New member C20 4.8 budget build swap questions

[DM72C20]

Hi,

It's my first time being part of a forum like this. I have looked through many build pages and liked a lot of ideas I've seen on here.

My truck is a 1972 C20 that I have had for a few years. It was originally from Nevada where its previous owner drove it back to Canada and did some restoration to it. I have taken the truck on some road trips to Chicago and out to Halifax. It's been a great work truck, hauling lumber to my workshop where I make furniture. The only real downside was the fuel economy which at its worst was around 5/6mpg and best ever was just under 13mpg. It also didn't have as much power as I had hoped from the 350/350 combo. So now it is part way through a LS swap with a 2009 4.8l with 4L60E is in its place. My retired dad and I have been doing the work, mostly him, with the intent to make it a reliable daily driver, with better mileage and much more power than was there. It is a work truck and not meant for shows or even going too fast though I do enjoy that. The build is on a slim budget with the idea to reuse stock parts where appropriate or to get modern parts that will do the job.

Some questions about the swap that I haven't figured out yet:

-what to do for the fuel tank? Behind the seat tank is out now, and I want to figure out what will work under the bed, ideally using the 09 fuel pump. Plastic would be nice to avoid rust. I read recently about 87-91 Blazer tanks fitting well but I don't know the flange size that the pump would go in.

-what to do about gauges? I like the original gauges better than new ones, but a Speedhut or Cable X is very spendy compared with a set of New Vintage or Dakota. I saw the thread about an S-10 gauge swap which could work.

-what to do about the rad? I could get the original one cleaned out, add a steam fitting and then somehow adapt the 09 fans to a fabricated shroud. My dad is a sheetmetal worker by trade so that's possible for him.

-how to even begin the wiring? The rats nest is off the engine and while I have looked through LT1swap.com, I still don't get how to go from rats nest to pin out charts and whatnot.

-who can program the PCM? Anyone know Toronto area guys that can do this? Send it to LT1swap.com? It's going to be stock, probably will run the stock cats and O2 sensors.

Any pointers would be great!

Derek

[LS short box]

So here's my .02.
1. Fuel tank. Tanks Inc. 69 Camaro EFI tank/255 Walbro pump with the fill behind the license plate.
2. Gauges I've used my stock dash with Auto Meter gauges. All electric. Speedo and tach controlled by the ECM.
3. Radiator. I like the dual pass radiators because it has the input and output hoses on the passenger side. Makes hose routing so much easier. Currently running a AFCO radiator.
4. Wiring. Junk the stock truck wiring and go with a new aftermarket wiring chassis harness. You need good grounds. No cracked or worn wires.
5. LS harness wiring harness. I'm no electrical guy so I buy a harness and ECM from a known supplier. I like Howell. Have used a half a dozen or so but there many other quality suppliers.
6. Can't speak to tuners in Canada. Must be a number of them.
Good luck with your project.

[mongocanfly]

welcome...nice looking truck..!!
an echo to what lssb said
fuel tank...
theres plenty of info on fuel tanks on this site

the gauges ..
you can use your stock oil and temp gauges..youll need a metric to standard adap for the oil pressure sender..drill and tap the pass side head at the back for your water temp sender..the ecm needs the sender that's on the drivers side
the speedometer you can use a Dakota digital convertor box to go from pulse to cable

radiator...
your stock radiator will be plenty for a LS engine...the steam fitting can be plumbed into the water pump or into the rad hose with one of the coupling made for this

wiring..
I agree, if your trucks wiring is junk, youll be money ahead to replace it now

LS harness...you can send your harness off and have it built if youd rather not try it yourself...but I also like to just buy a ready made harness..PSI and BP both make quality harnesses

ECM..
youll have to have the ecm flashed for it to operate...youll have to find a tuner for that,,and Id also recommend a chassis dyno once you get up and running...itll make a world of difference

hope you wont be disappointed with the 4.8...ive heard both good and bad on them from a power and mpg standpoint

[DM72C20]

Thanks! I love the colour and stance on it.

The 2009 truck was sold to me as having a 5.3 but once we got it back and looked at the RPO codes, it turned out to be the 4.8. I still expect it will be an improvement over what was there.

I don't think there is any issue with the 09 wiring, other than I haven't a clue how to get into working on it to get to the harness I need. Going to watch the LT1swap youtube series on it and see if that helps me.

[mongocanfly]

I'm guessing the 09 is a dbw engine,,,did you get the gas pedal and all that with the engine?

[DM72C20]

Yeah, got the whole donor truck minus a bed and hood and other non essentials. DBW gas pedal is already in place.

[MDPotter]

My thoughts:

3. Nothing wrong with running a stock replacement radiator. Don't get hung up on the steam inlet needs. I have a $200 radiator off eBay (cheap fans on it though) with the trans cooler and I just put a T into the heater hose loop and hooked up the steam line.

4. If you have the time and want to rework the harness yourself, it's not that hard. It just takes a lot of time and very little money. LT1Swap has all the pinouts and info for which wires to remove. I did mine myself and it works just fine, no issues. More info in my build thread, but I worked on it a couple hours every night and actually enjoyed it. Or, you can spend a few hundred $$$ and get a brand new one. Unless you just want to redo it yourself for something to do and to learn about it, you might as well buy a new one unless you want to save money.

5. Brendan is one of the cheapest options for reprogramming the PCM. That or you can buy HPTuners and do it yourself, they're all easy changes.

[truckdude239]

i useds an 1987 suburban with tbi fuel tank and just used an ac delco ep391 fuel pump inside the tank instead of the stock tbi fuel pump.

i ended up with a with a cold case radiator with fans after the griffin radiator i bought didnt make it 3 years and they wouldnt stand behind it https://www.coldcaseradiators.com/pr...mance-radiator
cold case also sells a fan and should kit for it somewhere and they have lifetime warranty

i used www.lsx-harness.com to rework my harness and flash the computer

i also installed dolphin guages i like the gauges but the back lighting in the tach and smaller ones is dimmer them speedo https://www.amazon.com/Dolphin-Gauge.../dp/B07KBDHMS1

i also used dirty dingo ajustble slider mounts and the stock small block mounts https://www.dirtydingo.com/shop/index.php?cPath=359_360

i have a 2004 4.8 4l60e in my 71 c-10 and i love it the thing will scream!!!!

[DM72C20]

Anyone know whether the 87-91 Blazer tank and EP381 pump will work with a returnless system which I believe mine is? I think that I would need to add a filter/regulator then? I found WIX 33737 as a part number for that.

[72MARIO]

Jason at Cains Auto in tillisonburg ontario can help you with your harness and pcm programming. He is very good and has a ton of completed swaps on the road.

I would just jump right into the dakota digital gauges I have the rtx and hdx and they work great.

[DM72C20]

Thanks. Appreciate local options.

The digital gauges look great, but I'm on a pretty strict budget with this.

As for the fuel setup, I'm probably going to use a 72 Blazer tank since the 87-91 Blazer tank won't fit in my frame. Mine is a C20 so maybe the crossmember is different? I have 24" in front of the crossmember and not enough behind for that 28" square.

I'm thinking I will adapt a MTS poly Blazer tank p/n 2042 to accept the 09 fuel pump module and then I won't need a return at all and get the modern ability to run it down to empty without concern. I'll run a separate universal sender since the ohm signal is different. Sort of like this but into a poly tank: https://ls1tech.com/forums/conversio...maro-tank.html

[72MARIO]

Originally Posted by DM72C20

I'll run a separate universal sender since the ohm signal is different. Sort of like this but into a poly tank: https://ls1tech.com/forums/conversio...maro-tank.html

Again if you look at the dakota digital gauges you dont need to change the ohm range of the fuel gauge. Add up the extras to make factory speedometer operate and a extra fuel gauge to get the factory gauge to work your not far off the vhx gauges.