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FirstGen 05-10-2004 10:11 PM

5.3 LS1 in my '68 stepside!?! Help
I am seriously considering a totally complete 5.3 liter gen 3 vortec/ls1 motor from a 2001 wrecked chevy with 4 thousand miles. Complete with computer, harness, pullies, assesories, fuel injection, etc. Only missing radiator and fuel pump (in tank anyway) and battery obviously.

Who has done this??? I know one member has for sure! Anyone else put a gen 3 block and computer in? My main question is how you wire the ignition and computer for this???

Please help I need to know soon.

Thanks for ANY info,
Taylor Sims

grayw0lf 05-11-2004 01:47 AM


A Gen 3 Vortec is not the same as the LS1. The LS1 is only available in 98 + up Camaro Z-28/SS, Firebirds, & Corvettes.

FirstGen 05-11-2004 02:34 AM

they are almost identically designed motors. the 5.3l vortec is referred to as a 5.3l LS1 because of all the similarities. but thanks for the education.

crazy4chevs 05-11-2004 11:01 AM

contact these guys, they should be able to help answer any questions.

FirstGen 05-11-2004 11:46 AM

Thanks for the link. The price is pretty steep though, $450 to re-work the wiring harness if you already have one. Hell I can get the whole motor for like 800 :confused:

Surely someone has gone through this before... Help me out

adamls 05-11-2004 03:19 PM

your computer will have to be reprogrammed to elimate things like anti-theft and if you dont get the tranny with it, that will have to be removed from the computer. The wiring is not going to be easy. There are alot of things you dont need.

68LSS1 05-11-2004 03:54 PM

Yes, the 5.3 and 6.0 are included in the LS1 family. Ther are externally the same size and parts are interchangable to some degree. John at Speartech is great and his work is of the highest quality. I'm not sure how similar the car and truck set ups are as far as PCM and VATS (vehicle anti theft system), etc but I can tell you about a LS1 swap. You can do the harness yourself. You WILL need the Helms books for the year of vehicle it came out of for the pin outs of the PCM. For a LS1 swap you can delete the rear O2's, fuel level sensor, air pump/egr, oil level sensor etc. You will alsi have to wire in the diagnostic connector which John sells. But you then will have to send the PCM out to have these items deleted or it continually sets codes. Same thing with VATS (it will not start until VATS is removed). Or you buy LS1edit and do the programming yourself (which is around $550.00). The only other option is a stand alone set up like Accel DFI or FAST but they are around $3,000 for those. Again I'm not sure how much alike the 5.3 truck set up is but I'm sure it's similar. If yu can find out about the VATS in that year truck maybe there is a BCM you can pull and use to take care of that (probably need ignition switch also). Not worth the hassle and extra wiring if you can get rid of it.
I don't want to discourage you from this swap as the LS1 engines are great but don't forget you will need a whole new fuel system, a 300.00 box to convert the digital speed sensor signal to something your dash can use (or go aftermarket speedometer/tach) among other things. Good luck.

Vince M 05-11-2004 05:19 PM

The 5.3 has different accessory locations than the 5.7L and might cause additional interferance. You'll have to come up with some motor mounts, cut the frame a bit for clearance, change driveshafts, etc....
There is a board member that emailed me a while back that was doiing this swap (5.3) but I don't know his board name. I'm sure he can add more.
You can also check out Street and Performance at

FirstGen 05-11-2004 07:37 PM

Thanks for the info guys! I was actually planning on using a TH-400 or 700r4 with an adapter plate from Advanced Adapters and keeping the mechanical speedo operational. And I was just planning on using a high pressure (EFI) inline fuel pump on the stock tank or a blazer rear tank, would that not work? Motor mounts probably wouldnt be a problem I think I can fab up a plate or something. I assumed I could use the same drive shaft and everything, why would I need something else if I am using the same tranny?
What does it cost to have the PCM programmed to remove the not needed mentioned stuff? As far as the VATS, what is the BCM?

I don't think the accessories are any different on the 5.3 than the 5.7 because alot of the Camaro/TransAm guys swap to the 5.3 heads to get higher compression. Maybe the assesory brackets are different but definatly not the thread holes. I'm pretty sure they is plenty of room under the hood for everything! :D
Again, thanks for all the help...

crazy4chevs 05-11-2004 09:33 PM

Check these guys out they have the conversion motor mounts. They also have a tailshaft for the 700r4 that can run the mechanical speedo and has a spot for the comp to hook up at the same time as well.


FirstGen 05-11-2004 11:07 PM

awesome site, looks they have it covered. I might have to abandon this whole idea though if there isn't some way to take care of the electrical and computer reasonably. The whole idea was to put in one of these because of the great price I found one for (800 complete with 2400miles). I sure would love to make it work!

For those of you that have done it, are there any problems with the oil pan or assesories fitting on these motors?

Thanks again,
Taylor Sims

99-2door 05-12-2004 05:05 AM

Yeah, you can get the engines pretty reasonable, but adapting it to an older trucks takes lots of extra cash. You can 't use an inline fuel pump. The fuel pressure must be kept constant on the newer motors. This requires a return line to the tank also.

68C10STEPSIDE 05-12-2004 09:20 AM

has anyone tried using the Performer RPM LS1 Manifold & Timing Control Module .....#7118 with a carbarator to get around the fuel injection and computer?

FirstGen 05-12-2004 12:20 PM

no, but I've read a fair amount about the idea with the LT1's nothing about the LS1's... That kind of defeats the whole idea in my book anyway.

KutThroatKustoms 05-12-2004 02:07 PM

SOrry to bring up an old thread.

But yes, the accessories are different. The accessories mount differently on the intake. To use car accessories, you need a car INTAKE, if you goto a truck intake, then you need the truck accessories.

Yes, but swapping to stock 5.3 heads is pointless, pnp and new vlaves and they're the best stocker type head to use.

The motors are essentially all the same, except the ls1/6 is aluminum with sleeves. all of the parts interchange but some parts require more to make em work, but in the end, they will work. Since you're in Dallas, contact he's in San Antonio and he'll tune and get your PCM to work for your truck.

FirstGen 05-12-2004 02:35 PM

Thanks for the information everyone.

Bobby, if you didn't already know the main reason they go to 5.3 heads is to raise the compression to 10.8:1 on the 346 motor, considering that they flow almost identically with the same size valves. I didn't realize that they mounted dirrerenty on the intake, why would this cause a problem? Or would it?


KutThroatKustoms 05-12-2004 02:41 PM

Yeah, I know they go to raise compression. Just my porter when I had an 02 silvy with an ls1 and 5.3 heads, ported them and put in bigger valves and said they outflowed a pair of ls1 heads he just grinded on. :shrugs: :)

It would cause a problem b/c then you cant get your accessories to bolt up. the ones that will, will and if i remember right, its a tensioner that wont mount. I have thought of fabbing up a bracket that mounts to the intake and then also has a mounting point on the side to move it over, so car intake will mount truck accessories. I just havent really played with ls1's in about a yr, been concentrating on my suspension setups. So i'm not 100% if its a tensioner or something else.

FirstGen 05-12-2004 02:52 PM

You are saying the 5.3 heads outflowed some 5.7 heads when you put bigger valves in? Wow. That is sweet.
I guess I'm just not understanding the reason you would want to go to the car intake. You are just saying because the LS1/6/X intake is far superior to the truck intake? The motor I was looking into is fully complete with all assessories now.
Thanks again

KutThroatKustoms 05-12-2004 03:05 PM

The comparision was.... a set of ls1 heads, ported n polished (gasket matched) and a little bit bigger valves and my heads gasket matched and valves bar3ly bigger then ls1 valves(i need to find the specs to get the numbers) and he said mine outflowed on the bench enough to make the 5.3 worth it over the 5.7..

As for the car intake.... the truck intake. like a 6.0 is more low/mid power... ls6 is the car intake to have, its more mid/upper, where the gen3 motors strive. Its not like a conventional small block where 5500-6000 was about it unless it was race.. Now, i'm now sure about the 5.3 stock rpm range, but an ls1, i know friends with just bolt ons and cam and going up to 6500 rpms, and it loves it, not loosing power. The 5.3 is a nice motor, but lacks the cubes, which is why a lot of ppl start with a 6.0 block, more cubes and a steel design, for strength but a little more expensive then an ls1. But with your 5.3, you can turn it into a great motor, using OE parts inside. You can work the heads, get a 6.0 intake if you wanna keep the truck accessories, 01-02 ls6 cam and springs (you can use stock retainers), bolt ons, tuning, and have a really nice motor.. if you need more, the motor will take a 100 shot all day long.

FirstGen 05-12-2004 08:47 PM

simple enough... pretty much what I was thinking also.

John @ BROTHERS 05-13-2004 01:02 PM

Some pictures for you guys.
2 Attachment(s)
Here are a few pictures of a 5.3 LS1 installed in a '71 Chevy. This was at our truck show last year and I snapped a few pics. Thought you guys might want to see what it looks like installed.

FirstGen 05-13-2004 02:55 PM

Looks freaking CLEAN!!!

Vince M 05-13-2004 05:28 PM

There is a LS1 intake comparison in the new High Performance Chevy mag that includes the 5.7L, 6.0L and others... all else being the same. Some interesting reading if you have the time.
The guy I was talking to about the 5.3...wish I could remember his name...said the motor mounts from Street and Performance won't work with the 5.3 because of interferance with the accessories. I think it was because of the alternator or the A/C which are down low. I made my own mounts out of some F body ones. I just cut them up and rewelded them when I had the motor and tranny in the right place. One thing to note about the tranny location. If you keep it in the same spot so as to reuse the drive might have interference with the pan and the cross member. Something to check out.

KutThroatKustoms 05-13-2004 05:41 PM

a/c on the car accessories hands down the lowest.

a lot of the ppl for the 73-87 (not sure if your trucks are the same any up there) but they use the stock car mounts, but for the frame, it just takes 1 flat piece of metal, its how a friend made his work and with the 73-87 frame, you can run car a/c with a little notch. :)

FirstGen 05-13-2004 08:32 PM

Since you have been through this before, tell me if I am on the right track or not. I have a 2001 5.3 with everything and harness/PCM. So I find the schematics for the PCM outs and wire accordingly (grounds, all time hot, accessory) then I remove the rear O2s, the EGR, and the VATS on the harness? What do I do to remove them just cut it out or what? After that I send out the PCM to be 'tuned' and they remove the mentioned stuff from the PCM and along with whatever trans stuff I decide to do and I'm good to go electrically. Now will a standard radiator work or is there something different with the reverse coolant motors that need a different radiator? I have an electric fan. The motor mounts I think I can fab. The exhaust shouldn't be any big deal. Now the fuel, what did you do for the fuel system? Any tips here? I think that about covers it.

Thanks for your help,

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