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How To LS Swap a Square Body Chevy Series: Ep.1

Updated: Mar 27

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This whole series started off with some what of a Bastard Child of a Truck. I ended up with the truck practically by mistake.

At the time I was doing some side jobs; lifter replacements, head gasket repairs etc. Then this truck came across my plate, a 1981 (for the longest time I thought i was '85 until I saw the title) C20 Pickup. It was a fairly clean truck basically all original with a re-done interior. You know, the typical Square body of someone that took care of it.

The owner had quite the task for me: install a Small Block Chevy Where the original 454 once stood. I figured this would be easy enough, I personally don't work on SBC's or carbureted engines, but I've dealt with my fair share so i figured it would be all good. I quoted the guy, agreed on a price and trailered the beast home.

I then hopped onto Facebook and craigslist to start searching for a suitable engine. To my surprise people are still asking crazy money for an engine that' s been around 50+ years, i couldn't find a single complete 350 for less than $2k.

Now the guy I was doing the job for couldn't spend 2k on a engine, so I opted to start looking at used engines and pullouts, that's where i found a 350 which looked decent, the seller was asking 800 so i offered him $700 and he accepted. I went to go pick it up, the guy was friendly and seemed like he knew what he was talking about, he showed me some other trucks and engines and then fired up the one I was buying with some carb cleaner on a makeshift stand. It fired up no problem and i was on my way home.

I got the engine put in relatively easily, changed out intake, carb and some other gaskets got it fired up and drove the truck around.

I noticed the truck was smoking pretty badly so i added some thicker weight oil on the first change, I figured what was in there was probably sitting in the cylinders for a while and at the same time I changed out all the valve seals. The smoking was better, and i figured what was left would burn off so I gave the truck back to the owner and told him to let me know if it stops smoking in the next 50 or so miles.

He called me up a week later and said that the truck was still smoking pretty bad, I messed with it some more until he sent it off to a engine build friend to get inspected. Once the guy pulled off the heads he measured the bore circumference and my 350 turned out to be a 305.

Great. I was Duped, and worse than that so much oil was leaking past the rings that there was no cost effective way of saving it.

Being that it was my fault for not doing my due diligence on picking out an engine, I opted to buy the truck off the guy for $2500, which was more than the amount I had quoted him, and quite frankly more than I thought the truck was worth.

And that's how we ended up here. Obviously I could've got a 454 or a 350 or even a 383 for the truck but i refuse to pay those kinds of prices on a truck i never even really wanted and sure a 400hp big block sounds nice, but i know i can achieve that level of power and get 18mpg as well with an LS.

So that's my story on the truck, I hope you all enjoy the series and also, the truck will be for sale once its finished, so if your interested in that let me know!

In this Video:

Jovani Dante Griego Introduces the truck, the build and the plan for the 1981 c20 pickup LS swap.

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4.8 Pistons:

Engine mounts:

Cheap original Generic mounts: (They work but aren't he greatest)

C10 Specific Mounts:

TH400 Crank Spacer:

Gasket Set:

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