5.3L LM7 Swap into OBS

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MrPink

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For the drop in and go scenario you need the little converter/flexplate adapter(ICT Billet 551165), I used ICT motor mount adapters(551628) and did my own harness. If your donor engine and harness are from a truck with a 60e then you don't have to worry about wiring the trans in as it will be plug and play. If the your truck/suv was 95 and older then you have to do some additional wiring. Your best bet is to spend the $ and get someone like Brenden form Lt1swap.com to tune out your vats and anything else you don't need. Look for companies or individuals that are willing to make you a 100% plug and play harness, if you are not fond of wiring. It's not the cheaper route, but it will be easier in the long run.
 

Kchevys

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I also used ICT mounts for my swap. I dropped a bone stock LM7 in place of a 350 TBI. Even in stock form the LM7 makes the two door so much more enjoyable to drive. Had to swap my fuel pump since mine was a TBI. At first, I went with an EP381. It had the pressure but for whatever reason I would have to cycle the fuel pump, turn the key off and on, a few times to get it to fire. Dunno if it was a bad pump or what. The EP381 was swapped with a Walbro 255 and problem solved. Cranks on the first turn.

I bought a standalone harness from PSI EFI and used an 0411. If I had it to do over again I would have used a Holley Terminator X setup. By the time I bought the harness, bought the 0411 and had it tuned I was not too far off from the same money. If you go standalone harness I would recommend PSI. Their harness was top notch.

Good luck with your swap!
 

CRF450R

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Are you sure you want to give up that low end torque them gen 5.3s need lots of rpm to really make any power would be alot of work too loose that 5.7 vortec low end I ended up with a rebuilt 5.7 with a custom cut Comp cam I had mine cut for more low end torque and have a bit of a tune done with full 3" dual exhaust no cats and I'm happy. I'd least do a 6.0 swap if I was going through the trouble. But I'll have to keep an eye on the project for if I ever decide to 6.0 my old girl.
 
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Hey,
I'm going to be swapping the 5.7 in my '97 Yukon (4L60E and 4x4) with a 2002 5.3L LS over the winter.
I know there's a lot of mixed info out there, and I was wondering what others' experiences were, things they wish they had done instead, and overall just recommendations and quality parts I will need to purchase.
Anything is appreciated I'm just an apprentice learning and would like to do the whole thing on my own.
Don't take your OBS harness apart till you are ready to start it. I screwed up and took the old one apart before I actually knew what I needed. Overexcited! I ended up taking one out of a used OBS to get it together. Scott
 

97Yukon4dr

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I will answer any questions you throw my way. My truck is more on the "race truck" side, then the street side, but I have a little knowledge about a few rhings that might be helpful. The only advice I would really give is PLAN FOR THE FUTURE! If you think you might even for a second about a turbo, plan for that turbo!!! (Fuel system, exhaust, etc) if you're gonna run a shot of NOS next year, plant for that! It sucks doing **** twice. Be patient, do your homework and research, buy quality parts when needed (don't be a complete cheapskate!!), read other members build threads as they have alot of ideas, suggestions, and out loud thinking going on (great resources), don't be afraid to ask questions, but search search and search some more before you ask, and have a blast building it!!!

James
I'm currently trying to figure out which cam to put into it. It will be a dd city and highway, I'm wanting it to have a good amount of power at lower rpm's. (Good power and good driveability). Im thinking of going with the SPDC SD0053 (205/210) and upgrading the springs with it of course. But there doesn't seem to be a lot of info on people's experiences with it, have you heard anything about it?
 

Wh4t3v3rs

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I'm currently trying to figure out which cam to put into it. It will be a dd city and highway, I'm wanting it to have a good amount of power at lower rpm's. (Good power and good driveability). Im thinking of going with the SPDC SD0053 (205/210) and upgrading the springs with it of course. But there doesn't seem to be a lot of info on people's experiences with it, have you heard anything about it?
I haven't.... I'm a Brian Tooley Racing guy when it comes to my cams. They pair their spring kits with them and its a nice little package. Personally, I believe the best resource is to just call the manufacturer. They made the part and usually can lead you in the right direction. Something to keep in mind is not to over do it!!! WAY to many people over cam! You're on the streets not the track, you don't need a 7000 redline or a 4500 stall! An LS motor can make 500 HP with just cam, intake (OEM or aftermarket), headers, springs, and a solid tune!! I know my answer is super general, i just don't know anything about your specific choice of cam manufacturer.
 
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Leeztruk

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I had an LM7 in my '80 C10. I used a BTR stage 1 truck cam with a valvetrain upgrade. Very docile around town and good highway manners. but if I wanted to "play", it became a sleeping giant. As said previously, you really don't have to go super large on cam sizing to make the LS motor respond. With my cam choice the engine was a real pleasure to drive
 

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L31MaxExpress

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Hey,
I'm going to be swapping the 5.7 in my '97 Yukon (4L60E and 4x4) with a 2002 5.3L LS over the winter.
I know there's a lot of mixed info out there, and I was wondering what others' experiences were, things they wish they had done instead, and overall just recommendations and quality parts I will need to purchase.
Anything is appreciated I'm just an apprentice learning and would like to do the whole thing on my own.
Sounds like a good way to make it gutless to me. Go with something bigger than a 5.3L. Even the 6.0L has less torque down low than the 350 does.
 

Wh4t3v3rs

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Sounds like a good way to make it gutless to me. Go with something bigger than a 5.3L. Even the 6.0L has less torque down low than the 350 does.
Man, I don't know, I personally think you're being a little overdramatic with the word gutless..... the 350 is tried and true, FOR SURE! But bashing on the LS, come on now!
 

MrPink

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I'd like to see the 350 make 400hp or so with just a cam and springs. The 350 in it's day was an awesome motor and for certain applications it still is, but to make the 400hp mark with a stock bore not very worked over 350 is unheard of. Advancements in design and cyl head flow are what ultimately doomed the 350. Yes you can get a worked over 350 to compete with a stock LS. But it takes a lot more work to get to that point.

I am shelving my 350 to swap in a LS for one simple fact, my truck is 26 almost 27yrs old. It's got an antiquated EFI system on it, it has 180k miles on a very well worn 350 and on a good day made 210hp at most. The LS I am swapping in while yes displacement wise it is 27 CI smaller it pushes out 270-295hp/315-335ftlbs in stock form, and with the mods I am planning I will see in NA form ~450hp/475ftlbs, Boosting it (Turbo) i'll see 600-700hp give or take. You cannot do that on a 350 as cheap as the LS. I think all in all in NA form I will have ~$2500 into the complete swap which includes trans (Th400), converter (3000stall), Cam (BTR Turbo Stg3), Valvetrain(BTR), Tuning(either myself or a local guy).

The LS is far from gutless. At this point stock for stock it is the 350 that will get walked.
 
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