1972 K20 LQ4/4L80E Swap

[pilotXC]

I'm going to call it "done" at this point... Need to color sand a buff the paint on the bed some, but I had it towed to the exhaust shop on Thursday and drove it back to my buddies house after, so officially driving again! Man, so different to drive this engine in the truck versus the SBC engine. I only drove about 8 miles, but everything seemed good. Temp was really cool on the gauge, but nothing seems wrong, seemed normal when I parked and checked the trans fluid and fan kicked on a couple times while it was still running.

I'm very happy overall with how it all turned out. Paint is not that great of a job, I really rushed it and it shows. Should have known better, but kind of had to have it done this week and as I keep saying, it's far from a perfect truck anyway. I'm sure I'll learn to live with it and once my kids are a bit older, I can repaint it if I feel like I need to. For how much I drive it and what I use it for, it's good I think. If I had to do it all over, I'm not sure I'd go to all the trouble given what I use it for, but I think I'll enjoy it non the less and I learned a lot. I'll try to follow up with more details and part info I used in a later post. Here it is out of hibernation.

[mongocanfly]

Congrats on the 1st drive...

[Daaaanz67]

Congrats looks great. You will definitely enjoy this for a long time as I have been for almost 10 years. Definitely a different beast with the LS.

[pilotXC]

Here’s some more details on how I approached the build and each hurdle. Not saying this is the best way to do it, but it worked for me.

Engine Mount: As stated, used the Dirty Dingo mount and in retrospect, it was pretty good, not great. The pan BARELY clears the cross member, maybe it’s user error? It’s also not adjustable, but more on that later… It’s just ok. I had to mount it as far forward as the kit allows for any sort of clearance between the engine and firewall. Wish there was a better, more straight forward choice or this was really well made for the 67-72 4wd trucks. Should have researched a bit more maybe, but it worked out, just took longer than I anticipated.
Engine Cross Member - https://www.dirtydingo.com/shop/index.php?cPath=359_369

Trans mount: Engine mounts dictated that I had to move the trans cross member back about 3 inches and build a spacer to raise the transmission about 2.5 inches so it was at the right angle for the differential. Mine was about 4.5-5 degrees at the transfer case output shaft and 4 degrees at the differential. I also used the stock ’01 Suburban trans mount and made a spacer out of 2 1/2 “ square bar that bolted to the stock cross member.

Transfer Case: I used the NP208 transfer case and it worked out really well with the 4L80E. I got drive shafts, front and rear, that bolted right up. In that regard, the DD cross member and engine mount locations were positive as the location allowed me to bolt the transfer case up and the drive shafts didn’t have to be adjusted at all. The range selector and linkage also bolted up pretty easily and work well without having to make any adjustments. The linkage is adjustable, but I didn’t have to do anything in my application, just mount the selector in the cab on the tunnel and hook up the linkage. I just cut the carpet to fit the selector. I also used the Dakota Digital pulse sensor for the rear speedo output so I didn’t have to buy digital gauges, it works just like it did on the gauge and is much less expensive route to go. I retrofit the stock transfer case brace to work on the NP208 from the NP205 as well.
Pulse Generator - https://www.summitracing.com/parts/d...BoCGVsQAvD_BwE

Fuel System: I retrofit the side mount tank and used Tanks Inc. in tank pump kit (link below) that I got on summit and a universal fuel gauge sending unit. It was quite a bit of work, but I also deleted the aluminum RV fuel door, on both sides of the truck as well as the cab mounted tank fill hole, and used a factory aux tank filler neck I had to install. This seems to be working really well, but haven’t driven the truck enough yet to really have a perspective. I also used a Tanks Inc. filler hose that is 2” on one end and 1.5” on the other to connect the filler neck and the tank. I then used Russel flexible twist lok fuel line to run to the rail and the return to the tank. There is a vent in the filler neck and I got a vented locking cap to vent the tank. I used the screw on AN fitting at the rail and a summit fuel filter just after the tank on the supply side. This was one of the biggest projects to get this swap completed by far.
Pump/Baffle - https://www.summitracing.com/parts/tnk-pa-2?rrec=true
Filler neck hose - https://www.summitracing.com/parts/tnk-gh1520
Return fitting at rail - https://www.summitracing.com/parts/rus-644113
Supply fitting at rail - https://www.summitracing.com/parts/rus-644123?rrec=true
Fuel Line - https://www.summitracing.com/parts/rus-634163
Fuel Filter - https://www.summitracing.com/parts/sum-230131
Fuel Sending Unit (not the one I bought, but basically the same thing) - https://www.classicparts.com/1931-72...RoCPp4QAvD_BwE
Locking Aux Cap – Napa 703-1838

Electric Fans: I went to a u pull it yard and got a 2000 Windstar dual fan with relays and wiring for $38. I cut down the shroud to fit better and it’s a good fit and very inexpensive route to go that seems to work really well. Supposedly the larger fan is dual speed, but I learned that Ford actually put a resister on one of the terminals to fake it. I tried to test it and both + terminals it came on at the same speed, so I wired it to have the big fan come on as fan 1 and both as fan 2.

Radiator: I used the stock radiator from the truck. The Windstar set up is good, but tight with hoses on. Also the fittings on the LQ4 water pump are smaller than the radiator, but a helpful guy at Napa found a lower hose that reduces from 1 ¾” on the radiator side to 1 ½” on the waterpump side. Part number below. I had to cut a portion off the water pump side to get the length right, but fit great after that. The upper hose I used the stock version for the ’01 Suburban (same as a Silverado) and had to fit it over the radiator fitting, which wasn’t too bad actually once I got it over the lip and nice to just be able to go grab one if needed later. I ran the steam port to the heater hose location on the radiator as well with a brass 3/4 “ to ¼” reducer. Various opinions on if that is the most aesthetically pleasing or not, but the drill the water pump option I didn’t want to do, my friend said he did it and it didn’t work well, and this was the best “quick” and inexpensive solution.
Lower hose – Napa 7364

Throttle Cable: I used the Lokar cable, 36” version, and cut it down to fit my truck. I really liked it a lot, highly recommend it and it’s very smooth now that the truck is driving.
https://www.summitracing.com/parts/lok-tc-1000ls1u

Trans Shift Linkage: My stock linkage aligned exactly to the shift lever on the side of the 4L80E, so I just bolted it on. It actually shifts into all gears, including 1st. My linkage is pretty sloppy though and I need to see if I can get that sorted out.

Trans Cooling Lines: I spliced my existing trans cooling lines from the ’72 radiator to the trans cooling lines from the 4L80E with flexible trans cooling line and hose clamps. I was trying to reduce costs wherever I could and this was the easiest solution for me.

Wiring: I had a local place modify my harness and he did a great job. It was $450 for that and to re-program the PCM with the wiring changes. It came back to me with the “three wire” hook up. Battery (+), Ignition (+), and fuel pump (+). Grounds are on the driver side of engine and two on back of engine. I also had tach and fan 1 and fan 2 on mine. I read a lot and got a lot of advice on how to wire everything, especially the alternator. I posted a diagram already, but that worked out great for my own preference to have factory gauges work, maintain all the existing wiring and integrate the PCM. I eliminated the big red terminal block next to the alternator from the LQ4 and the 4g battery wire that ran from it to the starter as well. As I stated, everything functions, battery charges, ammeter works, etc.

Temp. Gauge: I used the existing hole plugged in the head on the passenger side with the SBC fitting. I ordered a M12 1.5 to 3/8 NPT adaptor from amazon. Just put Teflon sealer on the threads and worked perfect. Local parts stores kept telling me there was nothing available to adapt it…
https://www.amazon.com/Team-Performa...26TH2VAA6ZKF95

Brake Booster: My engine original had hydro assist so the brake booster on the manifold was plugged. Parts stores could not pull up the AC Delco part number and kept telling me I had to tell them what the threads were on the fitting… I just ordered it on amazon and got a hose to fit.
https://www.amazon.com/ACDelco-12559...omotive&sr=1-1

Air Cleaner: I got a cheap $40 version off ebay, works fine, but not amazing fit or anything.

Oil Pressure: I drilled and tapped the one on the back of the engine block, it was 1/8" NPT and works great. Wish I did it with the engine out.

Misc: Tons of stops at the hardware store for wire, bolts, nuts, screws, washers, etc. for various things a long the way.

I’ll finish my sheet with approximate costs, but I think total, I’m somewhere between $4k and $4,500 without the transmission rebuild to do the swap.

[pilotXC]

I'm having some issues with a hard shift from 1st to 2nd in the 4L80 trans, not sure what's up with that and not familiar enough with PCM manipulation of shift points or line pressure change (if that's even possible with the PCM) so I haven't driven it much because I'm worried about breaking something. Hoping I can get it to the guy that rebuilt the trans this weekend to have a look... Here's the cost, probably missing some miscellaneous stuff still, for my conversion including rebuilding the trans.

[TomMLSx]

If someone changed the torque management tables and you installed a shift kit, yes, it can bang the 1-2. You can reduce the line pressure in the tune to soften up the shift some....


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