70 C-20 4x4 Suburban Father/Son project

[1leglance]

Great info Andrew....thanks for that.

Yeah Nick...I have actually been holding Martín my 14yr old back from digging into the interior & paint for the engine...he wants to make some $$$$

My concrete for the new workshop/carport gets poured in the am so I will finally have a place to play all my own. And our weather right now is great for playing vs wrenching.
Camino del Diablo & Old Iron runs in March
Overland Expo in May
lots to do while the wheeling weather is perfect, no sense in tearing a good thing apart I guess.

Now Nick...the next question is how long do you think it will take to swap out tanks/crossmembers and when are you free?

Oh and if I don't do the diesel swap can I still beg a new wiring harness out of you while I am in Aus this summer?

 

[locrwln]

Lance my friend,

I think I will chime in with my opinion if you don't mind. If power in not a big issue (I don't think it is with you). Stay with the 350, add the OD trans, and add fuel injection at a later date. I bet you will be happy with the mileage increase and the little extra off-road ability from a slighter lower 1st gear. In the end I think you will have a more durable vehicle. The more anyone modifies a vehicle the more chances of having a failure on the trail from a missed bolt or loose wire connection or a who-knows-what. I know this from experience. I am doing my best to avoid putting a Cummins or Hemi in the Ramcharger. But I really would like the extra power and mileage not to mention the cool factor.

Anyway if it were mine I would put the OD with the 205 in it, add GM throttle body injection. Also there are plenty of larger fuel tank options so the range issue can be fixed. Spend the cash on the interior and suspension. Besides if the price gap between diesel and unleaded keeps increasing you may never see any long term cost benefits.

Hope all is well!!!

As much as like diesels and modifying stuff I have to agree with ColoradoBill. Add an overdrive trans and FI to what you got now. You could do this in little stages and be out doing more research for your awesome trip reports.

I'm with these guys and your wife. I like diesels, but at the price of diesel and the costs of building one, you will never make that up with gas savings.

Jack

 

[1leglance]

Jack..I get what you are saying...
but there is more than just fuel savings at the pump..
using old motor/trans oil
using veggie oil
running propane also to save $$
greater mpg = longer range on trips...this is a factor in Baja more than anywhere else

All that said I am seriously looking at getting a 6.2 block that I have a good line on...building the motor at my wife's shop (very cheap that way)...and then wrapping it in plastic on a stand until something goes wrong with my 350 gasser

 

[bftank]

these kind of decisions are best made slowly and with lots of research. i agree with your wife and noibn. leave it running the way it is. put in the 40 gal tank and the 700r4 for now. get the burb cleaned up so your wife will ride in it. all the while researching your endgame.

i am a large supporter of a front solid axle, but maybe in your situation finding a late model gm truck or suv donor vehicle with a diesel and do a body swap would be a good idea. this would give you the lower ifs, and stronger frame, a 4l80 a 6.5 turbo, a ff 14 bolt rear, a 241 tcase. having a roller frame with all the components there to work on at your leisure so you can have a complete solid drivetrain to slide under your rig when your ready.

another thought would be use a set of automatic drop steps for the sub if you did lift it. i think amp research makes them.

 

[Larry]

maybe in your situation finding a late model gm truck or suv donor vehicle with a diesel and do a body swap would be a good idea.

Oh, please no! That is the perfect way to ruin a nice old Suburban. That would only bring on an entirely different bag of worms to deal with as the track widths are different, wheel bases are different and not a single body mount will line up. Way too much fabrication required to ever been durable. Not an ideal approach.

 

[GlennA]

I noticed you are running 33 inch tall tires. This truck probably came with 29 in tall tires from the factory. You have effectively lowered your gear ratio by about 15%. In my experience, when I have added taller tires without regearing, my fuel mileage has suffered. One of my Jeeps went form 19 mpg to 14 mpg when I went from 27's to 31's. A subsequent regear, 4.10 to 4.56, got me back to about 18.

Just my .02

 

[98dango]

I noticed you are running 33 inch tall tires. This truck probably came with 29 in tall tires from the factory. You have effectively lowered your gear ratio by about 15%. In my experience, when I have added taller tires without regearing, my fuel mileage has suffered. One of my Jeeps went form 19 mpg to 14 mpg when I went from 27's to 31's. A subsequent regear, 4.10 to 4.56, got me back to about 18.

Just my .02

Not always the same with V8 rigs my 86 went from 8-12 with 31 to 35 tire change 4.10s and no od she was screamin every where now its a nice fast idle and good mpg to boot

 

[1leglance]

On the gear ratio thing with 33's
I cruise 60mph (speedo pretty accurate by gps) and the engine running smooth, not lugging, not on the throttle hard.

4BT where are you located?

 

[bfdiesel]

Lots of ideas presented here. Mileage seems to not be the issue as much as fuel options.

Here is my .02 on the diesels. The ford C6 is a good trans but no OD and the AOD is not a great option for computerless. The fords are heavier than the 6.2 so a 6BT over the ford is hands down the winner as it also has greater reliable power.

The 6.2 is the lightest and cheapest to rebuild and require the least modification to get it into the burb.

All the diesels you are thinking about are going to work fine for you it is just the money to get it in there.

As for gas engines weight is not even a worry and you will be limited to gas, ethanol, or a LPG. The gas motors are way more limited in fuel diversity is the only problem.

Is the fuel diversity worth the diesel swap?

 

[thecarman]

I love my 6.2L NA Burb, but here's another vote for leaving the existing drivetrain, unless you are just looking for a project.

The way you describe your current gearing with the 33s, is it even worth swapping in the 700R4 with your existing engine? Would it be lugging in OD?

My 6BT swapped 79 crew cab has been sitting in my basement waiting for me to work on it (need to fix issues from the previous owner's swap that surfaced after I drove it awhile), while I use my stock 6.2 Burb all the time.

 

[1leglance]

I hear all ya'll.....

Lots to ponder...but since it is been a while since I posted and pics I figured it would be good to let everything know the rig is getting used on a daily basis.
I did a quick overnighter to help a buddy test out his new trailer

Oh and this is my current rear setup...

I used 2 pads as I was solo and could be comfy.
The 3 pelicans are kitchen, dry food, recovery/tools.
I put the pads on top of the cases to test how sleeping on a platform (with a drawer) would be. Worked great with still enough room to sit up and put my leg on.
Also the flat folding seats are nice for getting in & out of the side door.

 

[matt s]

I still say do it. People who say you won't come out ahead $$ should consider you are not talking about a 20% or even 50% increase in milage. You are likely to see 80-100% increase. This is not because the diesel is so great compared to a modern gasser, but rather our old boxy rigs with a carb and 350 are SO bad. I know my 71 blazer gets 12 all summer and 10 winter and that is tracked to every drop and mile, best I ever saw was one tank at 13.1. I have 33's and 3.73 gearing and run about 2500-2600 rpm at cruise with the th-350 tranny (60-65mph). I really considered a tbi swap and overdrive tranny but just don't see me picking up more than 2mpg at most from that, perhaps a little better in winter. My 97 tahoe gets 15 on the nose and it's bone stock, I can't see beating that with a lifted brick of a rig. I am guessing you see 10 with the burb currently. Getting 20 with the 6.2 is not out of the question, perhaps a touch high for a suburban but I am confident you should at least see 18. Not to mention that with a 40 gallon tank and diesel your range offroad will be measured in days not miles.

BTW my MPG figures are based on total driving tank to tank fill ups. My daily drive is a mixed bag of 55mph single lane highway and a short stretch of freeway at 65. The single lane can be a little pokey and stop and go with traffic.

You have many things in your favor for the swap that most don't have. Besides, I was really hoping you would do it, so when I do it I have someone to ask questions of. :sombrero:

 

[1leglance]

And I am simply enjoying the rig right now
I have a freshly rebuilt 700r4/turbo/inj pump and I am waiting to hear on finding a good block.

The plan is to install the 40gal tank this weekend coming up..
Then when I get back from Australia (going for June & July) then I will install the 700r4 & transfer case behind the gas 350...at that point I will live with the rig for a while more and see if I still feel I need a diesel.
I hope to find a good block by then if not a complete engine so that I have it ready to go if I choose to do the swap.

Right now it is too handy a rig for everyday & short trips to mess with a tear down.
And the desert weather is perfect for getting out and no since in missing any play time.

 

[BCHauler]

I like your plan. Seems very wise to me.

 

[Deleted member 9101]

"if" I did a swap, it woudl be for a 6.2 diesel. They are cheap, easy to work on, and almost bolt right in and require minimal modification.

I have always been a fan of the 350, and with the right cam it can get plenty of power and not too bad of MPG.