Barn Find 74 K20 Build (LS Swapped Daily Driver)

[76k5blazerr]

Had a productive weekend. Got all of the wiring finished except for hooking up o2 sensors and MAF, got the other header on and all the new plug wires. Mounted the PCM. Finished the trans cooler lines. Hooked up the cooling system, using the radiator hoses from the donor and my stock radiator and fan shroud. Going to have to extend the opening on the shroud but it will work. Oh and put the front clip back on. The transfer case is still out but the parts should be here today for it. The real banger this weekend was yesterday after I finished all the wiring, I hooked the battery up to make sure everything was still working on the truck, (lights and all) and after that I turned the key on to prime the fuel system and check for leaks. At first I didn’t believe it was working because the pump was so quiet I could barely hear it. It’s a walbro 255. But it was working and incredibly, there were no leaks!! Then I couldn’t resist and I turned the key to see if the starter worked, and to my surprise, the truck lit right off! I turned it off pretty much right when it started because I didn’t want to mess anything up with still having some stuff unhooked but I’m super happy that it sounds like it’s going to run fine. Should be driving it here in a couple days.

 

[6872xtc]

Cool deal!!

What is your opinion on how the guy did your harness? Nice work?

 

[76k5blazerr]

Cool deal!!

What is your opinion on how the guy did your harness? Nice work?

I’m very pleased with it. Well worth the money. I do not anticipate having any gremlins to chase down. He completely stripped the not needed wires out of the harness down to the pins in the pcm connectors and reloomed it all in brand new loom and labeled every connector. Also added in a new fuse box for the engine and trans and an obd2 plug, and left all the AC wiring in on some nice connectors so when I eventually add AC I can just plug it in. Definitely knows what he’s doing.

 

[76k5blazerr]

I’ve been thrashing the last few nights after work to get this thing together, and I drove it for the first time tonight!! Since the last update I built a Y pipe to connect the new headers to the existing exhaust on the truck, installed my eBay cold air intake, put the transfer case back together and back in the truck, installed the driveshafts and hooked up the remaining sensors, o2 and mass air. The exhaust is not quite ideal but it will work for now. The pipe is probably a little small for a single exhaust (2.25) but it shouldn’t hurt anything. Also ran out of gas in my welder and had to switch to flux core so excuse the booger welds. I just didn’t feel like dropping another 400$ right now on exhaust when there will probably be more important things that come up on it that I’ll need to replace. The driveshafts fit perfectly. The air intake is alright, it fits well and it’s tight. I didn’t use the box/shield that came with it because it wouldn’t fit well, instead I just fabbed up a bracket off the inner fender to hold it in place and support it. Not bad for 60$. Wanted to use the stock airbox but couldn’t make it fit with a passenger side battery and the jack on the inner fender. Transfer case seems good after I replaced the broken front output thrust bearing and washer. It is not leaking (except for a little wetness around the tailshaft seal which is easy to do in the truck). Nothing else on the truck leaks either. Maybe my first old truck that has 0 leaks! The test drive went well, drove it up to the gas station. Trans shifts good and it runs smooth. Alternator is charging. I was thinking about driving it up to the mtns this weekend to go camping but decided I better shake it down around town first. I’m sure there will be little things I’ll have to work on from here on out but being my first LS swap I’m super pleased and proud of it just firing up first try and driving. Here are some pics.

 

[6872xtc]

Congratulations man!!

 

[skunked]

Nice job getting it back on the road.

 

[max 02]

Right on!

 

[76k5blazerr]

Been driving the truck the last 2 days to work and around town. It is doing pretty well. I haven't been getting on it too hard because I still need to install the transfer case brace that runs from the side of the 208 to the bell housing of the trans. Ive read mixed feelings about how critical it is, but I have one so I am going to install it. Just need the bolts, but taking it easy until then. I can feel that the truck has twice the power that it used to already though.

The only "problem" to speak of at this point is when I start the truck up, doesn't matter if its cold or hot, the first time i drop it into gear, whether reverse or drive, it bangs into gear pretty hard and the engine also revs up several hundred rpm and it wants to lurch forward or backward, but after 5 seconds or so it calms back down to normal rpm, and once its done that, it won't do it anymore for that trip, shifts between gears smoothly. The actual forward gears in the trans do not shift hard either. Im thinking maybe throttle position sensor or idle air control valve. Any LS guys have any recommendations. Like I said, other than this, it is running and driving fine.

 

[max 02]

I wouldn’t worry about that brace to much... Definitely put it on if you got it. But squares are the only trucks i’ve seen with them. Duramax, Cummins, don’t have them.
Although the Duramax and Cummins transfercase adapters have been known to crack! Lol!

It your adapter bolts are tight and the driveshafts are in good shape you will be fine.

BTW. Great job on the swap! Very cool rig!

 

[76k5blazerr]

Got about 700 miles on the swap so far, and 2 back to back trips to the beach! It’s doing great, happy to report that my fuel mileage has almost doubled and highway cruising is much nicer. On both of my trips to the beach I cruised between 70 and 80 mph, which it does very smoothly, and averaged 13-14 mpg. Haven’t tried cruising a long trip yet at more economical speeds, say 65-70, but I would expect it might break the 15mpg threshold, but I don’t care that much. I’m just happy that my range has increased from 150 miles on a 20 gallon tank to about 225. I also installed a beefy class IV receiver hitch the other day in preparation to tow my 24’ Pursuit, which I just bought a new trailer for. It should come in right about 5k lbs. with the trailer and a full tank of fuel (125 gallons). I am hoping the truck will handle it fine. The LS has a whole lot better power than the old 350, and obviously I will not be towing in overdrive. We will see next week when I pick up the trailer.

Next up for the truck is a new retro sound stereo and 4 new speakers. Want to keep the dash looking factory. Planning on 2 speakers in the factory dash location and a 6x9 in the corners behind the seat on both sides. When I pull the seat I also plan to pull the carpet to modify the floor to mount the shifter for the Np208. Also taking the truck to the guy who flashed my PCM when I get home from the beach to have a “street tune” done on it. From what I understand he will drive the truck around with a laptop plugged in and optimize the tune on the engine and trans to get it totally perfect. Don’t have any cool new pics but here’s a few of the hitch installed.


And here is a question I just thought of for the LS gurus. I picked up a vintage Sun Super Tach the other day on eBay for this truck, the guy says it works. I hooked it all up and I got the backlight to work but couldn’t get the needle to move. It would barely wiggle when I first cranked the truck but that was it. This is with it hooked to the tach wire in my reworked harness. The guy who built the harness said it should work with an old school tach but he wasn’t sure. I’m thinking maybe it’s not sending out the right signal, like a distributer/coil would. That or the guy is lying about it working. Anyone know?

 

[skunked]

Some tachometers have the engine size (4-6-8 cylinders) via a switch or a wire you cut on the back. Have you checked that?

 

[76k5blazerr]

Some tachometers have the engine size (4-6-8 cylinders) via a switch or a wire you cut on the back. Have you checked that?

No I have not but being an old unit I don’t think it has that, I didn’t notice it at least when I was installing it. And it was previously installed and running in the sellers truck.

 

[skunked]

No I have not but being an old unit I don’t think it has that, I didn’t notice it at least when I was installing it. And it was previously installed and running in the sellers truck.

if it was running with a V8 before then it’s probably ok. I made the mistake once and it displayed low so I thought it was worth a mention.

 

[Truckman4life]

https://www.autometer.com/media/manual/2650-1563.pdf The last 2 pages are about tachs and LS engines. I thought I remembered that they needed to be set to 4 cyl and that's what Auto Meter says. They also say older tachs might need a 5 volt calibration. I only skimmed it.

 

[76k5blazerr]

This will be a short update to make up for the last few weeks of nothing. But long story short, got the truck “street tuned” 2 weeks ago by the guy who did the initial flash on the PCM and he fixed all the issues with the tune, optimized the engine and trans etc. Got it 100% dialed. That’s the biggest mechanical update I’ve got, other than that I’ve just been driving it. Been getting a steady 13-15 mpg. Over 1k miles on the swap with no complaints.

And here’s some eye candy. Do I even need a caption? That’s a freakin rig. Tow report coming soon, 3hr trip tomorrow, roughly 5500-6k lbs.

 

[Chevy305]

Tuning makes all the difference

 

[76k5blazerr]

She tows!! Man, pulled the boat like a dream. I had expected it would but was also pleasantly surprised how well it did. Kept it in 3rd and went probably 65 max and the 150 miles went easy.

 

[76k5blazerr]

Happy to report with 2k miles on the swap, the truck has steadily achieved 13-14 mpg empty and 10 towing. It seems to be happy with the 4.10 axle gearing and the 35s. Only problem to date is a plug wire that burned on the driver side header and caused a misfire, quick fix. Other than that, it's killing it.

 

[76k5blazerr]

Update Time! Been a while, time has flown by as usual. The truck has been doing great since the last update, I think I’ve got about 8k miles on the swap now, and getting ready to turn 70k on the truck. I have pretty exclusively daily driven it since the swap. Put about 1k miles on it towing the boat this fall with no issues, and road tripped it almost 1k miles one weekend to go to a wedding! I have done a few things the last few months. First and biggest: Stereo! Picked up a Retrosound Bluetooth radio along with 4 Kenwood speakers from brothers trucks and their 6x9 brackets for the corners of the cab behind the seat and the double speaker bracket that fits in the factory dash location. I am super happy with it. Install went smooth and the sound is killer! It really cranks up. I have heard negative things about retrosound’s quality but I have no complaints so far. It’s a killer rig for <500$ in the whole system.

Before: (original AM unit)



After:





Also got some new cleats! Buddy of mine got me this brand new set of Mastercrafts at wholesale pricing, I love them so far. They are as quiet as the old BFGs but with the added good looks and functionality of a mud tire, and made by Cooper in the USA.



And last but not least, I restored my original headlight bezels. Thought about buying new ones but figured polishing and repainting the OG’s would better match the original vibe of the truck so that’s what I did, and I think they turned out great.

Before:



After:



Also, if any of you guys are on Instagram, I’ve started a shop page for my side biz where I post project updates on my personal stuff and customers stuff. @swrautomotive Give it a follow if you’d like, have some cool stuff coming up. Currently wrapping up an LS swap in a 76 blazer for a customer/buddy.

Happy new year guys!

 

[76k5blazerr]

Hauled my uncles ‘70 442 to the restoration shop I work part time at last weekend. Car/truck porn!!! He recently hit a deer. 250 miles, cruised 65-70 with no problems. Got lots of thumbs ups going down the highway. I freakin love this truck more every time I drive it! I also picked up a Bluetooth OBD2 monitor that works with an iPhone app and shows most of the stats that the PCM provides. I was really wanting transmission temp but of course that’s the one thing it doesn’t show. Regardless, having an accurate tach, speedometer and real time temp gauge was nice. I typically tow in 3rd gear and I was running right about 2800 rpm at 70. This is with 4.10 gears and 35s. At that rpm I almost think I could tow in overdrive as long as I was on mostly flat ground, since I think it would be around 2400 rpm, though I haven’t tried. I just like how the transmission never has to shift, or even unlock the converter for hills when highway towing in 3rd. This unit also gives you instant and average fuel economy readings which is kinda cool. I averaged 9-10 pulling the car. Best tank so far empty is 15. Oh, and I finally had the excuse to install my old school Montana mud flaps. I made quick release mounts for them using clevis pins and hitch clips through holes in the lip at the bottom of the bumper. So they can be installed and removed in seconds. No rock chips on the car after 250 miles!