1979 K20 5.3 Swap

[smurfasaur]

In the middle of my swap and figured I’d share some information with other people out there wanting to do something similar.

Truck is a 1979 K20 that I bought about 7 months ago for $1000. It had a wimpy 283 and a sm465 that ran for about 10 minutes then I towed it home. Decided it needed a new heart and overdrive since my plan is to make it my daily driver and found a 5.3 with a 4l60e on CL for $500. Had to drive 4 hours after work on a Tuesday to go see it and bought it even though it looked beat. Got a bunch of extra parts so I figured I’d have everything I needed. Engine and tranny ended up being complete junk and both needed a rebuild. Word to the wise - do what everyone says and get a low mile running pullout with all the accessories....

So everything was going good and then I broke my wrist, and had to put the project on hold for a few months. Now I’m healed and have the engine and tranny rebuilt, and test fit everything today. Fits a lot tighter than I was expecting and really low and far back. Didn’t get a pic before I pulled it back out but crossmember has about 1 mm of clearance with the front of the block and I put the power steering pump up o where it bolts up and it needs to come up by at least 1/2” or so. Also got under the truck and the front driveshaft is about 2” short. Was hoping to not have to change the length of the shafts...

Using dirty dingo sliding mounts and I haven’t heard of anyone having similar issues? I’m thinking of making some spacers out of 1/2” plate to go under the stock motor mounts that are bolted in the truck but I’m not sure if the DD mounts will work without changing the length of my driveshafts.

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[smurfasaur]

I’m thinking of trying to get some spacers and mod the DD slider mounts to come forward, but not sure if I’ll get enough movement out of them.

Anyone out there done a similar swap with the dirty dingo slider mounts?


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[smurfasaur]

DD slider mounts work! Got everything bolted up and torqued down yesterday. Thinking of turning this into a build thread.

Engine in

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Got clearance Clarence

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Spacers

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Going to get some polyurethane roof patch goop an stiffen up my motor mounts then on to the rest of the project. Still need to:

Finish wiring harness
Plumb fuel system
Install lokar shift linkage
Plumb tranny cooler lines and mount cooler
Drill and tap water pump for steam line
Figure out the tranny crossmember
Re-wire headlights using relays for the LED headlights I have
Cut holes in bumper for fog lights
Replace bearings in alternator
Go to pick and pull and get MAF sensor & throttle cable
Hook up exhaust
Hook up dakota Digital VSS sender


I’m sure there is more I’m forgetting besides just putting everything back together.

Hope to have this pile on the road by March. Side note, is 3/4” of travel enough for a slip yoke on front driveshaft? I read somewhere that all you really need is 1/2”.


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[Camar068]

Nice progress, lookin good.

 

[rpcraft]

Best advice I will offer you is to just replace your motor mounts, Either new rubber or poly. Putting goop in old ones isn't going to fix them, and once that LS starts wiggling around some it will finish what the 283 didn't

 

[smurfasaur]

Best advice I will offer you is to just replace your motor mounts, Either new rubber or poly. Putting goop in old ones isn't going to fix them, and once that LS starts wiggling around some it will finish what the 283 didn't

Thanks for the advice - I take it you’ve had experience with filling motor mounts with polyurethane? My mounts are actually in good shape, and the general consensus on filling mounts with poly roof goop seems to be overwhelmingly positive (by goop I mean something like 3M window weld) so I figured i didn’t have anything to lose by giving it a go.


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[rpcraft]

I think if you have rubber ones to start with then its a bad idea to try and fill in the blank space with anything that might be harder because then the rubber will just go to crap and it wont help to have the goop around it because it'll still be loose.

 

[roundhouse]

I had to use spacers on my motor mounts too

I used late model Camaro exhaust
Manifolds and they worked perfect

I flipped the fuel rails around on the engine
So the connections pointed to the passenger front of the engine

Takes a few minutes with a Dremel to cut some tabs off the manifold to get the fuel rail to fit backwards


And you’re right
Do not buy an engine unless you can hear it run before it gets pulled out of the donor vehicle

The best way to go if you have the space is to buy the donor vehicle and sell it after you’ve finished your swap

I bought an engine that was claimed to have 140k on it
After I got it I saw a VIN on the valve cover and ran a carfax and it had 275k on it

So just assume every word the seller speaks is a lie ,

 

[smurfasaur]

I used late model Camaro exhaust
Manifolds and they worked perfect

I flipped the fuel rails around on the engine
So the connections pointed to the passenger front of the engine

Takes a few minutes with a Dremel to cut some tabs off the manifold to get the fuel rail to fit backwards


And you’re right
Do not buy an engine unless you can hear it run before it gets pulled out of the donor vehicle

The best way to go if you have the space is to buy the donor vehicle and sell it after you’ve finished your swap

I bought an engine that was claimed to have 140k on it
After I got it I saw a VIN on the valve cover and ran a carfax and it had 275k on it

So just assume every word the seller speaks is a lie ,

I’m using 2010 camaro Long tube headers and the drivers side fits perfect we’ll see about the passenger.

If you flip the fuel rails around doesn’t that make the mounting tabs on the rails not line up with the holes? I may have to try that...

Buying a donor rig would definitely be the best way to go but unfortunately I don’t have space for that. Worst part about my swap is I bought the engine and trans then found out that a guy at work had a 5.3/4l60e with all accessories harness and computer with 39k legit miles on it that he wanted $3k for. I thought that was a little steep. I’ve spent almost 4 on rebuilding the engine and trans, should’ve just bought his and dropped that sucker in instead of doing things the hard way.

Anyone in WA that wants a low mile swap I’m pretty sure he still has it sitting in his shop.


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[smurfasaur]

I think if you have rubber ones to start with then its a bad idea to try and fill in the blank space with anything that might be harder because then the rubber will just go to crap and it wont help to have the goop around it because it'll still be loose.

Theoretically I can imagine how that may happen over time if the rubber is pretty deteriorated already when you goop them, but it seems like there wouldn’t be any acceleration if you’re starting with decent mounts. I dunno there’s a poop ton of people who swear by it. They even did it on Hot Rod Garage with the Bonemarrow project so it must be legit [emoji6]

 

[roundhouse]

I’m using 2010 camaro Long tube headers and the drivers side fits perfect we’ll see about the passenger.

If you flip the fuel rails around doesn’t that make the mounting tabs on the rails not line up with the holes? I may have to try that...

Buying a donor rig would definitely be the best way to go but unfortunately I don’t have space for that. Worst part about my swap is I bought the engine and trans then found out that a guy at work had a 5.3/4l60e with all accessories harness and computer with 39k legit miles on it that he wanted $3k for. I thought that was a little steep. I’ve spent almost 4 on rebuilding the engine and trans, should’ve just bought his and dropped that sucker in instead of doing things the hard way.

Anyone in WA that wants a low mile swap I’m pretty sure he still has it sitting in his shop.


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If I remember right the tabs line up
I think You’re cutting off some of the tabs that hold the plastic cover on the engine
Which I was able to still use

It’s been almost two years since I did it

The engine we got has close to 300k on it now
Smokes a little bit , but doesn’t seem to burn much oil , guzzles gas though so I think most of the smoke is from running rich

All he work and expense is in the modifications to your truck and to the wiring harness and computer

So if you have to replace the engine , used engines are available for ~ $500 everywhere

But I won’t make the mistake again of buying one that I can’t hear run before it’s pulled out of the donor car

 

[smurfasaur]

If I remember right the tabs line up
I think You’re cutting off some of the tabs that hold the plastic cover on the engine
Which I was able to still use

It’s been almost two years since I did it

The engine we got has close to 300k on it now
Smokes a little bit , but doesn’t seem to burn much oil , guzzles gas though so I think most of the smoke is from running rich

All he work and expense is in the modifications to your truck and to the wiring harness and computer

So if you have to replace the engine , used engines are available for ~ $500 everywhere

But I won’t make the mistake again of buying one that I can’t hear run before it’s pulled out of the donor car

Hmm I’ll look this weekend when I’m wrenching. I don’t have a dremel but I have other cutting utensils at my disposal [emoji48]

Yeah that’s true! That is a positive way to look at doing a swap with a higher mileage engine. Hoping that my freshly rebuilt engine and trans will last for as long as I have the truck but if i would ever switch it would be to a 6.2. My wife’s yukon has the 6.2 and it’s amazing.


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[smurfasaur]

So I got the passenger side headers installed and the O2 sensor bung is about 1/8” away from my front driveshaft. The collector kind of has a little swoop in it towards the driveshaft and is about 10” Long so I was originally thinking that I would just cut off about 8” of the collector and then get a flexible exhaust coupling with a bung welded into it for the passenger O2 sensor, but then I had an idea...

Since the drivers side fits fine with no clearance issues, what if I just splice the 02 sensor wires together and only run the drivers side sensor? I can’t think of a reason why it wouldn’t work, and from my google research it sounds like some turbo ricers have done the same thing to get around welding an extra bung into their turbo piping.

Anyone out there have experience in this? Apparently you can actually delete the O2 sensors altogether which I would’ve known about before I had BlackBear performance tube my PCM and delete the back O2’s VATS etc.


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[rpcraft]

My experience with O2 sensors is you want them pointed up as much as possible, and I had to modify my collectors a little to make it happen, but that was simply switching from a three bolt style to a v-band clamp, so I can rotate them as far as possible and then clamp them down.

 

[rpcraft]

Oh and don't delete the rearO2 sensor signals... It affects driveability and tuning by AFR.