26-2005, 11:03 AM Thread Starter
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7.8L Duramax

Does anyone know anything about the 7.8 Duramax?
My father-in-law is going to be ordering a new truck and right now he wants the 7.8 in it instead of the C7 Cat just because its a bigger engine. I personally think the Cat would give better milage and a better service life, but I'm not the one signing the check so I wont tell him what to do. I was just wondering if anyone here knows much about that engine and if it is of the same basic design as the 6.6L Duramax. Maybe just a stroked version?

Any information is much appreciated, Thanks.
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post #2 of 7 (permalink) Old 12-26-2005, 12:23 PM
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Re: 7.8L Duramax

The 7.8 Duramax is nothing like the 6.6. Its an I6. Thats about all I know about it off the top of my head.

But here is a website I found in about 30 seconds on Yahoo. http://www.shadetreemechanic.com/duramax_diesel.htm

Its not that technical at all but does have lots of pretty pictures.

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post #3 of 7 (permalink) Old 12-26-2005, 02:53 PM
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Re: 7.8L Duramax

If you want to know about the 7.8L Durmax, look up an Isuzu dealer and go see him. The 7.8L engine is an Isuzu, though GM may screw around with it to modify the HP and torque.

I entertained buying an Isuzu cab-forward with the 7.8L engine for towing my 5'ver....after seeing a crewcab I-6 diesel Nissan in Texas towing a 5'ver.

I visited the Isuzu/Ford dealer two years ago on the SW side of Dallas to look at one of these beasts. The 7.8L Isuzu is de-tuned so the HP is MUCH lower than the 6.0L Ford....down in the 200HP as I recall...and the torque was in the 500-550 ft/lb range...again as I recall. The salesman talked me out of buying one. He said the Isuzu would destroy my old kidneys (rides really rough) and the power, when compared to my '00 7.3L PSD was not there....said I would really regret it when I hit hills or mountains.

The engine looked like it was really set up for industrial/commercail use when you look at the air filters, etc. The salesman told me it costs as much to work on an Isuzu as a CAT and the parts were about the same costs as CAT parts.....bring money.

And on the crewcab model, which I wanted, you have to pull the entire cab off the frame to work on the engine. That would really be bad.

I suspect your advice re the CAT engine is sound.

Florida Ed

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post #4 of 7 (permalink) Old 12-26-2005, 02:58 PM
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Re: 7.8L Duramax

I would take the 7.8L Duramax. It's an in-line 6, the Isuzu 6HK-1TC. It is not related to the 6.6L Duramax V-8. The 7.8L has cylinder liners, a longer EPA rated service life than the C-7, and common rail injection instead of HEUI. It is a smoother running engine than the C-7. Cat parts are expensive, but so are Isuzu's, so there's no advantage there. As for fuel economy, I figure they are about the same if you compare like-rated engines. Also, the 7.8L is available up to 300 h.p./860 ft. lbs. this year.

Louisville Joe, L_Series_Joe, now Louisville_Joe.
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post #5 of 7 (permalink) Old 12-26-2005, 04:39 PM
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Re: 7.8L Duramax

I would think the 7.2 cat would also be at a much lower hp. Nature of the beast. If your gonna actually use it for work 90% of the time then you leave the wick down a bit to make it last 500k miles.
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post #6 of 7 (permalink) Old 01-01-2006, 11:46 AM
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Re: 7.8L Duramax

I know a guy that has one in his Kodiac that he tows his "Toy hauler" with . HE LIKES it a ton he says,, but we work for GM and he may think he is being "Brand Loyal" WITH THE . [img]/ubbthreads/images/graemlins/vomit.gif[/img]ISUZU[img]/ubbthreads/images/graemlins/vomit.gif[/img] motor... [img]/ubbthreads/images/graemlins/biggrin.gif[/img] nothing bad to say 'bout them,, just JAPANESE,,,, [img]/ubbthreads/images/graemlins/rolleyes.gif[/img]

Jim T.*48* SLAPS Co-Founder, 30.8 yrs RETIRED UAW 6/01/06, Now an ART (Specialists Flight Chief) with the USAFR 414th MXS Seymour Johnson AFB. My pics! '03 Dually pics!, New truck, 2011 F-350 SRW LB CC. White Platinum Lariat! 4x4

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post #7 of 7 (permalink) Old 01-02-2006, 08:18 AM
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Re: 7.8L Duramax

Another vote for the 7.8. They are less troublesome than the C-7/3126.

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