5.3 LS Engine Swap into Ol’ Blue 1971 Chevy Truck Part 2


Part 2 of my ’71 Chevy LS engine swap. In this part, I pick up my new engine and stick it where the sun don’t shine (my garage of course…).

Hmmm, so where did we leave off with Part 1….. Oh ya, I had sold my motor on Craigslist and was left with a truck in the garage that has no motor. Time to fix that.

Picked up my new-to-me 5.3 LS engine off Craigslist.

Picked up my new-to-me 5.3 LS engine off Craigslist.

This motor I picked up with the Honda-Hauler was from a guy I found on Craigslist. He sells LS motors on the side as a hobby/business (profitable hobby?). His process is that he gets the motor from the junkyard AFTER he gets a deposit from you, the idea  here is that most junkyards have a warranty/return policy that starts the day the motor is bought so if he waits until he has a buyer to buy the engine the warranty will last longer (genius!).

So I put down a deposit and got a supposedly 70K mile 5.3 LS Motor out of an early 2000’s GMC Yukon with a 6 month warranty provided by the junkyard. The Craigslist guy takes the wiring harness and reworks it to include the necessary fuses/relays then flashes the computer removing the anti-theft VATS (Vehicle Anti Theft System) and doing a slight performance tune. Since I was going to be bolting it up to my TH400, he just programmed the computer as if it had a manual transmission (no electronics in the TH400’s).

I also picked up a fuel tank that was out of an S10 ZR2 Blazer. Even though they had V6's, the pump should put out the same pressure.

I also picked up a fuel tank that was out of an S10 ZR2 Blazer. Even though they had V6’s, the pump should put out the same pressure.

I want to clear up some confusion here. I did A LOT of research on bolting the newer LS motor to the older style TH400 transmission, most of which just confused me even more. The truth is, this is possible and quite easy to do. If you get a 4.8/5.3 engine with a dished flexplate the ONLY part you need is a Hughes Performance HP3795 Transmission Adapter. The reason you need this is because the LS motors have a crank that is .4 inches shorter than the older Chevy engines. The dished style of the flex plate makes for the same bolt pattern, but the Hughes flexplate adapter spaces the crank out .4″ to make up for the shorter crank.

Still confused? Here are LOTS of pictures:

Hughes Flexplate Adapter on the snout of my TH400 torque converter. (this is needed because the snout on the center of the torque converter is what centers it in the crankshaft. This reduces the chance of vibrations/damage.)

Hughes Flexplate Adapter on the snout of my TH400 torque converter. (this is needed because the snout on the center of the torque converter is what centers it in the crankshaft. This reduces the chance of vibrations/damage.)

My 4.8/5.3 dished flex plate held up to my TH400 torque converter with the Hughes Flexplate adapter in the center.

My 4.8/5.3 dished flex plate held up to my TH400 torque converter with the Hughes Flexplate adapter in the center.

Notice the 3 bolt circle on the newer flexplate is a smaller diameter than the older style torque converter. No biggie, grab a drill/die grinder, a carbide bit, and elongate the holes to fit the larger bolt patter. This is pretty easy as the flexplate is relatively thin.

Notice the 3 bolt circle on the newer flexplate is a smaller diameter than the older style torque converter. No biggie, grab a drill/die grinder, a carbide bit, and elongate the holes to fit the larger bolt pattern. This is pretty easy as the flexplate is relatively thin. Try not to make the holes larger than necessary though.

5.3/4.8 dished flexplate bolted up to my TH400 torque converter after elongating the flexplate holes by ~.5"

5.3/4.8 dished flexplate bolted up to my TH400 torque converter after elongating the flexplate holes by ~.5″

I then bolted the flexplate back onto the crank and torqued it to spec.

I then bolted the flexplate back onto the crank and torqued it to spec.

Warning, make sure you use Locktite on the 6 flexplate bolts and follow proper torque sequence alternating side to side.

First time through torque bolts to 15 ft/lbs
Second round torque to 37 ft/lbs
Third and final round torque to 74 ft/lbs

 

Just for good measure I always mark bolts with a paint pen after I final torque them. This also helps as a good indicator if the bolt ever moves because the lines won't match up.

Just for good measure I always mark bolts with a paint pen after I final torque them. This also helps as a good indicator if the bolt ever moves because the lines won’t match up.

Close up of the Hughes Flexplate adapter. Lightly sand the bore on the crank then tap the spacer in with a rubber mallet.

Close up of the Hughes Flexplate adapter. Lightly sand the bore on the crank then tap the spacer in with a rubber mallet.

Ol' Blue 5.3 LS Swap

All the spacer does is provide proper crank stickout for the snout of the torque converter to slip into and center on.

All the spacer does is provide proper crank stick out for the snout of the torque converter to slip into and center on.

The only complaint I can even come up with on my Craigslist engine guy is that just before we hooked the engine up to the cherry picker, I noticed the MAP sensor on the intake manifold was broken off. Not a huge deal because it is a little plastic sensor that can be had for ~$10-20 bucks. The sucky part was that I was trying to get the little sensor stub out of the intake and ended up dropping it into the manifold deeper into the engine. So I got the fun task of taking the intake off to play hide and go seek.

Luckily the intake is reeeeeeeeeeely easy to take off and had reusable gaskets. So after I got the intake off I went to shaking it around to see if I could hear the little plastic piece rolling around. After pouring leftover gas from the fuel rail all over myself with no success, I determined that I should look elsewhere.

Luckily the intake is reeeeeeeeeeely easy to take off and had reusable gaskets. So after I got the intake off I went to shaking it around to see if I could hear the little plastic piece rolling around. After pouring leftover gas from the fuel rail all over myself with no success, I determined that I should look elsewhere.

Found you little bugger! Thankfully that valve wasn't open, so it didn't fall down into the cylinder.

Found you little bugger! Thankfully that valve wasn’t open, so it didn’t fall down into the cylinder.

Then I figured while I have the intake off, I might as well clean it off. So I made a custom shop-vac attachment and went to town with a screwdriver and putty knife (GENTLY, because the heads are aluminum and easy to scratch up)

Then I figured while I have the intake off, I might as well clean it off. So I made a custom shop-vac attachment and went to town with a screwdriver and putty knife (GENTLY, because the heads are aluminum and easy to scratch up)

Dropped the engine in and put in a couple bellhousing bolts to hold it together.

Dropped the engine in and put in a couple bellhousing bolts to hold it together.

Ran into a problem while trying to lower it into position though. The driver side manifold is interfering with the frame. Instead of modifying the frame I figured I would just modify the manifold. Easy right?

Ran into a problem while trying to lower it into position though. The driver side manifold is interfering with the frame. Instead of modifying the frame I figured I would just modify the manifold. Easy right?

Ya, it would have been easy until I broke the rear-most bolt off in the head.... So, I had to pull the engine out again so I could get to it with a drill.

Ya, it would have been easy until I broke the rear-most bolt off in the head…. So, I had to pull the engine out again so I could get to it with a drill.

Drilled into the bolt and put an EZ out in it. Thought I had it solved until the EZ out BROKE OFF......!!!!!!?????? The EZ out bolt removers are made of some HARD steel. Dangit.....

Drilled into the bolt and put an EZ out in it. Thought I had it solved until the EZ out BROKE OFF in the head also……!!!!!!?????? The EZ out bolt removers are made of some HARD steel. Dangit…..

So 2 hours later I am VERY frustrated, but managed to get it out by drilling into it with my die grinder and a carbide bit.

So 2 hours later I am VERY frustrated, but managed to get it out by drilling into it with my die grinder and a carbide bit. Then removing the broken bolt with another EZ out

So now the motor is back in the frame-rails and attached to the transmission. It is held up by a board on the crossmember waiting for me to fabricate some motor mounts.

So now the motor is back in the frame-rails and attached to the transmission. It is held up by a board on the crossmember waiting for me to fabricate some motor mounts.

I am now working on some emissions blockoff plates that I will cover in part 3 when I start plumbing and wiring the motor. I am also working on doing a full LED light conversion for all of the lights except the headlights (DOT approved round LED headlights are still too $$$$$$ for my budget).

 

    Ol’ Blue LS Swap LINK INDEX:

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