Need advice on 1973 Suburban engine swap

[NM Guy]

I have a '73 Suburban with a 350 and 4 BBL. It is 4WD with an automatic transmission. I would like to do a straightforward engine swap (no changing driveshaft, etc. if possible) and need advice regarding engine, carburation, transmission or other items I'm not thinking of. The vehicle will be used by my daughter's family in the Pacific Northwest to escape after an Electromagnetic Pulse (EMP) if, God forbid, that should ever happen. The plan is to meet at my ranch in New Mexico and they have to drive 1500 miles over mountain ranges to get there, so decent mileage is important. I plan to investigate installing auxiliary fuel tanks and I'll need to get a small trailer for them to haul additional fuel as there will be none available following an EMP. I realize that I will likely need to change the rear end ratio to help with mileage and make other non-engine mods to help with this.

We all hope that the risk of an EMP is very small, so the Suburban will likely never be used for escaping an EMP. Thus, I would like to have fun with it when my wife and I visit their area which we frequently do. For example, we have a small (20') travel trailer there that I would like to be able to pull with the Suburban and take the grandkids camping and fishing. For that purpose, I'd like to have reasonable power which is why I was thinking I would NOT downsize on the engine but would very much appreciate everyone's advice on that. They live at sea level but there are mountains close by. Power diminishes significantly with altitude and my son-in-law or I may need to stop and adjust the air / fuel mixture along the way while driving in the mountains. I would like to avoid any significant electronics as they will likely be toast after an EMP. I wouldn't mind having electronic ignition as I would store an extra distributor in a Faraday cage which is supposed to protect electronics from an EMP. My son-in-law could then swap out the distributor before leaving to join us.

So, here are my questions:
1. What engine and source for it would you recommend?
2. What carburator should I use (Quadrajet for its small primaries)?
3. I've read here that Vortec heads should be used. Is that right?
4. What other modifications to the engine should I make?
5. Other than having the transmission and transfer case overhauled, are there changes I should make?
6. As noted above, I know I need to check on the rear-end gearing but is there anything else along those lines to be done?
7. Any suggestions for sources for the additional fuel tanks would be greatly appreciated.

Thank you in advance for sharing your knowledge and experience in guiding me towards a good decision on this. I appreciate it!

 

[Frankenchevy]

1. l31r is pretty straight forward. it's the last 350 before LS. just get it from summit or jegs.

2. quadrajet is pretty decent on fuel. some people love them some dont.

3. the l31r is a vortec roller block, it will come with vortec heads.

4. none specific that i know of.

5. you need to post what trans and tcase you have.

6. ratios in diffs need to match front and rear

7. if your planning on hauling it around before the EMPocalypse, it'll need to be DOT legal. there are limits to how much gas you can haul in an auxiliary tank.

cant you turn the trucks garage into a faraday cage?

if your really worried about fuel economy, reliability and fuel shortages, you should consider a 12v cummins. properly setup, it can run on different types of fuel, even vegetable oil. a p-pump cummins has no computers and only needs 12 volts and a fuel source to run. compression ignition perfected imo

 

[NM Guy]

Thanks so much for your quick and thorough reply! Unfortunately, I have the Suburban at my ranch so I can't identify the transmission and transfer case right now but plan to get it over the weekend. Are there numbers or identifiers on them that will allow me to identify the models? I believe they are the original ones. Turbohydramatic transmission.
Super catch on the ratios being the same front and rear - seems obvious now but I wouldn't have thought about it!
Is the DOT legal requirement just because I could get stopped? I don't think any inspection is required for licensing.
I don't really know how to turn a garage into a Faraday cage, but maybe it is possible.
The reason I was going to stay with gasoline is because any fuel will get old and the daughter's family has gasoline cars that can use it up before it gets too old. I have another Suburban, a 1984 with a diesel for my escape!

 

[4WDKC]

1. l31r is pretty straight forward. it's the last 350 before LS. just get it from summit or jegs.

2. quadrajet is pretty decent on fuel. some people love them some dont.

3. the l31r is a vortec roller block, it will come with vortec heads.

4. none specific that i know of.

5. you need to post what trans and tcase you have.

6. ratios in diffs need to match front and rear

7. if your planning on hauling it around before the EMPocalypse, it'll need to be DOT legal. there are limits to how much gas you can haul in an auxiliary tank.

cant you turn the trucks garage into a faraday cage?

if your really worried about fuel economy, reliability and fuel shortages, you should consider a 12v cummins. properly setup, it can run on different types of fuel, even vegetable oil. a p-pump cummins has no computers and only needs 12 volts and a fuel source to run. compression ignition perfected imo

4 stock engine blocks do not have mounts for mechanical fuel pumps not sure about the crate engine.. make sure it has a roller cam, zinc oil could be very difficult to find post EMP

5 I would put a nv4500 in it, better mileage than an non electric auto, 208 case would be fine unless you are planning to make your on path over the mountains.

6 maybe add a locker in the rear.

8 how much will this vehicle sit? ethanol gas and the biodiesel crap will go bad if it sits to long both can clog parts/lines and render the vehicle useless.

6BT 12V cummins is not a direct swap in and you will have to do a good amount of work to make it fit but, gets my approval and if I could afford it i would swap one in a crewcab.

 

[roundhouse]

I’d suggest a crate 350 if you want to stick with gasoline
Unless the one in it currently is still reliable

If you want to use diesel the 6.2/6.5 engine are ok , Cummins is the best but it come wrapped in a dodge

I’d Probabaly use electronic ignition and keep a old points dizzy in the vehicle as long as someone knows how to swap it
Or maybe use the points dizzy with the pertronix module and keep the points and condenser and voltage reducing wire in the vehicle

The old points use ~8 volts
Which isn’t enough to run an electronic dizzy
And they use a wire from the ign switch to the dizzy or coil with resistance built in to reduce the voltage


Gonna need a big bumper and locking differentials in both axles to push all the other cars that don’t run out of the way ,

And it will be a fat juicy noisy slow moving high value target on the road , so any plating or armored protection would be handy

Some night vision would be handy and a FLIR scope would be worth its weight in gold

Search YouTube for : “killdozer”

I saw a bullet proof BMW sell on bringatrailer.com for $12k recently
Which was less than what the windshield alone cost

I’d use 3/4 ton axles or Mayne one tons of you can find em in your budget

The ones from a cucv pickup are 4.56 ratio and have a locking diff in the rear

Also you could search pirate 4x4.com tow rigs and expedition rigs

and expedition portal.com for ideas

Don’t ask a question on pirate that can be found by searching a little bit
They don’t like that , you’ll get insulted in a hurry and don’t mention the daughter , or they will be asking for pics ....
But other than that , I can’t think of any other website with more members who are genius level fabrication experts who actually build stuff and do stuff , some are keyboard commandos probably still living in the moms basement , but most are real world experts at modifying and fabwork

But if having a driveshaft modified is a deal killer , work wise or budget wise you really need to rethink The Whole project

Having a driveshaft lengthened , shortened . Or yokes swapped is an easy job at a driveshaft shop ,




And for a bug out vehicle I’d want one that gets driven regularly
Maybe daily

Cause when something bad happens the odds of you being at home when it happens are nearly zero

And consider bugging out on railroad tracks , bike paths , rivers ,anything besides a highway , they will be clogged with non running cars and that’s where the predators will be waiting for you

Thought about dual sport motorcycles ?

 

[Frankenchevy]

Thanks so much for your quick and thorough reply! Unfortunately, I have the Suburban at my ranch so I can't identify the transmission and transfer case right now but plan to get it over the weekend. Are there numbers or identifiers on them that will allow me to identify the models? I believe they are the original ones. Turbohydramatic transmission.
Super catch on the ratios being the same front and rear - seems obvious now but I wouldn't have thought about it!
Is the DOT legal requirement just because I could get stopped? I don't think any inspection is required for licensing.
I don't really know how to turn a garage into a Faraday cage, but maybe it is possible.
The reason I was going to stay with gasoline is because any fuel will get old and the daughter's family has gasoline cars that can use it up before it gets too old. I have another Suburban, a 1984 with a diesel for my escape!

modern gas is bad in a matter of months, even with stabil. auxiliary fuel cells are regulated, I'm not sure if you can legally self build a trailer that holds any significant amount of fuel without having it looked at. but, from my experience, e10+ fuels won't last very long anyway. so you couldn't fill that tank up and keep it for very long without it absorbing water from the air. you could keep it sealed, but still not sure about long term storage of obamagas. if your kids live in a moist part of Oregon this will be exacerbated.

l31r is not machined for a mechanical fuel pump, but basic electronic fuel pumps are not computer controlled. I'm keeping a fuel pressure regulator, carburetor and mech distributor as a backup to my efi. then again if **** hits the fan, I'm not going anywhere unless I have to go pick up a family member.

if you start to change your trans or tcase, you'll likely need to change driveshaft length. lockers would be a good idea. np208 was good enough for full size CUCVs, id just make sure to have it professionally serviced if your looking at the vehicle as a life line. Ive driven and wheeled mine around for years and still haven't serviced anything. only thing I ever did up until recently was adjust the carb and change the engine oil. I'll be opening mine up to look inside soon. but it's never made any noise, feels tight as a drum and doesn't drip a drop of oil. it probably gets more stress than most tcases with my front and rear being locked up. albeit, people consider the np205 to be the stronger of the two units.

 

[NM Guy]

I am absolutely blown away by you guys. So very nice to take the time to offer your advice and expertise. Maybe when I get my project done I'll be able to help someone else with the knowledge I will have gained.

I'll try to digest this information and will likely have additional questions. Thanks again, I really appreciate it.

 

[1987 GMC Jimmy]

I brought up the EMP the other day. I really think this should be in our lexicon as Americans because it could happen. Not saying it will, but it’s foolish to think that we’re insulated from this or that. I’d keep spare fuses, flasher relays, a horn relay, a circuit breaker for the windows, fusible links, bulbs, some Sylvania basic sealed beams from Walmart to have as backups and a complete breaker point ignition system handy. None of that will break the bank, and a lot of it you can buy online or at Wally World. Someone the other day mentioned dry cell batteries, I believe. That maybe worth looking into. I don’t think there are any complex circuits in a ‘73 to worry with besides the aforementioned basics.

 

[Charlie]