Duramax'n a 1971 Suburban?

[rockwool]

Hi everybody,


I'm new to this forum and here to ask you about converting a 1971 (7th generation) C-10 Suburban that currently runs on a thirsty 1980's 350 and TH700 combination. I've got to say that this site has got some excellent info on it, although I do have quite a few specific Q's that I hope you can help me with.


Background:
The car belongs to a friend of mine (sorry but I have no picture of the beauty at the mo) and he wants to throw a late 90's 5.3L Vortec LM7 and matching tranny (4L60E ?) in it. The reason he wants to swap is better MPG but also more power, so he's thinking about bolting on some rahrah stuff on it.

Me, being a firm believer in the wisdom of Rudolf Diesel since 2006, proposed that he instead should throw a Duramax and an Allison 1000 in it, specially since he's so concerned about MPG but also as he likes to boost his torque and power.

Money is of course an object and looking at Ebay there is a difference, although not that big. I did tell him that diesels hold their value better and probably will do so even more by the years, longevity etc, but he's really locked on a gasser and hasn't even bothered learning about the greatness of modern diesels.

* He probably has a 3.73 ratio, but is aware that switching to a 3.07 will do MPG wonders.

* He's NOT going to TOW any trailers.

* Southern Sweden has no hills.

* He's running wide street tyres (I will double check but probably around) 275/75/15's (~10" rear rim).


The problem:
Comparative information is hard to come by since Chevrolet, by not equipping many of their cars and trucks with diesels, seem to favor the dividends of Big Oil over us small people and our planet.

And Ive noticed that MPG comparison of trucks in between seems difficult due to a lot or factors, never mind against a Suburban, or comparing a Camaro to a Suburban. Me, not having any knowledge about trucks I find MPG testimonials truck owners to be insane, gassers and diesels alike.

Finally, I have quite many Q's about a Duramax conversion and a few more will probably come along the way, but I'm numbering them so it's easier for you guys to keep track of them..



Q's:
1. Which one of the Duramax's do you suggest?
- The LML seems technically fantastic (B20 possibility with a particle filter, etc) but $$$$.
- The LB7 seems the more fuel efficient than LLY/LBZ/LMM's IIRC?
- How much of a worry is the LB7's inherent fuel-in-oil dilution problems and is it fixable/costly?
- Anything else?


2. Is a 6-speed over a 5-speed Alisson 1000 a matter in his case?
- What combined MPG can he expect?
- What highway MPG 55/70/80mph?
- Same Q's as above but with a 3.07 ratio?


3. What ~MPG will he get from a stock LM7 + 4L60E (?) combo?
- Combined?
- Highway 55/70/80mph?
- What MPG from an LM7 with bolted on punch?


4. Conversion difficulties - Duramax and Allison?
- Engine/Allison mounts and fitment?
- Has it been done before on a 7th generation C-10?
- Any links or litterature that can help?
- Anything else to think about?


5. Conversion difficulties - LM7 and 4L60E? - Engine/Transmission mounts and fitment?
- Has it been done before on a 7th generation C-10?
- Any links or litterature that can help?- Anything else to think about, steering column etc?


6. I found this page: www.grimmjeeper.com/gears.html but what Transfer Case and what Underdrive do C/10 Suburban's have?


7. My friend worries that a Duramax will not have the nice sound of gasser V8's. Any comments or clips that you can enlighten us with?
- Currently he has a 4" (?) exhaust that brings good vibes to our neighbourhood.
- Any other performance product that you recommend for better MPG or raHraH?
- How much power and torque will the respectively two Allisons and the 4L60E take?





That was A LOT of questions but please feel free to make it easier by posting links to other threads or sites that can be helpful. Cheers!